425 engine upgrades

[Jesse]

OK... so it seems like there are some genuine Riviera enthusiasts on this board... i'm enjoying reading it.

What i'd like some advice/help with is ways (if any) to improve the performance on a 2bbl 425 engine in a '64. Maybe starting with the easiest/less expensive and going up.
I'm not looking to turn it into a 500hp+ muscle monster, but just some overall improvements.
I know my way around an engine but by my own admission am no grease monkey, so any and all help is truly appreciated!

[The Old Guy]

I don't think Buick ever built a 425 with a 2 BBL carb. Are you sure your engine is a 425??

[Jesse]

My bad, I typed in the wrong number, it does indeed have a 4 bbl carb.

[The Old Guy]

The obvious upgrades are :
2X4 intake that was available for that engine

a mild cam that has an increase in lift, but not too much duration . This will still get decent economy, and give a boost through the whole RPM range

a less restrictive exhaust system (not necessarily headers,) mandrel bent pipes, and some better flowing mufflers

[imported_Thriller]

Jesse,

Just curious about what you are looking for...with well over 300 hp and 465 ft-lb of torque from the factory, just keeping it in tune will be giving you a relatively powerful car.

I'm not expert, but I think The Old Guy gave you some good suggestions...flow is almost always a good thing.

[Jesse]

Well, like I said i'm not really looking for huge horsepower gains.
Just upgrades in relation to smoother performance, better breathing etc. I already have Flowmasters on there and am looking to change up the air filter to a K&N. I live in Miami so the heat here is an issue especially during summer so i'll end up putting an aluminum radiator on there too.

I figured that their were guys on this board with way more experience than me with these cars who might be able to help me with some general tune-up ideas.

[brh]

After being in a 64 "Cat" with a 401? and losing a bet that the car would not lay rubber for the entire intersection and beyond I gotta ask too what more do you want out of the Riv? Some things you may want to look into. Has the car been tuned down to run on regular fuel? Is the timing to specs and are your plugs correct? She should be burning prem$$$$. My little 300 will not tolerate anything less, I have the high perf engine. I would not go with a Aluminum radiator, just have more rows added to your existing one and make sure your thermostat is operating correctly (just personal preferance). Sounds like you have breathing covered. If you take the engine down having it "blueprinted" with also help it out. But what will always be an issue is she is a heavy car. My buddies cat would twist off univeral joints regularly and he was too cheap to buy new ones. A trip to the boneyard every 6 months. Just some thoughts.

[NTX5467]

I concur, you should not need an aluminum radiator for any reason. If what you have is already a 3-row core radiator, making sure the bottom section of the core is clean and free-flowing (as the bottom is where all of the sediments and such settle out and clog things up, while the upper cores still look good). Make sure you have a good fan shroud on the radiator too (something you'll have to configure/adapt/build if you go with an aluminum radiator). Also make sure the fan clutch is a thermostatic one rather than a "centrifugal" one (although the former was standard equipment when a fan clutch was an upgrade from a fixed fan, yet the thermostatic one is the better way to do it and should be available for later model Buicks with the same water pump bolt pattern for the clutch).

Once you have these bases covered, then make sure that there is sufficient baffling to make sure that all of the air coming past the grille goes through the radiator and (if equipped) a/c condensor rather than around it. A somewhat simple thing to do and still have everything look factory.

Key point, when everything is working properly (including having the correct ignition timing for the engine!), then your cooling system "heat" issues should be minimal. Just curious, why is the Miami heat worse than in Phoenix, for example (other than for humidity issues)? Just for insurance, if you spend a lot of time in slow-moving traffic in "the heat", then you might consider adding an electric "pusher" fan in front of the radiator. The radiator recore/check plus the other things I've mentioned should be a good deal less money than the aluminum radiator you mention.

