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safe redline for 401 nailhead with 115k miles


65wildcatconvt

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hello all- -30 below up in northwest wisconsin this morning so dreaming of summer. anyway, an old high school buddy of mine challenged me to a 1/4 mile race this coming summer on a deserted county road.

my car is a 65 wildcat convt with a 401 nailhead engine and the th400 tranny. the running gear has not been rebuilt or touched as far as i can tell. the car has 115k miles on it i think ha ha.

so i dont generally beat the car and i maintain it well, just curious what you guys would spin these motors up to with minimal chance of explosion? i love the nailhead engine but dont know much about it as we usually souped up chevelles and novas in high school 33 years ago.

i am thinking 4000 rpm max... and would you guys leave the colunm shifter in drive or shift manually?

car i am racing is a 69 buick lesabre 4 door i think with a 350 2 bbl carb so if i lose i will hang my head in shame.

i read an article on the net a while back saying the nailhead engines have a steel crank and rods if i remember correctly heard they are a tough motor, was at a car show once and a couple guys said they tried to kill a beater wildcat they had back in the 70s and they said the running gear would not die.

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Here's my story.....

I've had my 65 Electra with a 401 since 1973 and I'm on the third engine. The saga......

Bought it in 73 when a junior in HS. The engine blew on Rt 80 (1978) heading west through the Pa. mountains. Had about 135K on it at the time. The number 7 rod broke or came loose and took out a section of the cam. Lots of scrap metal in the oil pan when I took it apart.

Bought a 79 Buick Skyhawk till I could find another engine.

Found a replacement engine in 1980.

Had the car at a bodyshop in 1981 and the guy said it would not start when he tried to move it. I went over to get it started and noticed that it was backed into one of the stalls. So I was suspicious. I think they were out hot rodding it and guess what.....It had a broken #7 rod too and it took out a section of the cam. That engine had less than 100K on it. I was not a happy camper.

My old Buick sat in my garage till about 2002 when I acquired a 'new' 401 that had never been installed in a production car (that's another story). I started the long process of fixing and restoring my old car in 2003 or so and it is mostly done. I've got less than 2000 miles on her now.

If I really liked the car, I'd pay him $20, tell him he won, and live to drive the old nailhead another day.

Bill

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great story bill, ya i am 51 years old and i feel like throwing a rod every now and then esp when i am at work... believe me i love this old car and am not in a position to spend a lot of money on it right now, just very grateful i even have it.

i remember reading something about nailhead engines being used to start sr71 spy plane engines in the 60s i think

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SR-71 start carts used two "Buick Wildcats" connected to a common transfer case to start the jet turbines. Not so much the rpm's but the torque to hold the turbines at speed until they would ignite. Buick offered tachs in the mid 60's and if I'm correct, they redline out at 5,000. That's still a bunch of rpms for this engine. Nailheads ARE NOT Chevies, they don't rev up. You get your power from the low end torqe. Don't try to build them like a Chevy.

Ed

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I don't presently own either car, but I essentially have driven both back in the day. I owned a '65 Electra 225 with the 401 and my parents bought a new '69 LeSabre 4 door with a 350 back in 1969. The Electra would smoke the tires, but the LeSabre would just go.

I remember racing my then wife at a stoplight while I was driving my '63 Impala SS with a 327. She was in the deuce and a quarter and when the light turned green she floored it. The big beast roared, but just spun the tires while the little 327 Chevy just went. I think the comparison might go something like that. Not quite as dramatic as the weight difference between the Wildcat and LeSabre is not as great, but still the same outcome I think.

SO, I suppose it boils down to driving skills. If you can keep your foot out of it until you get going a bit, you stand a much better chance of winning that race. JMHO, but it was fun to remember...

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When I had my 66 Gran Sport ( w/ 4 speed) I kept going through water pumps. Finally one pump came with a warning tag not to run the engine over 35 MPH in first gear. I don't remember the RPM of 35 MPH in first, with the 3:42 rear. Maybe someone can help with that?

