Safe cruising speed

[daveheitz]

As the new owner of a beautifully restored 1934 Buick, Model 66C,

I was wondering what the safe cruising speed might be. Can I do 55-60 mph all day with out fear of throwing a rod or doing other damage?

Thanks so much.

Dave Heitz

[jerry burger]

dave,

as i recall your 34 is extremely low geared,around a 4.6 ratio.this with a 29" diameter tire gives about 1891 mph per 1000 revs.60 mph would compute to 3172 rpm.i dont know what oil you have,but 20-50 valvoline (racing)or equvilant will help reduce bearing heat.

[Guffin]

I should not drive over 80 or change to aluminum pistons and rod inser bearings. The thick rod babit may fail.

Jan

[NTX5467]

You might research and see where the power ratings (horsepower and torque) were, rpm-wise, on your engine. Then, using the mph/1000rpm figures, see where those two rpm levels would equate to road speed in high gear. That would give you a speed range to deal with.

In the middle '60s or thereabouts, I saw a general rule of thumb that sustained cruising speeds (without getting into higher engine rpm levels) could be about 80% of peak horsepower-rated rpm for best results. This would put the engine a little above the torque peak (for a V-8 engine of that era) but comfortably below the horsepower peak rpm. End result for a luxury car of that era would be about 80-90mph using that formula.

I suspect such a general rule might apply to almost any engine, but the key would be how it feels and sounds at these rpm levels. If it's "happy", you'll know it as there should still be decent throttle response at those rpm levels and no real strain when accelerating up hills--plus plenty of accel pedal travel left in the linkage. Again, how it feels is important as every vehicle tends to have a "sweet spot" of where it likes to run on the highway, speed-wise.

Other than engine issues, don't forget about BRAKE issues--their design and capabilities as positioned against what was the norm when the vehicle was produced and modern traffic patterns. Not to mention TIRE issues and their capabilities! Getting up to "a" cruising speed and maintaining it is just one factor in the whole equation!!

With the more modern oils of today, engine lubrication is not the factor it might have been when the vehicle was new. Seems like many of those older vehicles had engine oil coolers from the factory? A high quality 30W oil might work well, but the 20W50 alternative could work too--just watch the gauge and see how the different viscosities might affect oil pressure in the ambient temps you're driving in. With the lower power engine, the 20W50 oil could take more power to run the oil pump at normal operating engine temps, which might be noticeable in performance, but that can be a variable situation depending upon engine wear factors and such. Personally, I think I'd baseline it with 30W and progress from there. Almost any oil on the shelf will have higher specs than the oils of the era your vehicle was produced, so brand would be your judgment call (although we all have our own brand perferences, without turning this into a "You ought'a use ________ brand of motor oil" commentary).

Just some thoughts . . . "Happy Motoring"

NTX5467

[patp]

Dave,

My mother owns a 1934 buick 66 c that my father restored. Did not know of any others in the country. Perhaps my brother can answer some of your questions. I'm not used to boards but if you contact me I can give you his info.

[ply33]

Please excuse me for popping into a thread on a marque that I know little about. I have wondered about the same issues for my 1933 vintage car and have posted my thoughts here:

http://www.ply33.com/Misc/speed

I don't know about the internal construction of the Buick engine of that era but I assume it was a big step up from the Chevy. If so, then unlike the Chevy it should be able to maintain some respectable speeds. However, as another poster noted, the engine is only one part of the package. Your tires, brakes, suspension, etc. all should be considered when deciding how fast to drive.

[55PackardGuy]

NTX, as usual you have some interesting thoughts. I've found that the "sweet spot" is somewhat dependent on drivetrain as well as engine rpm at higher cruise speeds. Harmonics seem to play a big part in the smoothness of engines and drivelines, and listening for "sympathetic vibrations" and other anomalies can help you figure out what speed your car's particular set-up "enjoys." At least that's my observational seat-of-the-pants experience. I assume that the less noise and vibration the less wear and tear.

For example, the old '65 Electra I drove in the mid 1970's would start a driveline "roar" at speeds above 85 mph, even with CV joints and a split driveshaft. 85 was kind of the "magic number" for me in those days of often-flouted 70 mph speed limits. The mechanical secondary linkage on the 4-barrel would just be ready to open at around that speed, and you could feel it on the accelerator pedal. Running with just the primaries wide open seemed more "economical" to me--hah! When the folks were along, I could always expect to hear my dad complain from the back seat if I was going over 85, and that was because he disliked the driveline vibration and noise.

I've noticed this in my '89 Camaro, as the driveline vibration peaks at around 70 and starts to dissipate at 80, so I can either go a bit under the freeway limit or a bit over to smooth things out. Of course, being an over-powered little Chebby (350 TPI V8) it might have some driveline issues that need to be sorted out!

Do you have any experiences to relate on driveline balancing? Is there a procedure to balance the entire system for smoother performance?

[NTX5467]

Some great comments! The vibration/harmonic issue is a good gauge too as when the harmonics are quiet, you can presume that ALL of the major reciprocating driveline items (including tires) are in more of a low stress situation. ALL of those items have some balance operation applied to them at some point between manufacture and final assembly.

