71 vs 72 350 hp

Discussion in 'Small Block Tech' started by Dr. Roger, Feb 27, 2022.

  1. Dr. Roger

    Dr. Roger Stock enthusiast

    So my understanding is that the stock 71 350 was 275 hp, whereas the 72 was 195 hp. What was done different in these motors. They had the same compression. Was it a timing/carburetor difference? Maybe I have the stats for the 70 instead of the 71. Thanks.
     
  2. DaWildcat

    DaWildcat Platinum Level Contributor

  3. sean Buick 76

    sean Buick 76 Buick Nut

    Yes this is correct. The only measurable change between the two engines was the way the power was measured. Both engines were 8:1 compression. All of the pre 71 engine ratings were massively over rated. With the exception of a few under rated engine setup to keep insurance costs down most engines from all brands were over rated not on purpose, just by testing being crude and un-applicable. The post 71 dyno testing was much more accurate. We have done dyno tests on a 74 buick 350 that was rated at about 150-165 Hp I don’t remember and it had a true modern rating of 165 Hp after we pulled it from a junkyard car and tested it. We then added a turbocharger and hit 350 Hp with no other changes.

    the 71+ engines simply need a few things to wake them up:

    1. boost

    2. if not boost then the huge dish pistons swapped for high compression versions

    3. cam swap, the cam was terrible in these. tA 212 or better

    4. just the tune up alone was hugely killing HP numbers. I’m positive that headers, dual 2.5 and a tune up would give a 20-40 Hp jump over factory ratings.
     
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  4. Dr. Roger

    Dr. Roger Stock enthusiast

    Thanks guys. I am wondering if there was any real difference in hp between 71 and 72 350s. Wonder if the stock cams were the same.
     
    sean Buick 76 likes this.
  5. sean Buick 76

    sean Buick 76 Buick Nut

    I’m sure there’s no difference between the actual output on the two engines. If there is a difference in the cams it’s only to reduce exhaust emissions. Either way a TA-212 cam is better than stock.
     
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  6. Jim Blackwood

    Jim Blackwood Well-Known Member

    According to my '76 Chilton's manual:
    In '69 the 350 was available in 9:1 (2bbl) and 10.25:1 (4bbl)
    In '70 it was available in 9:1 (2 and 4bbl) and 10.25:1 (4bbl)
    '71 to '76 they were all 8.5:1

    This checks with my recall. Except for some isolated exceptions '70 was the last good year before smog engines took over. Note also the rpm at the HP rating. It dropped significantly. Primarily due to the introduction of the catalytic converter. So it was a combination of factors including compression, cam profiles, additional smog equipment, the change to ported advance, and more restrictive exhaust systems.

    Jim
     
  7. gsjohnny1

    gsjohnny1 Well-Known Member

    and you had the a.i.r pump. that alone makes a big difference in hp. my 73 stg1 stock went 15.5 in the 1/4. disco the pump was good for 15.0's. go 1/2 second faster takes a big jump in power
     
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  8. Fox's Den

    Fox's Den 355Xrs

    I used to race this guy that had a 75 Regal with a 350 and my 71 would just smoke him and that was with my slow out of the hole bigger cam and 270 gears out back. the fun days with 15+ second cars. maybe more like 16's lol
     
  9. Mike B in SC

    Mike B in SC Well-Known Member

    One of the car magazines did an interesting test after the new low-compression '71's came out. They got identically optioned cars, one a 1970 GS350 and the other a 1971 GS350. They wanted to see what advantage, if any, the low-compression car had over the high compression one. One test driver drove the 70 and another driver followed in the 71. The driver in the 70 just drove normally and the guy in the 71 was just supposed to keep up with him. They found that the 71 had to be driven harder (more throttle) to keep up with the 70, which caused it to get worse fuel mileage. I think they found no advantage the 71 had over the 70 other than being able to run on regular gas. It was slower, worse throttle response and got less mpg.
    I need to find that magazine and post it. It was an interesting article.
     
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  10. Jim Blackwood

    Jim Blackwood Well-Known Member

    Those results applied pretty much across the board in those days. I had a '70 Cutlass and the question was, did the disc brakes on the '71 offset the engine? General consensus was that it didn't.

    Jim
     
  11. Dr. Roger

    Dr. Roger Stock enthusiast

    It would cool to see dyno results from a bone-stock 70, 71, and 72 350.
     
  12. sean Buick 76

    sean Buick 76 Buick Nut

    On a modern (crank rated) dyno properly setup I would expect 280 Hp from the 70SP code 4bb, 240 Hp from the 71-72 4bb, 210 for anything later with a smog pump, 180 for the 75-80 engines with the worse heads.

    The compression ratio drop in 71 hurt HP for sure, also fuel mileage went down and fuel octane requirement also went down. Keep in mind the camshafts after 70 were setup to lower emissions, not looking for torque or HP. They literally lowered the compression beyond low, and made the cams so tiny that they couldn’t make power over 4000 RPM. Even with twin turbos we couldn’t get a stock cammed 9:1 350 to make power above 4600 RPM. Swapped in a Poston 114 cam (similar to a TA-212 and it made 460 Hp to the wheels at 5900 RPM.
     
    Last edited: Mar 1, 2022
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  13. Fox's Den

    Fox's Den 355Xrs

    My 71 had no problem baking the right rear tire with TA Radials and a 2bbl. Put that cam in with headers and 4bbl could bake that right rear for a block. slapped in a 373 gear and baked both tires, all with that low compression, you guys worry too much about numbers.

    Stick that TA 112s in there and have a real powerhouse time to step up. out the box
     
  14. alec296

    alec296 i need another buick

    Basic the rating is the difference. The engine 71 and 72 are pretty much the same.
    Some porting on heads, mill the deck some, a crower level 3 cam degreed 4 advanced, more converter, tuning distributer recurve and carb jetting, the outcome can provide a possible 250 or better, which has been proven several times with a skylark running mid to 14 second flat quarter mile times. 71-72 engines would be better off with oiling modifications and a fresh front cam bearing.
     

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