Also when I was driving Dads 65 Electra in my early years, I went through 3 sets of motor mounts. That engine however did round the clock twice without a rebuild or even a valve job.

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EACH GM engine brand had their own particular torque characteristics and endearing qualities. In the case of the larger Buick V-8s, it was "torque". Using torque correctly can trump "high rpm horsepower" as it gets you there before the other guy's horsepower at higher rpm can start to happen (with gearing being similar).

Each engine also has their own "critical rpm" regarding things coming apart, by design. I found a formula for that years ago, but don't remember plugging the Nailhead specs into it.

For a basically stock motor, I'd say 5K rpm would be a good place to limit things. Also remember that with a manual trans, or an automatic to a lesser extent, although the tach might indicate "5000", by the time the shift completes the rpm can be a bit higher.

Also, as the Chevy 327 story indicates, tire smoke might look and sound neat and powerful, but some Chrysler drag racing research (in the later '60s) indicated that the optimum tire slip under acceleration was 10%. Make a respectable noise, but also go forward, quickly. With torque motors, as Buick nailheads tended to be, have to have a little discretion off the line to optimize forward motion.

One thing I'd be concerned about is the timing chain and if it's been replaced. Plus that the engine had a fresh oil change and reasonably-fresh spark plugs and really good plug wires. These things would make it more fun and efficient to drive normally, too.

If the 350 is a 2bbl, it could well be the "small" 2bbl Rochester carb with the 1.44" throttle bores. They run well, too, but really need the additional air flow of a 4bbls' secondaries to have better power above about 3000rpm.

Might be best if y'all remain friends. If somebody needs a barn pulled down, then you'd get the call. If somebody needs more economical transportation, the LeSabre gets the call. I.E., no race.

NTX5467

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Well, I think your car should have the variable pitch converter. Assuming it does and its working properly, that's going to weigh in nicely in your favor. For extra insurance, an inexpensive and big-bang-for-buck addition is to have your distributor modified so you can run more initial advance. Tom Telesco (board name Telriv) can help you with that. Make sure your carburetor is well tuned as well as engine in general. Be sure to remove any unnecessary weight from the car before the race. Shift manually. You shouldn't need to go more than 4000 rpm to win. The low end torque of the nailhead and switch pitch will win the race assuming friend has a stock 350.

Often, driving skill is critical in these types of races. Do some solo test runs ahead of time to get a feel for how the car responds and hone your techniques.

Wouldn't hurt to do a compression test on your engine just to see what kind of shape the internals are in.

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thanks for replies everyone..

alright, when i purchased this car in 2012 it would barely pull itself up onto my trailer, but did not smoke or knock so i took a gamble. under the hood basically looked like it was 100% original as in everything neglected and not ran very often. i got it home, repaired some leaks, found 3 spark plugs finger tight, looked like original plug wires etc. anyway i got lucky and it runs strong and smooth with just basically a tune up. never got around to a compression check yet just because it runs so nice but its on the list.

i did some metal repair and now am prepping to paint the last 1/4 of the underneath of the car with rust bullet, as i did most of the undercarriage last winter. then changing the tranny fluid and filter as long as she is up on blocks. the tranny shifts decent and smooth, i have always been a big fan of th th400 as i had a big block 71 nova with th400 (homeade, car was originally a 6 banger with a powerglide) and a 69 chevelle with 396 chevy motor and th400 ( also homeade car originally 307 with powerglide or th350 cant remember) back in high school. i think there are 2 wires coming off the trans so may be switch pitch, it has some funky downshifting apparatus up on the carb that is not hooked up...

one of the reasons i was really attracted to this wildcat was: 401 big block from factory- somewhat high compression motor 10:1 or so i think, from the factory-cool- 4 bbl carb- factory th400- kind of a slight lumpy cam from factory- that is cool as heck ha ha. and burns rubber just halfway stabbing the throttle- cool!

so one of the first things i did- dual exhaust of course!