In the earlier days of tire balance, it was typically done with a simple bubble balancer that was (static balance?) very common and easy to use, but still required an active attention to detail by the person doing that function (with a few other tricks too). "Dynamic balance" was when the complete tire/wheel/brake drum rotation assembly was spun up on the car "to speed" (typically a Stewart-Warner Alemite product).

Tire truing was also around back then. It buffed/ground rubber off of the tire itself to result in an almost completely round tire, as mounted on the wheel at that point in time (dismounting for flat repair would require that the tire/wheel relationship be marked for reassembly in that relationship, which many did anyway so they would not have to rebalance the assembly after the flat repair). In their final quality control checks, you'd sometimes see "buffed" areas on the tires back then where something of this sort was done at the tire factory, but usually just in one smaller area. As it removed rubber from the tire's tread, it could also result in shorter ultimate useable tire tread life. Was more of a "high end" situation that only a few tire shops had the equipment to do.

Tire Matching came in with the later '70s and early '80s. As it was presented, the wheel had a "low spot" where the valve stem hole was punched, so the tires were all paint-spot-marked for where their "high spot" was. Matching the paint spot to the valve stem hole was "matched" and was supposed to offer the best balance and smoothest ride (from balance issues). For a while, it was "a big deal" and you could tell if the tire installer knew about it (really easy) or not. Tire sidewalls still have some paint ID on them, but I'm not sure if it's for that purpose or not. Of course, this was when electronic wheel balancers were just coming into wide use (including the budget models that relied on the operator to manually spin the tire -- with a crank handle).

Current higher end tire/wheel balancers are computerized marvels. Measuring wheel runout, tire runout, road force variation, PLUS balancing the tire/wheel assembly. Pretty bulletproof to use too, so long as the calibrations are accurate.

On the driveshaft side of things, there were many middle '80s GM light duty trucks that had some resonances/vibrations from the factory. The "fix" was to get a new assembly built by a reputable d/shaft shop. Another "fix" for the resonance was to drill a small hole in the front end of the tube and fill it with "two part expandable foam". It seems that almost all driveshafts, back then, had a piece of rolled cardboard inside of them for vibration damping purposes, not to mention diameter changes along the length of the shaft.

When the foam didn't fix the issue OR settled out and made the vibrations worse, we'd get a new shaft built. The new shaft, unlike the production shafts, would be all the same diameter from front to back and were completely new. Balance? They claimed it was not necessary. Why?? 1--The tubing stock was of consistent gauge and thickness 2--The yokes were all machined on their inner surfaces and were of consistent balance 3--As long as the whole assembly was jigged-up correctly and everything was square (no runout, or within very small specs) when it was welded, cooled, finished, and painted/tagged, everything would be "in balance". About 95% of the time, it worked as they said it would at a much more cost-effective price than a new replacement item.

Later, they began to do balance jobs, where they could get everything jigged up and just rebalance rather than always rebuilding per se. In our case, a whole new assembly was the only option, though. They usually included new u-joints when they put one up for diagnostics too.

In the case of 2-piece (or more on some GM Motor Home chassis vehicles), not only must the balance be "in spec", but ALSO the rubber isolators that the carrier bearings run in MUST be in good condition (not settled out or degraded/deteriorated) AND the angles of each driveshaft segment (in relation to the other driveshaft segments/transmission output shaft/differential pinion shaft) must all be within specs for the way the vehicle is normally loaded. Of course, the u-joints must be lubed and in good condition too!

On the carrier bearings, there are usually some metal deflectors that are assembled on the front and rear of each bearing. These MUST be there for good bearing life--even with a "sealed" bearing!!! I know that from earlier experiences with our '69 Chevy CST-10 when it was newer.

By observation, many of the driveshaft shops that are setup to do balancing will also be doing heavy duty truck drivelines (which also use multi-piece shafts). Only thing might be that their jig might not accomodate the length of a long wheelbase car two-piece drive shaft, but then that might be easy compared to the Motor Home chassis vehicles with much longer wheelbases and 3 piece driveshafts.

Other than u-joints, do not fail to consider the bushing in the tailshaft housing of the transmission (on rear wheel drive vehicles). It can wear and it's the wear interface for the front driveshaft yoke. Usually, though, when it wears, the additional movement allowed by the wear will degrade and "take out" the related lip seal in the housing too, causing a leak. Therefore, those two items need to be replaced at the same time or you'll soon have another leak if you just "treat the apparent" rather than also taking care of "the root cause" at the same time.

Also, when the driveshaft is removed, inspect the INNER splined surface of that front yoke for wear AND also the splined shaft of the transmission it slides over. Wear or "greater tolerances" in this area can contribute to the driveshaft clunk when putting the automatic transmission in gear, or going from "D" to "R" or vice versa. GM also has a blue "special driveshaft lubricant" that can help address this clunk or "sticking" noise (applied to the splined inner area of the yoke). It is a baby blue in color, Teflon fortified grease (1 pint can) and used to be about $35.00/can. It was originaly done to address the "driveline clunk" issue on some later model C/K series light trucks, but could also be used in other similar splined-shaft applications.

