Can not tune 1970 Buick 455 GS

Discussion in 'Classic Buicks' started by Tom Hoenig, Aug 18, 2021.

  1. Bens99gtp

    Bens99gtp Well-Known Member

    With that much unmetered air coming in sounds like you have a rich idle condition for sure. There is no way to add that much and it be smooth without it being rich
     
  2. Tom Hoenig

    Tom Hoenig Well-Known Member

    I agree with the "hemet on fire" analogy. But I was trying to add things up. #1 why did the exhaust header gasket blow out on the driver side? #2 The temp sensor is going off at the correct temp of 205 to 225 degrees and has been a problem from day one. #3 325 degrees seems high for the intake temp, even at the exhaust crossover point. (remember there is no spring restrictor on the exhaust to push exhaust back that way) #4 every time I start the car all gas is boiled off and have to crank to get new fuel from the pump. #5 plugs show lean condition. I am lost here but something is telling me this intake manifold is the issue. With zero history on this car I have traced the 455 block to be a 1972 vintage and the intake manifold to a 1970. I am suspicious that something in the intake manifold is not lining up right. I know this is a mind bender, but the engine seams to be tight and good running at 3000 rpm going down the road to be a cam or valve issue. No skip and very smooth. It also idles smooth in neutral. As soon as you put it in gear or engage air conditioning load it falls apart, unless you run at 900 rpm at 16 degrees advanced timing which pings like crazy. I did not want to pull the motor on a 100% restored car, but it looks like the only solution at this point. Any advice for a crate motor swap?
     
  3. Tom Hoenig

    Tom Hoenig Well-Known Member

    It is the craziest Motor I have ever seen. The plugs show being very lean, yet the huge vacuum leak I intentionally create increases the idle and does not drop my overall vacuum on the gauge. I need to do more tests, because something is missing here.
     
  4. CJay

    CJay Supercar owner Staff Member

    You had the pcv installed. Try it without the valve in place.
     
  5. Bens99gtp

    Bens99gtp Well-Known Member

    Its not hard to pull the intake off, just pluck it and see, but 300+ there isn't crazy high.....sooner or later you goingbto have to dig in there and see whats up, but given the vacuum your talking about it has a not very radical cam.


    The in gear issue could not be motor at all, it could be converter.

    All cars will idle better with more timing plain and simple......if yours likes 16, then simply limit it on top end to 30-32 and be good
     
  6. CJay

    CJay Supercar owner Staff Member

    You have hot exhaust gas running through the crossover. It's normal.
     
  7. charlierogers

    charlierogers GSX stage 1 4 speed #149

    hey tom, maybe it would be a good idea to give yourself a break from the car for 3-4 days. a fresh mind that is not aggravated is your BEST friend. after that i would start with cam check with Jim.w advice. from there you can always replace the int gasket if you think its compromised. its easy to get overloaded when you get aggravated then you start jumping all over the place. we have all been there at one time. most of the time these problems are pretty basic and straight foward to diagnose if you follow the rules! best of luck.
    charlie
     
  8. Brian Albrecht

    Brian Albrecht Classic Reflections

    It's been a while but I believe the water jackets are different starting in '72...at least the heads are.
     
  9. Bens99gtp

    Bens99gtp Well-Known Member

    There is some differences but all year will swap, there might need to be a few holes coolant and air holes in the later years going on earlier blocks but nothing I've heard of to cause running or temp issues
     
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    A wide open PCV hose WITHOUT the PCV valve in place should stall the engine all by itself. My engine won't run with that big of a vacuum leak. There is engine exhaust running through that crossover, 319* is not abnormal. Very strange.
     
  11. Smartin

    Smartin antiqueautomotiveservice.com Staff Member

    That's why I was thinking the carb is dumping fuel with nozzle drip or floats are too high.
     
  12. GSX 554

    GSX 554 Gold Level Contributor

    Or the secondary plates are stuck slightly open ???
     
    Smartin likes this.
  13. Brian Albrecht

    Brian Albrecht Classic Reflections

    IMG_0462.jpeg
    Normally, I would agree, but the photo shows an abnormally excessive amount of heat. There is a milling, year model, gasket, backpressure, issue going here IMHO.

    Or, conversely...

    Excessively hot exhaust gasses from wrong timing (JW) or vacuum leak (OP) creating lean burn.

    Either way, that manifold looks like its too dang hot at the crossover. OPs other observations support that as well.
     
    Last edited: Aug 30, 2021
  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    If the engine is running lean, exhaust temperatures will be hotter. The paint burning off the intake is something I am used to seeing. What I can't explain is how it can run with a vacuum leak the size of 3/8" fuel line.:) That screams RICH to me.
     
    Brian Albrecht likes this.
  15. CJay

    CJay Supercar owner Staff Member

    Larry, he had the pcv out of the intake. Not disconnected from the carb.
     
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You might be right Jason, but that is the reason I asked, and that isn't what he said.
     
  17. CJay

    CJay Supercar owner Staff Member

    Must of read it wrong. Too bad the car isn't in my driveway. I'd fix it for a 12 pack
     
    Max Damage, Smartin and TrunkMonkey like this.
  18. Brian Albrecht

    Brian Albrecht Classic Reflections

    Thought you might still be busy putting in an electric fuel pump for an ignition problem...:D
     
  19. CJay

    CJay Supercar owner Staff Member

    Im a big proponent of testing and diagnosing. Too many parts changers. Drives me nuts.

    Brett happened to buy a robbmc pump and sender from me. He had been complaining of a fuel delivery issue as well. Hence the reason he bought the parts from me.
     
    1973gs and Brett Slater like this.
  20. Brian Albrecht

    Brian Albrecht Classic Reflections

    Weren't you (maybe you still are) in the diagnostic business?
     

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