my goal is to keep working on the car in the winter, and always keep it drivable in the summer if possible

so i will race, just cause these are my old best friend hot rodding buddies, but will go half throttle starts and then somewhat hammer it down if i need to and im not going over 4 grand rpm even if i lose, i just love the sound of this motor!

was going to hold off on timing chain one more year but maybe if time permits should do it... what do you guys buy for timing chain sets??? steel gears? napa parts?

there are not a lot of motorheads around anymore so thanks for listening

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60flattop- you got me there!:D alright now only going 3750 rpm ha ha. believe me this is all in good fun with my excellent friends and if no race happens they are cool with that. truth is i love to hear the pipes on the car so i rev her out a little once in a while...just cant help it

johnd1956- or anyone,, my car has a approx 10" long thick steel bar bolted to the block lower driver side front and looks like it is supposed to bolt to the frame??? it looks original and factory made but is hanging there, is this some kind of torque bar or something? did gm ever do anything like that?

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The local Buick Performance Group used to rent out Texas Motor Speedway once a year for their annual Buick Race Day. It was bracket racing so it didn't really matter how fast you were as long as you were consistent. I raced my 1966 Wildcat a few years. It was completely stock, including bias ply tires. I would drive around the water used to wet the tires for initial burnouts so that I wouldn't spin the tires. I left it in Drive the entire time and would floor it when the light turned green, as quickly as I could without spinning he tires. Once I got passed the point of spinning the tires, I held it down to the floor the entire time and let the TH400 transmission shift by itself. I ran 16.50 in the 1/4. It was very consistent running it that way, and I won 1st in my bracket the first year and second in my bracket the second year (I ran a bit faster than 16.50 and broke out on the final race). Anyway, don't be afraid to just leave it in Drive and floor it. It can handle it.

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txbuicks-my same friends and i moved to texas in 1983 as there was no work in nw wisconsin, we drove down a 72 chevelle i had, we finished putting the motor in it the night before we left. 1500 mile trip, no shift linkage, had to leave it in drive all the time ha ha shifted it under the car right on the tranny if you needed to. im still working for the same company i found a job with down there 33 years ago up north in my home state... great memories of texas, what a great state.

have a good weekend everyone

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As for timing chain sets, the "classic" deal is just the normal auto supply full-metal gearset, using the chain and the cam sprocket only. When I put a timing chain in my '77 Camaro at 92K, the factory chain was still pretty decent, but some Buicks (I've known about, even back then) usually needing something by 80K. That's about when most of the factory sprockets would lose some of their plastic/nylon teeth. I put a Cloyes Plus Timing Set in the Camaro. Something of a hybrid between a "true roller" timing chain and a normal chain. I put it in at 92K (along with a cam upgrade) and it was still in the motor when I swapped a 355 in its place, about 625K miles later. The 355 has one in it, too. Has a little "bicycle chain noise" at idle, but I know that sound and that's fine . . . just as some like the sound of solid lifters at idle.

KEY thing would be to get at least OEM quality parts. Considering what can happen when a chain/cam sprocket can fail, it's cheap insurance. I don't know that you need to get one of the timing sets where you can install it slightly retarded or advanced, just put it in "straight up" normal. I also made sure to pour some motor oil over the new chain when I put it in, plus some cam assembly lube on the teeth and on the backside of the cam sprocket. If you get one of the roller chain style sets, you'll need to change BOTH the cam sprocket and the crankshaft sprocket. If you do a normal-style chain, you can do what I mentioned above, just change the cam sprocket and the chain.

The THM400 is a really good automatic transmission. They have an electric-triggered WOT downshift switch, either on the carb or under the instrument panel (above the accel pedal). Two wires would be the kickdown and the switch pitch controls, I suspect. Back then, I believe that most of the THM400s would shift in the 4400-4600rpm range at WOT, in Drive. Maybe 4800-5000rpm in some "performance" applications?

Keep us posted on your progress.

Enjoy!