Other than "highway speeds", driveline vibrations can also occur on acceleration (i.e., "driveline shudder"). Usually, this is due to the driveshaft angles (transmission to front part of the shaft, front d/shaft section to the rear section, rear section to the pinion shaft on the differential--or similar appropriate shafts on 4 wheel drive vehicles' front driveshafts). The reason that "typically ride height, as used" is important as it can change the interface of the "pinion angle" (the angle the differential pinion shaft makes with the horizontal, which is a "welded-in" angle, usually, as it relates to the basic position of the rear axle housing on the rear suspension springs/control arms/spring saddles on leaf spring rear suspensions). Each one of these joints has a "desired arc" they are designed to operate within, with reasonable smoothness, so when those joint angle tolerances are out of their normal range of movement, or a "self-damping" orientation might decrease, vibrations/resonances/roughness/shudder can happen.

Typically, GM has tended to favor multi-piece driveshafts on its longer wheelbase vehicles, also being one of the first USA manufacturers to use the "double center joint" interface between the front and rear driveshafts for enhanced smoothness. Ford and Chrysler typically made out just as well with single piece driveshafts in similar longer wheelbase vehicles. Probably a matter of design and engineering preferences?

On the last gen F-body Camaro/Firebird V-6 models, they had a two-piece driveshaft where as the V-8s used a one piece shaft. The two-piece V-6 shaft was unique as the center bearing was really a front wheel drive CV joint, rather than a typical universal joint or a double-joint setup. From GM, it's very expensive to purchase the total shaft assembly, but I suspect the joint could be rebuilt by a competet front driveaxle repair shop. I suspect they might have been chasing some driveline harmonics with the 3800 V-6 or they would not have gone to the added expense. The center CV joint would also act as a "damper" of sorts plus the shorter shaft sections would also tend to have a higher-resonant-frequency situation than a longer shaft would. As I recall, it also came with the carrier bearing mechanism "assembled" to the shaft.

Many driveshaft orientations. What was used where most probably had something to do with the design orientations and theories of the Chief Engineer in charge at the time of design, yet the final production items would also need to be tempered by other factors such as item cost, production complexity, "frame" issues relating to body structure/design, prior warranty costs, plus demographics and vehicle retail pricing, and customer satisfaction issues. A multi-faceted situation, to say the least!

Hope this might help 'splain some things. . .

The "sweet spot" can relate to many things, as mentioned. Other than engine/drivetrain issues, it can also relate to a particular speed range where the suspension "feels right" (i.e., road irregularities seem to not bother the ride quite as much as the shock absorbers are more in their "firm mode" of damping rather than smoooooooth and floaty) for a particular road surface and condition and relative straightness. This sweet spot can also change with just a 5mpg greater speed too! Below the "spot", the car can feel "bored, in the "spot, it is "having fun", but above the "spot", it becomes less fun and takes more input to drive. Many luxury cars of the '60s would criuse at 75-90mph "all day long", but if you went higher than 90mph, the suspension needed to be firmer and fuel economy further decreased. And, hopefully, if you ran that fast back then, you had close to 30-32psi (cold ambient temps) in the tires!!!

It's all in how the total situation comes together to make driving fun for the vehicle and the driver. Some of these things can be determined by mathematical formulae, others come from "educated feel" (which can come from experience). In the car hobby, there are times when it's appropriate to "flog the machine" (i.e., vintage racing on a sanctioned race track), but the typical orientation that many of us will fall into is more of the "enjoyment" side of things. What is "good" for one vehicle might not be "good" for another vehicle--depending on many factors, most of which we've discussed.

Enjoy!

NTX5467

[55PackardGuy]

Wow, thanks for opening the floodgates NTX! Truly a wealth of information.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Probably a matter of design and engineering preferences?</div></div>

I have heard but am not sure that the reason GM had an engineering preference for split driveshafts in their big cars was to lower the ride height and still maintain appropriate driveshaft angle at speed (and a reasonably small floor "hump"). The old '65 Electra was a real "slider" sitting right down on the ground. A great look, but it meant that the driveshaft had to be extremely low slung as well. I imagine the driveshaft angle at the rear u-joint (pinion angle as you noted) was the major benefit of the split shaft. As you know, at speed the pressure on this joint increases as the torque on the rear axel makes the whole axle assembly start to "tilt." This is usually where that irritating "roaring" noise comes from at high sustained speeds. No amount of driveshaft balancing can eliminate the noise, as it's really a normal u-joint noise--the greater angle that the u-joint is forced to contend with, the more noise it makes.

The split driveshaft allowed the assembly to be "hung" below the car, rather than be set at a continuous angle from transmission yoke to rear joint/differential as a one-piece shaft must be. This created a straighter shot to the differential while still giving adequate floor clearance. Ingenious system, but the "CV" joints in the center took quite a skilled mechanic to fix. I only watched the process of rebuilding these, and would never attempt it after seeing how much there is to it. I bet the famous Buick "torque tube" was used in the early days for much the same reason as the split shafts of later years.

TIRE PRESSURE and the whole discussion on tire roundness/balance and how it affects performance was very valuable. I assure you, with over two tons of metal at 80-90 mph, I did pay attention to tire pressure, generally going with the limit on the tire which in those days on the 4-ply bias tire was usually 35 psi. When running an older, heavy car at continuous highway speed even on today's rubber, tire pressure is critical--much more important than what's going on under the hood. If the engine dies, you just slow down and stop; if a tire goes, you stop in interesting ways!