If you're having ignition issues, then an upgrade to one of the electronic conversion kits would be a good idea. Either way, make sure the ignition timing is correct for the application and you have sufficient octane to let the engine run well (with the possibility of a hair of clatter at WOT--hair, period, not more). Retarded ignition timing can contribute to more heat in the coolant, which is why the mention of the engine being adjusted to better tolerate regular-grade (pump octane 89) fuel rather than the premium-grade 93 octane fuel. You might put some fuel system cleaner in it and drive it on the freeway until the tank is down to about 1/4 tank. The desired result would be to get any residual carbon deposits out of the combustion chamber and hopefully make it more tolerant of modern fuels as a result.

To me, the 2x4 setup would look good, but you can probably get similar performance with an aftermarket intake manifold for that motor (swap meet stuff) and then put a more modern-design carb on top of it. When properly calibrated, one of the newer "Carter" 4bbls would probably work as would one of the more generic, but for that era of engine Holley 4bbls. Check the Holley online catalog website for particular applications. Only thing is that these later model carbs would require an air cleaner with a larger mounting hole than what you have. Considering that the stock 4bbl was probably doing good to rate 450-500cfm (in those earlier days, they used "venturi area" rather than cfm flow rates), putting a 600cfm carb would probably help the upper rpm ranges (when the secondary openning is correctly calibrated). Generally, the aftermarket intake would flow a little better than the stock one did.

But, by the same token, when what you have is tuned to work its best, it might not lay as much rubber with modern radials as it would have with the skinnier tires that came on it, but if the tires don't spin, the car is moving forward as you move farther back into the seat padding.

Before doing any sort of engine mods, always get the original set-up "baselined" so you know when you make an improvement and how much better it might be. Therefore, go through the tune-up specs and make sure everything is where it needs to be. Get used to driving it too, even if it might now require super unleaded. I concur with The Old Guy's camshaft spec recommendations, but I believe that what's already in there is pretty good too. In a heavy car situation, you want torque rather than 5000rpm horsepower to get things moving and burn the tires.

I'm not sure what automatic trans might be in there, but if it's a 2-speed, then upgrading it to a THM400 would definitely make it "cook" from a dead stop. One of our chapter members had that done to his '62 LeSabre and he was totally surprised how much better it ran and acted than with the DynaFlow. Just something to think about, which could be an incognito upgrade when you get the correct shift quadrant "things" in there so it looks like it came that way.

But for now, getting your existing set-up tuned and baselined would be the first thing to do. Then you can do some searching for availability of other parts (cams as The Old Guy mentioned, for example, plus an aftermarket intake and carb, possibly).

Enjoy!D
NTX5467

[Jesse]

Thank you both guys - the info you posted is very useful and i'm sure i'll read it a few times.
I think for now i'll take the engine in and have it checked over. I just want to make sure it's currently at the performance level it needs to be.
With the breathing already dealt with, it's possible I might switch to a 4 bbl carb... but i'll take my time on that decision.
NTX - the heat issue in Miami is indeed the humidity. You HAVE to run AC, i'd say 75% of the year. Summer temps can hit 95 with very high humidity for weeks on end. My friend actually recommended a pusher fan too.

Once again, thanks for the help.

[NTX5467]

With the humidity issue, only "heat" will typically affect the cooling system rather than the combination of heat+relative humidity.

Where the humidity would come in is with the a/c itself and it's struggle to handle the humidity (i.e., dehumidification). The "extracted" heat will transfer to the a/c condenser, which will add heat loading to what the radiator sees . . . again, heat itself. IF the a/c is properly charged, you'd be surprised how much less it'll load the engine and work well rather than if it's in a partial charge or an overchaged state. Air flow over the condensor is a key issue, which is where the additional "pusher" fan can come in, especially in slow traffic with a tail wind or side wind.

Take care,
NTX5467

[Steve B]

Nailheads typically don't breath well. The 425 uses the same heads as the 364 and 401. This means more air is required through the same heads to support a larger displacement at the same RPM. Better breathing is always the point to address with these engines. The intake, heads, cam and exhaust are where the gains in this engine are found.