NTX5467

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Around 1971 or '72 my sisters Chevy Caprice was recalled for bad motor mounts. The fix was a steel cable attached to the motor mount and wrapped around the bracket for the A frame. The 65 Electra we had was not recalled before my father sold it, but I have seen that "fix" in at least one other 65 Electra.

I doubt that steel bar you mention was attached directly to the frame or there would be a lot of engine vibration transferred through the vehicle. But that does not mean it could not be attached to the frame by a cable or a piece of chain. In the case of the Electra, the first time the mounts broke we kept hearing a loud scraping sound when accelerating aggressively. We found out the hard way that that noise was the fan hitting the fan shroud while the engine flipped on its right side in it's cradle. The other two times as soon as we heard that noise we knew what was up and backed off the gas. My brother was actually driving when the first set broke. As I recall, he was driving dad home from work and he said listen to this. The light turned green, he stabbed the gas, the engine flipped dragging the accelerator to WOT, and all my brother could think of was two feet on the brake pedal while it was still burning rubber and pushing forward with locked front tires. Dad was flipping out but managed to reach over and turn off the ignition before anyone got hurt. Glad I missed that ride.

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thanks everyone for the great info

johnd- i have been wondering what that steel bar was for, for 3 years, i always just left it there in case i ever ran into someone that knew what it was for. no matter what way you moved it, it would not line up to bolt to anythlng,but makes perfect sense if there was a cable or short piece of chain on the end of it...

sure is strange where a thread can take you .

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Back in the mid 1990's I was painting the rearend housing for my Riviera on a Saturday night and listening to a '50's Rock radio station. I couple of guys from a town north of me called in a request. The DJ asked a few questions and it turned out they were in the garage working on a 1966 Chevelle.

I called in a request a little later and he asked what I was up to. I told him "Painting the rearend of my '64 Riviera." The DJ said "Wow! That's detail. are you going to a show?"

I said "Nah, I just wanted it to look nice 'cause its all the Chevelle guys will see."

Bernie

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alright, high of 2 below today but I got a chance to look at that metal bracket after sawing some firewood.

turns out it goes from the front of the motor mount driver side to the bottom of the power steering pump.

in my defense before you guys laugh, it must be noted the bracket was bolted on backwards to the motor mount and facing down to the ground by someone in the distant past and also I have not seen a car like this in person since 1979.

first time I remember seeing a wildcat I had just started a full time job pumping gas at a full service station. I was 15 and in high school, did not know squat about cars. this guy pulls up in this car and says "fill it up" so I say yes sir and proceed to look for the gas door or cap. checked both sides of car... pulled on license plate thinking "its gotta be back here" I think I kinda bent the poor guys license plate... looked on the sides of the car again and scratched my head. finally looked under the car and saw where the filler pipe went up to... pulled on the buick emblem, thought hey this is kinda cool ha ha so ya I can be kinda thick skulled.

so I took the bracket off the motor mount today and tried flipping it around and put it more towards the top of the motor and then saw that it goes from motor mount to power steering pump, at least I hope that's right

this car has been kind of weird and I think it has some stories to tell as the grill was in upside down,( it took me a while to figure that out), half the exhaust manifold bolts were loose, it has a different front clip,(at least a clean straight and rust free one) there was a note in the glovebox stating the trans is original but not saying anything about the motor, from a guy in Colorado in 2005... there are some oil change stickers on the door from Chicago in the 60's, had a Colorado plate, title, and air sticker from the 90's and I got It from a guy in iowa 3 years ago that said he just let it sit for years.

60flatop you made me laugh again, I remember thinking chevies are the best when in high school, now any old car is cool as heck.

and you just don't see any of these old buicks up in my neck of the woods, have never seen a wildcat under the hood before this one. the ones up here rotted away long ago. I always liked the body style and the way these cars look tho. and i really like the running gear in them now that I know a little more more about them.

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A power steering pump rear bracket/brace can be possible (although I don't know specifically what's on the particular model of Buick you have). Might have been a particular thing they were trying to minimize or keep from happening?

