Got it running

Discussion in 'Race 400/430/455' started by BuickGSrules, Apr 23, 2021.

  1. Bens99gtp

    Bens99gtp Well-Known Member

    Well some replacement cast heads don't have to be expensive. I have a pair or 73 with factory stage1 valves listed, I would have them serviced and valve job done......given your higher compression id polish the chambers smooth to make sure nothing to form a hot spot is left, and then add enough head gasket to drop the numbers to live on pump gas.

    I'm certain a stk set of heads could also be located. All in your shoukd be well under 1000.

    With a stk style dist a plate can be dabbed up to locate all 4 pins that the springs go on........remove the weights and clip it in.......I would set it though about halfway through its swinging arch to try tonhelp make sure the rotor phasing wasn't to one extreme or the other....msd make adjustable rotors and caps to correct this but not sure how or if those parts retro fit back to stk units.

    I know you said you tried doubling head gaskets.......but you didn't say how thick the gaskets were..........if you double the steel shim stk gaskets your not even to a standard felpro thickness

    So I started doing some math...if you have 0 deck, a standard .039 gasket, and the normal flat top with valve pockets your head cc have to be about 56cc to get to 13.0:1.........now with dished style pistons that start out 20ish cc b4 notches......assuming only 20cc the same setup nets you 11.3:1......if you go to the piston out of the hole. 010 and the thin .017 steel shim gaskets with 56cc heads your at 12.3........you can not physically get the piston and head much closer......there are only about .007 apart there....even there you still need to shave another 4cc to get close to 13:1........I've never heard of a buick head being cut that much.

    So are we sure its actually 13:1. Cause its starts to seem almost impossible to get there if it has dished pistons. I'm not doubting, just trying to make sense of this
     
    69GS430/TKX likes this.
  2. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    That is good advice IMO. I have been reluctant to replace the heads because I was told they had lots of hours of porting done, so I didn't want to throw away that investment. But if would make the car a lot more streetable, I will start saving my pennies and think about starting over with some saner heads, like yours possibly.

    I have not studied that subject much. I will lot into it. It sounds like a good idea.

    I am pretty sure they were not the steel ones. I was trying to lower compression as much as possible without creating problems or spending a lotta dough.

    Thanks for running those numbers. I was told the engine had 13:1 by people who helped build the motor, but who knows how accurate the claim is. All I know is that it has always been a bear to re-start when hot, it pings badly under acceleration, and when it's idling the exhaust out the tailpipes feels like shotgun blasts on your hand (without the BBs). Cold compression test using the spark plug gauge shows about 180 + or -10 PSI, but I understand that doesn't help much in calculating actual compression ratio.
     
  3. BQUICK

    BQUICK Well-Known Member

    If you run vacuum advance at idle it will run cooler and also when you shut it off timing will go away. Also allows for smaller throttle opening for a given idle speed which will help it shut off.
     
    69GS430/TKX likes this.
  4. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    That makes sense, I will definitely do that. Thanks for the suggestion.
     
  5. 69GS430/TKX

    69GS430/TKX Silver Level contributor

    Thanks for that info. How close to zero deck are those pistons?
     

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