I can really use your tips on driveline balancing with the Camaro, I think. You mentioned low-speed driveline "shudder" and this is also happening with the car. I don't feel it, but I hear it often when accelerating moderately at low speeds. I don't hear it from the driveline, though, but it makes the plastic in the dash somewhere give a very distinctive vibration! I wonder if this is also what's happening on a larger scale at 70 mph? If so, I'm getting suspicious that it's in the transmission yoke, because the vibration is coming out in the front part of the interior. It's just a guess though, as driveline noise "travels" so well and sometimes comes out in odd places far from the source.

"Sorting out" a car's driveline and suspension is so much fun and a neglected part of the hobby, I think. You're doing some of the same things as race mechanics--finding tricks that make a car with a wider, faster "sweet spot," better handling, and better performance at high speeds regardless of engine power. You never get to use all that horsepower unless you get into tuning more than the engine.

Thanks again for all the information.

[NTX5467]

Thanks for the comments and kind words.

On your Camaro, it most probably has a "torque arm" that goes from the transmission rear mounting area and is bolted onto the rear axle. As I recall, it has something to do with "locating" the rear axle. At the front area, it has some sort of rubber mounting that it rides in (the aftermarket makes a polyurethane version, which can locate it more accurately but could also allow greater noise transmission).

The preference for two-piece driveshafts also carries over into the light duty trucks. When they first tried to get away from them with the initial 1973 models, they ended up going back to the two-piece shafts. The later tried to move toward one-piece shafts (aluminum/composit construction) on some of the more late model C/K trucks, but still had vibration issues so the "fix" was a two-piece shaft assembly--again.

The driveline shudder issues were usually on the more late model C/K trucks. Some vehicles barely did it while others were worse. Didn't seem to be a really clear-cut situation it happened under. Many of the service manuals of prior times (i.e., 1966 MOTOR Repair Manual) were very specific on how to shim the center carrier bearing up or down to get rid of shudder/vibration at various speed/load combinations. With all of the manufacturing tolerances stacking up on some vehicles, it could be really tough to get things as they should be.

Those '65 and '66 full size Buicks were some great looking cars, with that customized lowered look (that comes in and out of vogue with time) "from the factory". It always looked to me like you had to look "at your knees" to see the speedometer, but everything looked so neat you didn't really worry about that. The lower beltline really openned up the vision for the passengers too. Definitely a big change from the '63s and '64s which evolved into the very well styled '67s and '68s.

On the issue of "u-joints". I'd always preferred the "greaseable" joints until my machine shop operative (and drag racer) pointed out that the drilled grease channels in the joint casting could weaken it and cause it to fail in high horsepower drag race situations. Of course, some of the aftermarket "drag racing" brands had "high strength" greaseable joints (with the definition of "high strength" not really defined as such). He noted that in some cases, as some OEM applications were doing, the solid joint would be the strongest. With respect to "damping mass", such a solid joint might also help with driveline resonant vibrations too--just a thought on why the OEMs would spend more money for a solid joint that most probably cost more to buy (when there were no real durability issues at hand). Upgrading the "factory pack" lube on these solid joints could aid long-term durability too, which I suspect happened too.

In the case of the two-piece shafts, the front section would (of course) remain stationary as the rear section went up and down. This could let the front section of the drive shaft hump be more tightly designed, but with the rear section needing more area, a crafty design would put that extra floorpan height basically under the rear seat area (and hidden). Also, with the Buick orientation of moving the engine forward in relation to the firewall/floorpan area, it made for a smaller total "hump" in the front section too (and a perceived more spacious interior due to that fact)--it's kind of interesting that lowering and decreasing the radius of the front floor hump could make so much visual difference in the feel of size and openness of the front seat area.

I never have really researched to see how Ford and Chrysler got away with using a one-piece drive shaft in the generally same wheelbase length vehicles as GM had (that used a two-piece shaft) and had no known driveline vibration/noise issues (as a general rule). It could have had to do with how the body overhung the frame (as mentioned) and it could have also been due to the use of the X-style of frame (which is generally where the carrier bearing mounted back then). Of course, with a little planning in the design end of things, it could have been (which is highly unlikely, by observation) that the front driveshaft sections were all the same and the rear section made up the difference in wheelbase lengths--which might lower total vehicle costs. It might also be a lost cause to find out the real "why" of the two-piece shaft, at this time, as those that might have known or have been involved might not still be with us today. Obviously a multi-faceted situation with many interacting issues and engineering/design orientations!

Enjoy!

NTX5467

[55PackardGuy]

Had no idea that GM pickups used split driveshafts, having only been "intimately familiar" with a '74 Chevy 3/4 ton that had a one-piece shaft.

Regarding the "slider" Buicks of '65 and '66, The '65 Electra accentuated that lowrider look with the long straight ribbed strip that ran along the sides not far above the rocker panels. It even flowed through the fender skirts. Years after I no longer had the car, I learned this "styling cue" was a mock running board!

It's fascinating to see all the borrowed styling elements--sometimes automotive and often aircraft-inspired--that were used in many vehicles. Another interesting one is the distinctive clamshell marker lights in first generation Rivieras--these mimicked old-style grillework from the LaSalle. Why the LaSalle? More trivia, the Riviera was originally slated to be a re-birth of the LaSalle nameplate and a Cadillac product! Sure glad Buick got the nod on the Riv so it had some performance orientation rather than a straight "personal luxury" motif! But the inclusion of the original design element gave the '63-'65 Riv a very distinctive styling feature. By '65, of course, they tucked the headlights under there.