When that car was designed, the "center, rear" gas tank filler access was quite common, including behind the rear license plate. Just be glad it wasn't a mid-50s Cadillac or Chevrolet!

NTX5467

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The bracket makes sense, as long as it's being attached to the engine side of the motor mount. Can't quite recall my dad's 65 Electras bracket. But any Electra would provide a clue as to the routing of the same.

The 65 Wildcat is a super car. In my opinion, you are a lucky guy to have one. How about some pictures to sooth the souls here?

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thanks all- i am borrowing a camera from my girlfriend this weekend and my #1 goal is to get some pics and get them posted next week if possible so you guys will see the car is for real.

found a sun tach in a box from 1982 so going to discreetly mount it in the car somewhere and set the redline needle on 4 grand.

thought i heard somewhere the th400 modulater is adjusable with a screwdriver... as in possible to firm up the shifts a little, has anyone ever heard of that? its a tad mushy for me, i put a shift kit in a th400 back in 82 not sure if i want to go that route...

my car is basically a "20 footer" or like number 3 condition but i am super blessed to have it and really enjoy trying to preserve it and prolong its lifespan, but it will never be a show type car so i think a few small performance mods would not detract from it. goal is to always have it driveable in the summer months so i still have 3 months to get her ready ha ha.

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A power steering pump rear bracket/brace can be possible (although I don't know specifically what's on the particular model of Buick you have). Might have been a particular thing they were trying to minimize or keep from happening?

NTX5467

My 64 Riviera has the same brace and it is a substantial piece of steel, probably 3/8' thick. I figured it was for keeping the engine from twisting as it is not needed for the power steering pump. That is held on by a couple of studs off the head bolts.

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4400 to 4600 was the factory shift points for stock 401's around 1965. Gran sport Riv's in 65 raised to 5000.

Your best bet is good plugs, wire, points and proper working carb. Bump the timing ( also an advance kit in

the distributor), make sure the switch pitch switch is working, leave it in drive and go for it!

Good Luck

Bill

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thanks all- i am borrowing a camera from my girlfriend this weekend and my #1 goal is to get some pics and get them posted next week if possible so you guys will see the car is for real.

found a sun tach in a box from 1982 so going to discreetly mount it in the car somewhere and set the redline needle on 4 grand.

thought i heard somewhere the th400 modulater is adjusable with a screwdriver... as in possible to firm up the shifts a little, has anyone ever heard of that? its a tad mushy for me, i put a shift kit in a th400 back in 82 not sure if i want to go that route...

my car is basically a "20 footer" or like number 3 condition but i am super blessed to have it and really enjoy trying to preserve it and prolong its lifespan, but it will never be a show type car so i think a few small performance mods would not detract from it. goal is to always have it driveable in the summer months so i still have 3 months to get her ready ha ha.

The adjustable modulator will alter the shift timing because it only alters the vacuum signal message. The nice thing about a shift kit ( B&M) besides only taking a 1/2 hr. to install is that when the shift lever is in drive, the shifts are just like a stock T-400, it only shifts firm when you are manually controlling the trans.

FYI, all of the GM family when each division had it's own engine with the exception of Chevrolet were designed for torque. The Buick nail head is no different. The stock camshafts and small valves and most importantly it's restricted exhaust passage configuration hold it to 5,00 rpm or less. With a factory cam with the trans in gear under load you would most likely float the valves in a good conditioned engine before it would blow up. You need to remember the Buick nail head is a compromise in the original concept for the engine, that engine was too expensive to build. That engine (1951) 216 cu. in. V-8, aluminum block and heads ( heads were hemi chambers ) made 335 HP at 5,100 rpm. In the image you will see that the Buick nail head production engine retains the intake side of the 216, but only half the piston ( half of a Hemi's piston dome) and moves the exhaust valves to the intake position whereby the exhaust path is highly restricted, Notice on the 216 that the lifter gallery and exhaust side rocker arm angles are unique and in this configuration is much better stability wise than the Chrysler Hemi. Too bad it never made production. see the link;

