Feel Pro vs Cometic head gaskets

Discussion in 'Street/strip 400/430/455' started by 70 GMuscle, Jun 15, 2019.

  1. 70 GMuscle

    70 GMuscle Plan B

    I was reinstalling my heads when I noticed the cometic head gaskets have half of the coolant holes over fuel pro 1125.
    Plus all holes except ends were steam holes
    2 per side.
    No coolant flow between center cylinders.
    Not sure what to make of it.
    Have had great luck in past.
    But I held off installing.
    Calling on Monday.
     
    dan zepnick likes this.
  2. 70 GMuscle

    70 GMuscle Plan B

  3. hugger

    hugger Well-Known Member

    What compression?
    Are you using the .027 cometic to up compression.?
     
  4. 70 GMuscle

    70 GMuscle Plan B

    Yes
    And not sure what the point you mean.

    But holding gaskets against each other shows very different coolant flow.
     
  5. hugger

    hugger Well-Known Member

    What I'm getting at is if it's under 11to1 I wouldn't use the cometic unless you are using the cometic in the .027 to bump the compression up In Which case your kinda stuck using them,..but yes they have smaller holes,..it doesn't cause any issues that I've noticed i have also drilled them out iirc also been awhile since i messed with any,..

    Got 3 pair on the shelf but not there to look
     
  6. Bens99gtp

    Bens99gtp Well-Known Member

    I used a set with no issues, but only in dragracing where I normally have ample cooling time
     
  7. Jim Weise

    Jim Weise 1000+HP

    Guys,

    The design of the cooling system dictates that the water enters the front of the block, traverses the entire length of the block, and is transferred up into the head by the slots at the rear of the block/head.

    The coolant then comes back forward in the heads, to the intake, and out to the radiator. The coolant needs to follow that path, to absorb the heat from the cast iron. The small holes in the gasket are only there to eliminate airlocks, they are inconsequential in cooling system performance.

    JW
     
  8. 70 GMuscle

    70 GMuscle Plan B

    Thank you for taking the time to explain guys.
    This had me puzzled compared to the fel pro.
    When I go home I will inspect again.
    My second mistake is bore to small.
    Ordered for stock bore and my block is.040 over.
     
  9. 70 GMuscle

    70 GMuscle Plan B

    Engine is about 9.5 to one.
    73 block piston .036 in hole. Heads milled .020.
    New stock stainless size valves w bowl work.
    Street car.
    Only race at Buick event I hope at Cecil or Atco
     
  10. 70 GMuscle

    70 GMuscle Plan B

    So is it safer to stay with fel pro 1125 or get correct bore cometic .027?
    I can’t use new cometics as good for stock bore.
    My mistake.
    Fel pro 4.385
    Block is .040 over according to piston. Speed pro forged.
     
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Stock bore is 4.3125. .040 over is 4.3525. Felpro gasket bore is 4.385. I don't see a problem. My engine is .038 over and uses the Felpro 1125 gasket.
     
  12. 70 GMuscle

    70 GMuscle Plan B

    That is what I used before. 1125 fel pro
    Looking to build a little compression and better quench.
     
  13. Schurkey

    Schurkey Silver Level contributor

    .036 + .027 = .063. You have no quench. You lay out one of your gaskets on two layers of aluminum foil, cut all the holes and trim the edges, and two layers of foil would get you quench. I won't promise that it'll seal worth a crap, though.

    You aren't going to get adequate quench distance until you cut the block, or raise the piston crowns. Any "quench" distance greater than .045 or .050 is worthless.
     
    Last edited: Jun 16, 2019
  14. 70 GMuscle

    70 GMuscle Plan B

    Thank you
    Would need flat top pistons I understand.
    Just working with what I have.
    Trying to optimize it if possible.
    Car ran well.
    Would like a little more.
     
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Change the pistons. Get some custom Diamond or Autotec pistons with the right compression distance. That will get you to zero deck. Those speed pros are dinosaurs. Do they have valve notches?
     
    WE1 likes this.
  16. 70 GMuscle

    70 GMuscle Plan B

    Come on man. I appreciate all your advice.
    Just upping what I have a bit. Car has gone 12.30@109 w junk. 1.69 60 ft. May never again.
    But just wondering on best head gaskets.
    I will sell my cometics to who wants them.
    I will get exact specs this week when I reenter garage.
    I guess 1125 it is . Better safe than sorry.
     
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    The 1125 is Felpro's better head gasket. Not sure there is anything to gain by just swapping head gaskets for whatever small gain in static compression. How is your distributor advance curve and exhaust system? I'd look at that first.
     
  18. Bens99gtp

    Bens99gtp Well-Known Member

    Normally going form .040 to .027 is worth about .2 compression.

    Most street type motors in the these hp levels see about 4% in each point. So on a 500hp motor 4% is about 20hp for 1 point. Those gaskets are 1/5th that, so about 4hp give or take a little
     
    300sbb_overkill likes this.
  19. StfSocal

    StfSocal Well-Known Member

    To piggy back on this topic, i am running .019 in the hole, and looking at .027 Cometics. This would put me at .046 quench. I have the FelPro .040 from TA in the garage but that would put me at .059. Either way i am not "optimal" at under .045 and at this point there is no cutting more off the block nor switching out pistons.

    If these engines came with such a crappy quench to begin with i am sure it will live, but just not be optimal correct?
     
  20. sailbrd

    sailbrd Well-Known Member

    I have to defend the old SpeedPro pistons. Been running them in my supercharged motor for 4 years now. They may be heavy but are darn tough. No, I am not using them in the "big" motor we are building.
     

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