I think I'll start with the "torque arm" in my Camaro driveline tune-up. Sometime next spring... Your comments have been duly copied to a Word document for future reference!

[old-tank]

A couple of other considerations for cruising speed are cooling and carburation. Most of our older cars will run hotter as speed increases, so there are times that sustained high speed driving is not possible or advisable. Also there is a speed on all carbureted cars where an enriched power circuit comes into play and fuel ecomony drops like a rock.

On my 55's that speed is 80-85mph...on my 51 Ford F-1 it is 60mph! This cooling and carburetion problem is probably related since extra fuel produces more heat. Not much fun to watch one gauge rise while another drops...

Willie

[Guest imported_Thriller]

Interesting discussion and a lot of learning happening at this end. Recently I had driveline work done on my '62 Special. The symptom was a clunk...like a U-joint, but not when shifting into gear...sometimes it happened when in gear from a stop (i.e. stop sign) or when shifting from 1st to 2nd.

As it turned out, the hanger (carrier?) bearing was the culprit...the rubber had been destroyed and the bearing was bouncing around. It was sent out to be re-vulcanized (and I'm told a very nice job was done). At the same time, they balanced the driveshaft and replaced the U-joints. This was done late in the season, but after that repair, shifts were very solid...what a huge difference in feel, from before the clunking started.

[NTX5467]

Most of the "power circuits" were activated by manifold vacuum dropping past a certain level (which relates to "load" on the engine rather than rpm). With respect to "road speed", this can also relate to vehicle aerodynamics and tire rolling resistance AND rear axle/tire diameter interfaces. And don't forget that more powerful engines can "loaf" at higher vacuum levels where smaller or less powerful engines will be more "strained" at the same road speed.

In the more modern automotive repair literature, the "power valve" is called just that (as it enriches the fuel/air mixture below certain manifold vacuum levels for additional power, with less fuel economy in the mix too), but in some of the earlier literature (prior to the middle 1960s), it was also called an "Economizer Valve" (being that when it was closed, it helped fuel economy by not adding any extra fuel).

Before we had metering rod carburetors, all carburetors were "fixed jet" and it was a technical advance when they could have an auxiliary valve to add extra fuel into the fuel/air mix under conditions where it would be beneficial to do so, but lean things back out when economy was needed--without the driver having to do it. This, generally, let the main system be jetted leaner for better economy. Kind of like the "advance" that varying the spark advance in relation to manifold vacuum (via the "vacuum advance") on the ignition distributor (over what the springs/weights already did--which was another "advance").

Many times, the "high speed overheat" issue can be related to water pump impeller speed being too high and/or undercapacity radiators and/or insufficient air flow through said radiator at those higher road speeds. Lots of variable issues relating to vehicle design and engineering for each respective vehicle/engine combination. Might even be a "retarded" spark timing issue or an "over-advanced" spark timing issue--at that particular rpm and load situation. Sometimes it's best to drive slower than when those issues become operative!

Enjoy!

NTX5467

[55PackardGuy]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Sometimes it's best to drive slower</div></div>

You said a mouthful there. Especially on vintage cars with low gearing and no overdrive, as little as 5 mph can make the difference between a nice ride and a fried ride over distance. With some of the later "turnpike cruisers" a little experimentation can yield where best smoothness and fuel economy live. Sometimes, if you want to cruise at faster speeds, you find that you have to increase speed past a certain midrange point before the car reaches a higher speed it "likes."

I wasn't familiar with the power valve issue at cruise--I always thought the valve opened only under acceleration. As for driving for economy with a 4-barrel, I like mechanical secondaries because you can usually feel the extra spring pressure in the pedal when you reach wide-open primaries. The vacuum secondaries can be a pain, opening gradually at speed and engaging those back barrels when you don't want them--and sometimes sticking! Never liked those gadgets. They seem like just a way to "enable" poor driver habits by limiting lead-foot "bog."

[NTX5467]

I concur about the feel of knowing you're "in the secondaries", but there are different "styles" of mechanical secondaries. The more common one many know on the Holley 4bbls, which are straight mechanical in nature (some Chrysler-spec OEM AFBs were the same way whereas the GM-spec OEMs and the current Federal-Mogul AFBs have a counterweighted air valve above the secondary throttle blades) and then the mechanical secondaries on the Carter AVS (Edlebrock "Thunder AVS"), Carter ThermoQuad, and Rochester QuadraJet (the later model spreadbore). The secondaries are still straight mechanically actuated, but the air flow is modulated/controlled by the air valve flap over the secondary throttle bores, which also move a pair of metering rods on the TQ and QJ to also control the air/fuel mixture in the secondaries. Not quite as involved as this might indicate, as there is also a mechanical (adjustable) spring pressure on the air valve that must be overcome as the valve opens for additional air flow (just enough, but not too much).