Buick-XP-300-engine.png

The nail head;

images?q=tbn:ANd9GcTVdQ013ERK1b7Xw8oZsIuzn7jvONMD3ILE6OkX6SGZIM3R1pUS

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Thanks for that link! Although the exhaust port appears to be "restrictive", what I see looks like an "anti-reversion step" in the floor of the exhaust port. That would help keep the intake charge "cleaner" and less diluted with residual exhaust gases as the new intake charge enters the chamber. In the '80s, anti-reversion cones were inserted in some brands of tubular exhaust headers to make carb tuning more efficient and build more power at the same time. Like Ford's Y-block combustion chambers, much of the '50s "high tech" was not fully developed until the '80s, it seems. Still, though, although smaller ports and valves are usually associated with "high velocity" ports, the middle rpm ranges would have benefited, as the upper rpm levels would have been compromised, needing the longer camshaft durations to help compensate for it.

As one Buick factory operative allegedly stated, when asked why Buick still had only pushrod engines when Olds had OHC engines . . . "For our customers, acceleration stops on the other side of the intersection." Don't need high rpms for that. Off-idle torque is what works in that situation.

Chevy used smaller intake valves in their medium duty "truck" engines. 1.72 intakes rather than 1.94s on the 4.00" bore engines. I found some dyno runs sheets for the 1971 model year, which included normal 1/2 ton 350 V-8s and similar C60 medium-duty 350s. There wasn't much difference in the horsepower or torque levels. Possibly the smaller valves gave better mid-range throttle response? Yet dual exhausts, 1.94 intakes, and a larger 4bbl made 50 (advertised) horsepower difference in 1965 Chevy 327 V-8s, with the same camshaft . . . 300 vs. 250.

And there's the issue of rod/stroke and stroke/rod length ratios of the Nailhead vs. the small block Chevy V-8s. Lower rod ratios mean the piston has less dwell time at TDC and exerts a stronger "yank" on the intake charge as it moves downward, which can help compensate for sub-optimal intake port design. Longer exhaust cam event duration can somewhat compensate for the poorer-flowing exhaust ports. A "package deal" for sure.

Enjoy!

NTX5467

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alright- these pics are from spring 2012 which is when i purchased the car in iowa.

the car was located around 375 miles one way from my home in nw wisconsin, found it via a craigslist ad.

i towed the car home with a car hauler trailer and my trusty 77 ford wood truck. the truck has a 300 6 banger in it with a 4 spd.

it was a heavy load for the old truck- max speed was about 58 mph the whole way back with the pedal to the metal most of the way...

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couple more pics

rear 4 trunk body mounts were rotted away...4 about equal hand sized rust holes... rest of trunk was very solid by wisconsin standards ha ha

paint code on car was aqua blue poly.. rear trunk lid was cream, same as front clip, so some parts came off another car maybe not sure of history...

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spring of 2012 was also remodeling house... was lucky enough to get 2 large free picture windows from someone down the road for the price of hauling them away...

we put the brown metal roof on spring 2011... best thing i ever did, snow slides right off. dont have to shovel it off any more thank goodness.

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back to buicks- i decided to start at the back of the car and work my way forward winter of 2012-2013 so i removed the gas tank and started to see what was what-

this was the worst rust i had to deal with...

PLEASE keep in mind i am not or have ever been a body man, a welder or whatever... i work in a warehouse, same one last 32 years and have done mechanical work but never any body work so my results are far from what many achieve on this forum. but maybe i can give some hope to the guy that is on a super low budget and may not have any skills, that you can still be involved in the hobby.

it baffled me how even to fix this without expending much money or getting someone to do it for me at first, but after some thought and lots of time spent on this and other forums i decided to cut out the rotted steel and piece in 1/4 inch angle iron to form the side angles of the body braces and then weld flat steel to the top and bottom.

the way i figure it, at least i am stopping the cancer from spreading and improving the structural integrity of the car which i will prove later.

keep in mind, whomever painted this car in the distant past just covered up all this rot with a piece of sheetmetal from a toyota hood...

