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548 build

  1. #1
    BTC cardcarrying member SuperSoaker's Avatar
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    Default 548 build

    I'm thinking of doing a 548 build
    I'm looking at two sets of pistons
    Mahle coated pistons w/13cc dome or
    Srp w/10cc dome.

    trying to run pump gas 91/93oct

    the Mahle with a .038 gasket .005 in the hole .043 quench = 10.45 to 1 or
    .051 gasket .056 quench = 10.21

    the Srp w/.038 gasket is 10.24

    Is the coated piston worth giving up .013 quench


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  3. #2
    BTC cardcarrying member SuperSoaker's Avatar
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  4. #3
    steelcomp was here
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    Not IMO. Keeping the quench where it does the most good will help offset whatever added risk of detonation a few extra tenths of compression might cause. The coating in and of itself isn't worth any compromise.
    If God is your co-pilot, change seats!
    Acts 2:38, the perfect answer to the perfect question.

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    New here Beer:30's Avatar
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    Proper quench, in itself, can deter detonation at higher compression levels. Looks like double-checking for raised/sharp areas in the chamber and a nice aluminum head would be your main concerns.
    Quote Originally Posted by gn7 View Post
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    BTC cardcarrying member SuperSoaker's Avatar
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    I will be running a set of AFR heads

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    Senior Member MACHINEHEAD1's Avatar
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    Great head choice. 10.5 is fine with about .035 piston to head, 91/93 octane and cold water plumbing. Run the SRP out of the hole to get your 10.5

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    gn7
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    I am confused. Are you saying that you need to run the .051 gasket with the mahles so you can lower the comp ratio .2? Are you saying you don't think you can tune around a .2 increase in compression? Order the AFR with the CNC chamber option, they'er 3cc larger



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  10. #8
    northern member Canuc's Avatar
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    wouldn't .035 be a little close with a 4.500 piston in a boat motor ? does the coating allow for a little tighter piston to bore ? just asking never used it. wouldn't think speed-pro or mahle bother putting it on if it was good for nothing , or is the stuff a gimick ?
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  11. #9
    gn7
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    Quote Originally Posted by Canuc View Post
    wouldn't think speed-pro or mahle bother putting it on if it was good for nothing , or is the stuff a gimick ?
    If it is, it's a very expen$$$$ive gimmick



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    you can do all the math in the world as to deck height and comp height but until you get that assembly togather you really dont know you true piston to deck clearance until then. and check every hole and i really seen some blocks that are off,deck from one end to the other, and canuc is right .035 is too close for a big bore motor the piston will rock and kiss the head,i would look at .040 min and more depending on piston to wall clearance and rpm of the motor

    good luck roger

  13. #11
    gn7
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    Quote Originally Posted by Canuc View Post
    wouldn't .035 be a little close with a 4.500 piston in a boat motor ? ?
    Quote Originally Posted by flat601 View Post
    canuc is right .035 is too close for a big bore motor the piston will rock and kiss the head,i would look at .040 min and more depending on piston to wall clearance and rpm of the motor
    good luck roger
    Where does he say that he is running .035 total?



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  14. #12
    BTC cardcarrying member SuperSoaker's Avatar
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    Min. quench will be .043 The SRP pistons that were in the motor had a compression distance of 1.270 and were .005 in the hole so the new piston will have the same 1.270 with a .038 head gasket.
    I'm just trying to get the comp. at around 10.0 / 10.25 to 1 so I can run safely on 91/93oct. I normally run 34deg of timing. AFR 305 w/cnc chambers and pockets that were milled .008 so chambers should be around 120cc.

    Anyone running 10.5 to 1 on pump gas at sea level???

    I'm looking at the Mahle coated piston with a 13cc dome.
    Or the SRP with a 10cc dome.
    I'm leaning towards the SRP

  15. #13
    Boat Nut sleekcrafter's Avatar
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    Quote Originally Posted by SuperSoaker View Post
    Min. quench will be .043 The SRP pistons that were in the motor had a compression distance of 1.270 and were .005 in the hole so the new piston will have the same 1.270 with a .038 head gasket.
    I'm just trying to get the comp. at around 10.0 / 10.25 to 1 so I can run safely on 91/93oct. I normally run 34deg of timing. AFR 305 w/cnc chambers and pockets that were milled .008 so chambers should be around 120cc.

    Anyone running 10.5 to 1 on pump gas at sea level???

    I'm looking at the Mahle coated piston with a 13cc dome.
    Or the SRP with a 10cc dome.
    I'm leaning towards the SRP

    I'm at 6 - 700ft running flat tops & 114 cc heads cut .008

  16. #14
    BTC cardcarrying member SuperSoaker's Avatar
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    Quote Originally Posted by sleekcrafter View Post
    I'm at 6 - 700ft running flat tops & 114 cc heads cut .008
    Thanks sleek

    I'm having a hard time getting a 10 to 1 set up with 120cc heads.

    10.4 or so no problem getting. I may go with a flat top 9.3 to 1 and say fu$k it.

    Need durability and reliability as we will run for a mile or so at WFO and do 30/40mi at a time one way

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