The vacuum secondaries on the Holleys are also tuneable. Holley has a kit of springs (color coded) to vary at what point they let the secondaries open and also how quick they open. It can take some road time and is a little more involved than changing the spring preload on the QJet or TQ or AVS, but not nearly as involved as grinding the counterweights on the air valves in the AFBs.

Key thing is to open these air valves enough that the engine is getting all of the additional air it needs under the particular power condition, but also not give it so much that it bogs.

On my '67 Chrysler 383 4bbl (OEM AFB, back then), it's a smaller 4bbl of about 525cfm. I could floor it and open all 4 bbls from idle and it would not bog at all--just move. When I went in and smoothed the throttle bores and venturis with sand paper (to get rid of the casting flash and "gasket match" them), then I'd get just a hair of a hesitation when I did that, but only if I went all the way open from idle. Rolling it out a little and then using that last 10 degrees of throttle openning worked well (after the clean-up).

I've heard of people having vac secondary Holleys that would open the secondaries under part throttle conditions (usually under high load in a towing situation with a larger V-8 and deep gears in a 1-ton chassis truck). In these cases, it was not openning as they normally would, but either "open" or "closed" with similar power/fuel economy relationships. To me, that would be a case where the secondary spring would need a change toward a stiffer one. Usually, you end up changing the spring to get the secondaries to open sooner on a street car and sometimes, as they are "as demanded by air flow bias"-controlled, if the engine really does not need the added air flow, they don't open at WOT.

In driving, the vac secondary Holley feels like a two barrel in throttle pedal feel, or in more recent times, a fuel injected vehicle. When GM went to TBI on their light trucks in 1987, there were complaints from the 454 owners regarding top end power (the trucks also had a single exhaust rather than a dual exhaust of prior years). The owners expected to get that "4bbl rush" when they were crusing at 75% of throttle and needed that last little bit of power (and the "4bbl feel") . . . and didn't get it. The fact that they didn't have a 4bbl any more didn't really sink in, it seems.

There were enough complaints about the different throttle pedal feel that GM put out a service bulletin. It stated that with a TBI set-up, 75% of throttle resulted in 90% of max air flow into the motor. Therefore, when they used to be right at the edge of getting into the secondaries, they were already pretty near where they'd be "in the secondaries" if it still had a 4bbl on the engine. So, there needed to be some adjustment on the part of the user in this situation. It could also have been that they were so impressed with the added driveability and lower rpm power with the TBI setup, they didn't really know just how much power they were actually using (until they went for more and it wasn't there).

Funny thing was that people raved about how much better those TBI pickups ran compared to the '86 carbureted trucks. Then, at the first oil change, there were complaints about "poor fuel economy"--but that's another story.

Enjoy!

NTX5467

[55PackardGuy]

That rebirth of the 454 didn't last very long, and maybe the TBI had something to do with it. I wonder whether anyone will have the guts to re-introduce a big-block pickup. Many people get scared away from them with thoughts of poor fuel economy, but as owners of vintage big blocks know, they can often provide better fuel economy than their small-block cousins, especially in heavy vehicles. More cubic inches does not equal less fuel economy, if the larger engine is designed for thermal and volumetric efficiency. (IMO the 454 doesn't qualify for this distinction, though.)

I had an '84 Mercury Capri RS with the 302 V8 and Holley 4-barrel with vacuum secondaries. The only mod I did to the carb was to take out the "check-valve" ball. Removing it was a simple matter of taking off the top of the carb and popping the little metal ball out of the vacuum circuit. That increased the speed of the secondary opening just enough to add a little extra zip. I read about it in Car Craft or somewhere and tried it just for fun. Never messed with the spring at all. Sure beats buying computer chips! That car was one of the last to pass emissions without electronic engine control.

Talk about an efficient V8! With the 5-speed overdrive, it made high-20's regularly in freeway cruising, and in particularly good conditions I topped 30 mpg several times on trips. I still say fuel injection is not the last word in fuel economy. It generally gives more consistent mpg, but often seems to come up short on the ultimate highway economy of a good carb setup. I think a carb can provide closer to ideal fuel atomization and mixture when it's working right. Problem is, keeping it working right takes a little tlc. But clogged or bad injectors can waste a lot of fuel too, and they seem to malfunction quite readily.

[Guest imported_Thriller]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I wonder whether anyone will have the guts to re-introduce a big-block pickup. </div></div>

I guess that depends what you mean...the GM 2500HD is available with an 8 liter (I forget exactly...it might be 8.1 or something like that) engine (about 488 ci). Pig on fuel though.

Then again, the 5.3l Vortec engine gets good power (now 300 hp and 447 ft-lb)...and they are putting the DoD into cars

[55PackardGuy]

I guess I was thinking in terms of a "light duty" truck like a 1/2 or 3/4 ton. I didn't know what models they started using the big block V8 engines. Is the 2500 a "1-ton" item? I think the "last hurrah" for a big-block V8 in a run-of-the-mill pickup was the 454 "SS" mentioned earlier. The Ford V10 might qualify as a bb, although really a "stretched" small-block. I think the Dodge V10 has gone the way of the dinosaur, and that too was more of a long block than a big block.

I think you said it all about the power they're getting from small-block V8s now. Probably hard to justify the weight and cost of a bb, let alone the bad PR.

So what's a safe cruising speed in a 300 hp pickup?