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It is probably difficult for some on this forum to understand how anyone could do things on the cheap like this, but I know well of what you speak. I am taking this same approach with my '61 and I know the results will never be show quality, but then that is not what I am after. I just want to be able to drive a piece of history around and be proud in the fact that I did most of the work myself.

Also the '65 model big Buick's were among the most unique ones ever made IMO. With the excellent styling and single year instrument cluster design, they stand apart in these respects. If I ever get my '61 done, that is probably the next Buick I will be looking for. I do have a hankering to do an old Ford first though, just to be different. LOL

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Shift firmness is controlled elsewhere other than the vacuum modulator, from what I recall. "Mushy" shifts are just part of many GM automatic transmissions, compared to the "firm" shifts which some shift kits make happen.

A friend of mine did the B&M shift kit, about $50+ back in the early '80s. It was firm without the harsh shockloads which the $10.00 shift kits (same time frame) gave . . . manual L to manual 2 would chirp the tires on their Z-28s at part throttle.

One thing controlling shift firmness is the accumulator spring. The accumulator is in the fluid circuit to cushion the sudden "apply" oil flow for that circuit. Mopar Performance's shift kit (for the A-904 family automatics) says to leave the spring out all together. It did make things a little firmer and quicker, but not harsh by any means.

One of the old "shadetree" quick-shift-fixes was to drain the Dexron fluid out and put Ford Type-F fluid in its place. The Type-F fluid doesn't have the "initial slip before lockup" which Dexron has, so it makes for a nicer shift in the older THM400 automatics. I understand the blue B&M fluid has similar shift feel, for more $$$.

Remember, too, that a prime criteria for all automatic transmissions, back then, was the "imperceptible shift". You heard the engine rpm change, but didn't feel anything as the vehicle kept on gaining speed. The THM400 did a good job of this, too! Yet the other design criteria was to not have an overly-hard shift, even at WOT, plus a "easy engagement" into "D" or "R" . . . what the old Lexus midnight informercials called "shift shock". "Easy engagement" can be related to the basic line pressure of the transmission, which does have some internal adjustment to it.

Also remember Buick's customer demographics, back then, associated "smooooooth" with Buick, hence their love of the DynaFlow transmission for many years. If they'd wanted "more noticeable" shifts, they could have had an Olds with a Hydramatic, by observation.

You might start with a fluid/filter change. When I added some GM Automatic Transmission Conditioner to the THM350 in my '77 Camaro, it shifted a little more like my friends Z-28 with Type-F fluid in it. Slightly quicker and firmer. Remember, too, that your current fluid, if it's been in there for a while, might have gained a little viscosity over time. Newer and more "watery" fluid might ease the quickness of the fluid flow in the valve body, possibly.

To have the vacuum modulator correctly adjusted, you'd need a pressure gauge tapped into the appropriate fitting on the side of the transmission case, PLUS a GM service manual to tell you which line pressure range is operative for your general altitude . . . which is what it's purpose is anyway, to vary line pressure with altitude changes and lower related horsepower output due to the thinner air "up there".

Enjoy!

NTX5467

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Pretty nice looking car! I concur about the styling of the '65-'66 full-size Buicks. They look good in convertibles, too!

There's a LOT that can now be done with tools you can find at many auto supply stores, plus the various rust coatings and sealers. Much more readily-available now than in prior decades, it seems. Many YouTube DIY videos, too, plus the "Saturday morning" cable tv shows.

Good luck!

NTX5467

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Also remember Buick's customer demographics, back then, associated "smooooooth" with Buick, hence their love of the DynaFlow transmission for many years. If they'd wanted "more noticeable" shifts, they could have had an Olds with a Hydramatic, by observation.

NTX5467

They could have along with Olds, a Pontiac or Cadillac as all used the same automatic. The original Chevrolet Powerglide and Buick Dynaflow goals were the same. " A seamless no shifting of gears all done through the converter" . Remember the original Powerglide 1950-1952 started out in high gear and let the converter multiply the torque.

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