The stock intake is set for a small base 4 bbl carburetor (AFB, Rodchester). These are low cfm carburetors on a restrictive manifold. There are several after market 2x4 manifolds and a Buick 2x4s available. The Edelbrock b262 is best 2x4 to have, but they are hard to come by since they are not manufactured anymore (ebay prices over $500). The Buick 2x4 also provides better flow over the stock 2x4. These manifolds were made in limited quantities and are also hard to find and purchase. Offenhouser has a 2x4 manifold for this motor, but it is restrictive at the turns. There is a 2x4 under testing made by Eelco that is said to be similar to the B262, but the results are not in. The stock square bore manifold can be machined larger to accept a large base square bore 4 bbl (PAE Enterprises), and a Buick Quadrajet spread bore manifold was available in 66 on the 425. These manifolds will allow the use of larger flowing carburetors and improved manifold flow. This is a cheaper option to the 2x4 and will allow for improved flow and more common carburetors (Holley or Quadrojet). Don?t cap it off with a restrictive air cleaner set-up once you improve the flow through the intake and carburetor.

Heads flow can be improved once the intake manifold flow is increased. The most common thing to do is porting to improve head flow. Larger intake valves (1.94") can also be added, but require some un-shrouding in the chamber. Intake and exhaust port flow is improved through porting. Ported Nailheads can flow as well as a good set of street/strip ported 455 heads in the right hands (Gessler). Port matching the intake to the heads also provides some air flow improvement. Smoothing rough/sharp edges and un-shrouding the valves also improves flow and decreases detention.

After market cams can provide improvement in air flow, but can also be a major stumbling block. The cam need to be matched to the rest of the engine, compression, drive-train and weight of the car. The right cam can pick up HP, the wrong one can seriously compromise the combination and leave one scratching ones...... Cams with more duration and lift move more air at the cost of moving the power band up the RPM range. This can put you in a situation where part of the power range is beyond the upper air flow limits of the heads. This causes the engine to run out of air right where it starts to make power. Cams may also require transmission converter stall changes or rear gear changes to work well as part of a combination.

Moving more air in means moving more air out. A restrictive exhaust with other improvements will not net any gains and increase back pressure. Headers and shorty headers are available for the nailhead. 2.5" exhaust systems are available for most A-body applications and will handle up to 600 HP without any negligible effects. The guys running fast nailheads report lager primary tubes are better for HO nailheads. Available headers have 1 5/8" primaries and 2.5" collector. 1 3/4" or 1 7/8" primaries with a 3" or 3.5" collector would be better if you can find them. There were some sets like that made, but they are hard to come by.


HTH

[NTX5467]

A good explanation! I was thinking that I'd seen where somebody was doing a re-run of some Nailhead intake manifolds?

Balancing cylinder head flow with intake flow with "outflow" can be a task, sometimes. Once you know where the upper limits are (valve lift wise), then you can better choose the camshaft specs. Improving "low-lift" flow can work well in a stock-type engine, but in a higher horsepower drag race motor, the higher-lift air flow can be more important as valve lift is increased along with duration. In published flow bench tests, where the Chevy Vortec 350 cylinder heads have a big increase over their prior generations is in the low-lift flow. If you've got an application where cruise rpm is in the 2000rpm range (rather than the 3000rpm range), you've got to have a mild cam duration (i.e., shorter) to have good torque in the lower rpm ranges, so the additional low-lift flow can add "area under the curve" for airflow.

There is also a balancing point between port velocity and total air flow too. Smaller ports and valves might be bad for 6000rpm power, but they can also help with lower-rpm operation and torque. In later years, port shapes and short-side radii of the ports and how they might interface with valve guide intrusion have been areas of research, not to mention mixture swirl in the chamber. Up to a point, larger ports can help power across the board, but when things get too big then port velocity can suffer at lower rpm levels and so will power and throttle response, plus torque.

In engines with somewhat restrictive (seemingly by design) intake manifold and cylinder head port designs, cam event timing can be altered to affect some additional power. I recall the engine seminar at Flint, when it was mentioned how much extra power was gained with a little added exhaust duration to a particular GS engine . . . which would tend to indicate that the port was somewhat restrictive and needed the additional duration to effectively scavenge the exhaust gasses from the cylinder (for a more undiluted intake charge for the next revolution of things). This is one way that cam timing can somewhat compensate for these things, especially on the exhaust side of things.