[Guest imported_Thriller]

Well, the 2500 used to be the 3/4 ton designation, but the capacity is well beyond that (seems to me it is over 3000 lb payload). As for safe cruising speed, mine was fine at 75 on Minnesota Interstate (with the Duramax).

[NTX5467]

Back in the early days of catalytic converters, the GVW "break" for having or not having the converter was 6001 lbs (the base GVW was about 5000lbs back then so if you ordered heavy duty rear springs, it meant it was more for "work" than "play" and it did not get the converter or related hardware). In later years, the GVW break was raised to 8600lbs as it seemed that almost everybody was getting the 6001lbs GVW 1/2 tons (later called HD 1/2 tons or "Big Ten" in Chevy models).

Just like we had two 1/2 ton C/K chassis truck designations (via optional equipment), we also ended up with TWO 3/4 ton C/K trucks by GVW ratings.

The base 3/4 ton C/K truck had a GVW of about 7200lbs. Where the 1/2 ton 2wd trucks had 5 lug wheels, the base 3/4 ton had 6 lug wheels and the HD3/4 ton had 8 lug wheels, bigger brakes, heavier duty rear axles, etc. In some circles, if you had a LD3/4 ton, it was a "pretend" truck and the HD3/4 ton was the real deal workhorse. In more recent times, the 3/4 ton trucks had some items specific to them, regardless of GVW ratings.

For many people, as the thresholds of performance have been raised, the HD3/4 ton has probably replaced their prior 1-tons as the capabilities of 1-tons have increased so greatly in more recent years.

Also, 8600GVW trucks are not required to post EPA fuel economy numbers.

In some situations, a current C/K 1500 4-door short box pickup has tended to replace the station wagons of old, as current Suburbans have also tended to do. Plus . . . RWD, V-8, and "reasonable" highway fuel economy (when compared to the earlier station wagons). Sure, the non-diesels will never get 30mpg on the highway at 70mph, but they also fit a particular need for a particular customer base that places size, comfort, towing/hauling performance, and utility over ultimate fuel economy -- everything's got a price attached to it somehow, just depends upon which account you want to put it in.

Enjoy!

NTX5467

[Philippe Racicot]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">

Those '65 and '66 full size Buicks were some great looking cars, with that customized lowered look (that comes in and out of vogue with time) "from the factory". It always looked to me like you had to look "at your knees" to see the speedometer, but everything looked so neat you didn't really worry about that. The lower beltline really openned up the vision for the passengers too. Definitely a big change from the '63s and '64s which evolved into the very well styled '67s and '68s.

Enjoy!

NTX5467 </div></div>

The 65-68 B bodies are my favourites, they had very nice rooflines on the 65-66 two doors as well as the 67-68 4 door hardtops. I really like the W ends on the 65-68 Buicks too. You are right about the 1965 Buick dash, the instruments were located very low (and the wiper switch too!). Even the flasher and tilt levers had to be mounted at angle so they wouldn't block the view to the speedometer... But I like how it looks and it's very easy to work on compared to most other 60's dashes. The 66-67 dash was completely redesigned and the speedometer was relocated higher.

1965 speedo, wiper switch and safe cruising...!

About the two piece driveshafts (and location of the engine), they made a big difference in interior space. The 1971-76 cars had a single piece driveshaft and their transmission tunnel was much bigger.

[55PackardGuy]

That blue dash is such a familiar sight! I had forgotten about that funny wiper switch down there in the corner, with the push-button for the washers. I never had a problem with the low-set gauges, because they were appropriate for the driver position, which was even lower! That "on-the-ground" feel was gone in our '69 Electra. It was a pleasant, comfortable car but never gave you that low-rider sensation like the '65.

It appears your "safe cruising speed" is a conservative 65 mph on the speed alert setting. However, the warning beeper must have been wailing for some time at the indicated 120!

[Philippe Racicot]

Guy,

There is no speed alert on my car, the needle is for the <span style="font-style: italic">Electro Cruise</span> (Buick's 1963-67 cruise control). You set it to the desired speed between 30 and 90 MPH by turning the knob (just like in cars with speed alert), push on it until the "CRUISE" light comes on (hard to see on this picture - above the 60MPH) and the car goes to the set speed. Once the cruise is locked, you can change the set speed simply by setting the pointer to another speed. You can also accelerate (quite fast!) from a stop to the set speed without touching to the gas pedal!

[NTX5467]

Some neat pics!

Before we got "pushbutton" cruise controls (on the turn signal lever) or buttons on the steering wheel, the Dana/Perfect Circle style of cruise controls had some sort of variable setting either in the speedometer head (GM) or on the instrument panel (Chrysler) where you turned a knob or dial to "a value" where you wanted the cruise control to engage. Once you activated and engaged the cruise control, you could vary the speed just by turning the knob up or down, similar to how you can "Accel" or "Coast" with current systems--all without using the accelerator pedal.

Seems like Chrysler went to their "modern" turn signal level cruise control in '68 and Ford started using steering wheel pushbuttons in that year also. Both had a "Resume" feature too and continued the orientation that once engaged (usually above about 30mph), you could vary the speed up and down without using the accelerator pedal. Ford had a vacuum servo that worked the throttle (similar in concept to what GM later used) whereas Chrysler used a one-piece mechanism with a stepper motor and a "lost motion link" on the carb linkage.

