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Thread: piston to head clearance

  1. #1

    piston to head clearance

    i recently freshened my 383 chevy up. its got a internally balanced forged crank, 6.0 eagle rods, and je pistons. its a 12.1 vortec headed motor. i shift @ 5700 and go through the traps @ 6300. i`m now running depending on which piston and where you measure it in the hole ( on the top or bottom of the block deck) with head gasket installed from.030 to .042 . the motor had 200 runs on it and bearings were really not even broken in yet...my point being there wasnt alot of odd movement on the bottom end . crosshatch was still real clear in cylinders. soo , .030 is a calculated risk of what level?

  2. #2
    Senior Member RACING JUNKIE
    Join Date
    Jan 2006
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    I wouldn't even worry about deck clearance, if you have .030 to.040, i would worry more about valve to pistion clearance, i've run .020 out of the blk with .043 gaskets, but had enought valve clearence. I almost always run out of the deck, except with alum rods.

    JMO

    Zip.

  3. #3
    i checked the deck height just so i could calculate the squish. i went from a .040 compressed thickness head gasket to a .028 and i was concerned that i might of made it too tight..... a had a .015 set in my hands too. realistically at the low rpm its turning i`m not real worried but ya never know. piston to valve is real high something like .175 and .110.

  4. #4
    Senior Member RACING JUNKIE
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    In the old days GM used a steel shim gasket, only about .015 thick and put them on the street for thousands of miles.
    The one engine i ran .020 out was and alum blk. with steel rods and it was turning about 7500 rpm's thru the lights. I put 200/300 runs on the engine with no problems. As long as you have very little piston rock it should be o'k with .028 clearance.

    JMO

    Zip.

  5. #5
    Senior Member MASTER BUILDER
    Join Date
    Jan 2007
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    Batesville Ms.
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    167

    Clearance

    Iagree with ZIP. Later J.Smith 4621 racing

  6. Racing Junk


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