I know that one of the time-honored modifications on the Y-block Ford V-8 was to put bigger valves in it and also clearance the side of the combustion chamber to not shroud the bigger valve too much. In the Chevy small block V-8s, while there were 1.72", 1.94", and 2.02" intakes for the same heads . . . depending upon if it was a truck or 327/250, car, or HP engine . . . all in the same combustion chamber. The dyno charts I found for 1970 engines did not really put more torque in the truck engines with the 1.72" intakes, but going from 1.72" to 1.94" in the 327 V-8s (plus a little bigger carb and dual exhaust) was worth the additional 50 horsepower. On the heads that came factory with the 2.02" intake valves, there was an additional radius cut on the combustion chamber wall by the large intake valve. NOW, the question might be if you had a set of 1.94" heads and put "undercut stem" valves in it, if it would end up flowing (in a pretty much stock or, say, 350/350 engine) as well as the 2.02" intakes would? In other words, there can be some other methods to get more flow on the intake side rather than just putting bigger-head valves in the chambers.

When the Nailheads and Y-blocks and other HP engines of the 1950s-1970s were designed, the ports were pretty much designed "by look" rather than with flow benches or ways to determine the quality of the actual air flow through the ports. There were probably some similations (when laminar flow was being considered, in the earlier times), but the whole air flow stuff was still in its (by comparison to current references) infancy. Stratified charge was a key thing back then, for example, which was more in the diesel side of things than in gasoline/spark-ignition engines of that timeframe.

I remember reading where when they finally flow-benched the Pontiac Ram Air IV heads, with their round ports, they didn't flow any better than earlier RA series heads. Yet when they came out, the round ports were supposed to be the best shapes for ports--in theory.

Further research revealed that most stock Pontiac cylinder heads didn't flow too well above about .455" lift, which is pretty much where their high perf cams for the general street motors were, but they had longer durations with that lower lift. Another consideration in camshaft specs is the lower lift and longer durations being easier on valve springs and components. Some of the drag racers I know of (from several years ago) tried some "killer" camshafts in their Chevy race motors, but they ran not a whole lot better than what they had previously, but they were going through valve springs much faster. Most went back to their earlier profiles and tweaked some more for the same results.

I would concur that the Nailhead QJet intake would be better than the earlier ones--especially in the carb availability areas. Just with the carb change alone, it would generate about an extra 200+ cfm flow, plus more accurate fuel metering in the cruise mode (when the jet/rod/spring metering items on the intake side are properly calibrated). The key would be if the manifold under the carb mounting flange was any better than the manifolds for the earlier engines with pads for the smaller flow carbs. David Vizard had a really good article in a recent Popular Hot Rodding magazine on intake manifold design.

In one respect, much of what it might take to get the best power/efficiency out of the Nailhead was done pretty much by "hit or miss" in the earlier times, when bigger was always better (typically). Perhaps some of the modern knowledge of port shapes/designs can be adapted to the earlier engines to better unlock what they were trying to do back then? Back when "shrouded intake valves" might have been used to induce swirl or turbulance into the incoming mixture, possibly (some of the stratified charge orientations)? Then add in some of the "active air" orientations of later 1980s NASCAR research? At this point in time, these things might be on the fringes as there are few new castings for those heads (I suspect) that could be sacrificed for such research and testing. Not to mention the affect of piston crown designs upon what ultimately happens in the combustion chamber.

But everything is a big balancing act to get things to act "right" in one rpm range and not adversely affect what might happen in other areas of the power curve (especially low rpm torque).

Just some thoughts,
NTX5467

[Steve B]

Little more information on the various head flows at lift here. There are some interesting comparisons to be made. Mr Magnotty told me my intake was not the restriction when he ported the heads for me that are in the chart. He flowed and worked my Q-jet intake, but it did not take much more then fine tuning. I think the square bore manifolds will flow the same as the Q-jet when they are opened up to fit the larger square bore carb. The plenum is also enlarged to meet the bores of the larger carbs when this is done. The stock square bore and the stock Q-jet are very similar in design other then the plenum size.