A good while back, a friend bought some obsolete parts from a Chevy dealer. In the "stash" was a GM Factory-Authorized accessory cruise setup for a '66 Impala-type car. It mounted the servo on the core support and used a long linkage that ran to the carburetor's throttle level. Seems that somebody has robbed the interior controls from it a long time ago, but the instruction sheets were still there.

Enjoy!

NTX5467

[Philippe Racicot]

These are pictures of the Perfect Circle unit for an Oldsmobile. Cadillacs had similar ones also made by Perfect Circle. Both had a rotary dial for speed setting and speed control unit mounted under the hood with speedo cables that enters in it like they did in the later transducer type cruise controls. Buick was the only division to use the Electro-Cruise which was a completely completely different system (I heard that some Pontiacs had it in 1964 but I have never seen one). Unlike the other systems used by other divisions, Buick's Electro-Cruise was the only one to be regulated by the speedometer itself. Unlike the Perfect Circle unit, it used a vacuum power unit similar to the later transducer type cruise controls but the amount of vacuum was regulated inside the power unit (by electrical current applied to a solenoid) instead of being mechanically regulated by the transducer.

[Buicks Rule]

66 T-birds had the cruise control on steering wheel hub, along with resume and I believe coast. I recall that touching one of the steering wheel buttons would apply the brake. Special steering wheel only used with cruise.

[NTX5467]

All of these early cruise controls only controlled the throttle. If you turned the unit off, either with the steering wheel (on the Fords) buttons or by applying the foot brake, the cruise "cut out" and it might well feel like the brakes were being applied, somewhat, when it was just engine vacuum slowing the vehicle.

Enjoy!

NTX5467

[Philippe Racicot]

On many cruise controls with vacuum power units, disengaging the system with the on/off switch wouldn't remove the remaining vacuum from the power unit immediately. This is why there was a vacuum hose linked to the brake pedal switch that would remove the vacuum faster in a situation requiring quick braking or if the system would fail to turn off. This happened to me with a defective Cruise Master transducer, when I pressed lightly on the brake pedal to disengage it, it remained on and the car was accelerating to keep going to the set speed...

When I braked harder, the vacuum bleed on the brake pedal switch opened and the car slowed down. Then I just kept braking and turned off the ignition. After that, I removed the hose going to the transducer and was able to get back home safely!

[55PackardGuy]

As Red Green once said, cruise control is the option that allows you to fall asleep without slowing down!

[Philippe Racicot]

Is the Red Green show playing in the US??!

[Guest imported_Thriller]

This year is the last season for the Red Green show...sigh.

[55PackardGuy]

The Red Green show has been playing here in Minnesota for gosh, years and years--I believe every season has aired. We even won a public television pledge drive promotion and got ol' Red himself to come to town for the "Duct Tape Forever" movie opening. He gave autographs and introduced the show, which was a dang good movie. If you haven't gotten the book "Red Green Talks Cars (A Love Story)" you owe it to yourself as a serious collector to get it. Well-documented uses for old K-cars and "Why British Cars Are Crap" etc.

[Buicks Rule]

W,

I seem to recall seeing the brake pedal move on that 66 Bird in response to the steering wheel switch. Maybe it was just vacuum bounce or fading memory as it was many years ago. This would have been on a nearly new car.

[NTX5467]

Considering how Ford did some things back then, they might have had a vac actuator under the dash that would move the brake pedal just enough to turn the cruise "off", as if the driver had tapped the brake themself, but used their finger rather than their foot.

I remember them using a "chain" to run from the throttle's vac actuator under the hood to the carb linkage. In the earlier ones, it was "open" and could catch on some of the nearby engine parts and "hang" and "not release" when the unit was deactivated. The factory fix was a shield under the chain. I guess that if the cruise was set, the driver floored the throttle to pass, then backed off to resume normal cruising, the limp chain would catch on something on the intake manifold and act as if the cruise was set for a higher speed, but in reality, the vac actuator has extended to the non-working or "coast" dimension, further complicating the limp chain issue.

Chrysler had an integrated underhood unit on the '68 and up models, which used a cable with a "lost motion link" on the carb to allow the cruise to be set and the driver to override it without causing any linkage issues. I'm sure they had a spring-loaded actuator on the earlier units which used a solid linkage to accomplish the same thing.

Ford's "better idea" back then -- that little chain that could snag on an engine part.

Happy New Year, Y'all!

NTX5467

[Philippe Racicot]

GM also used a chain (a ball chain), but I never heard that the chain could cause problems since it was short. The pre-71 full size cars had their diaphragm located on the firewall and the ball chain went in a pulley, then on the accelerator linkage. Later models had their diaphragm mounted on the engine and the chain went to the carb. To avoid getting stuck somewhere, there was a piece of black hose over it (the same size as a vacuum hose).

These are pics of the Electro-Cruise power unit and chain on my 65 and 67. (You can click on the image to see the chains)

65 Wildcat

67 Riviera

The same system was used on all the 63-67 Buicks except for the few 66-67 LeSabres and Special/Skylarks with the 300 transmission and the unusual <span style="font-style: italic">Auto Cruise Control</span> (a hydraulic system controlled by a transmission that was specific to cars with the cruise control option)