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Thread: 427 BBC Piston Questions....?????

  1. #1
    DansBlown73Nordic
    Ok im going to be building this 427. It will a be a 454 block with a steel 427 crank with a set of oval ported heads. The block should clean up at .030.
    The problem is that I can't find 427 forged pistons for a open chamber head. I have looked in Jegs and Summit. Some guys say you can run closed chamber pistons with a dome in a open chambered head. My machine shop guy says its a bad idea.
    I even looked into a Hyperutectic but its the same deal. I want to end up around 10 to 1 compression. Can anyone give me any ideas.

  2. #2
    Thunderbutt
    Dans66Stevens:
    Ok im going to be building this 427. It will a be a 454 block with a steel 427 crank with a set of oval ported heads. The block should clean up at .030.
    The problem is that I can't find 427 forged pistons for a open chamber head. I have looked in Jegs and Summit. Some guys say you can run closed chamber pistons with a dome in a open chambered head. My machine shop guy says its a bad idea.
    I even looked into a Hyperutectic but its the same deal. I want to end up around 10 to 1 compression. Can anyone give me any ideas. Dan, My motor was a 427 I had open chamber heads with 13 to 1. so I don't know what you're saying

  3. #3
    Fiat48
    Maybe your confusion of not finding the pistons is the stroke. 396 and 427 same stroke of 3.76". Summit showing 4 different forged pistons in Speed Pro alone. Jegs showing some also.
    Closed chamber, open chamber = piston all the same, dome is different.
    SRP piston part number 152148 has 30 CC dome.
    With a .030 overbore, .042 head gasket with a gasket bore diameter of 4.310, the block decked to 0 deck height and assuming your open chamber heads are 119 cc's = 9.95 to 1 compresion. Herbert Performance has the pistons.
    [ March 23, 2003, 04:18 PM: Message edited by: Fiat48 ]

  4. #4
    GofastRacer
    Dan, Summit catalog, page 95, 427 Open Chamber, "TRW-L2308AF30" Race piston with.585 dome, floating pin $399.60.
    11.52 Comp 116.9 CC Chamber
    11.26 Comp 119 CC Chamber
    10.69 Comp 124 CC Chamber
    Those are the ones I have in my 427 also!.. wink
    [ March 23, 2003, 04:04 PM: Message edited by: GofastRacer ]

  5. #5
    DansBlown73Nordic
    The problem is that those pistons all put me around 11 to 1 compression. That is to much. Im not even sure if 10 to 1 is going to be ok. The guy at Summit said to just cut the domes off. eek! Im thinking I just spent $400 for pistons and now Im cutting them up.
    I do have a 119 cc head. I also have a set of 113cc. They just make the problem worse.
    Am I correct in thinking 10 to 1 is all I can run with pump gas?

  6. #6
    Fiat48
    Also be aware that TRW and Speed Pro calculate these compression ratio's using a deck height of .008" and a compressed gasket thickness of .028" with a gasket bore diameter the same size as the bore itself. In other words, not the real world but a ballpark.
    Most engines are not .008 in the hole.
    Head gaskets are rarely the same diameter size as the bore. IE. 4.280 bore = generally closest bore size of head gasket available is 4.310. And I guess the gasket thickness compressed is the stock Chevy stamped steel, which nobody uses. Felpro head gasket compresses about .042.
    Doing the math on the TRW piston Gofast has comes out 43cc's.
    [ March 23, 2003, 04:45 PM: Message edited by: Fiat48 ]

  7. #7
    Fiat48
    Dans66Stevens:
    The problem is that those pistons all put me around 11 to 1 compression. That is to much. Im not even sure if 10 to 1 is going to be ok. The guy at Summit said to just cut the domes off. eek! Im thinking I just spent $400 for pistons and now Im cutting them up.
    I do have a 119 cc head. I also have a set of 113cc. They just make the problem worse.
    Am I correct in thinking 10 to 1 is all I can run with pump gas? "SRP piston part number 152148 has 30 CC dome.
    With a .030 overbore, .042 head gasket with a gasket bore diameter of 4.310, the block decked to 0 deck height and assuming your open chamber heads are 119 cc's = 9.95 to 1 compresion. Herbert Performance has the pistons."

  8. #8
    DansBlown73Nordic
    Am I correct in thinking that 10 to 1 is the most I should run?

  9. #9
    Fiat48
    I can't help you on that. I run gas in my little pickup, lawn mower and generator. I would suspect you would have to run a octane booster of some type.

  10. #10
    West Coast Dave
    Know of numerous guys running 10:1 up to 10.5:1 w/ iron heads and w/ full 34 deg timing on pump 92 octane. W/ aluminum heads a few guys are going w/ 11:1 on pump w/ no pinging/detonation. I'd stick to the 10:1 w/ pump gas w/ the way the gas is going. Here in Cetntral Cal we used to get 93 @ the pump, lowered to 92 and now it's 91 w/ all major brands.......sucks

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