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  1. #91
    techinspector1's Avatar
    techinspector1 is offline CHR Member Visit my Photo Gallery
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    Quote Originally Posted by States View Post
    I thought I was following your recommendations but I must have gotten off base somewhere.
    Eau contraire my friend, it was me who dropped the ball. I went back and read the entire thread a little while ago and found the point where my brain froze up. It was in post #63 on page 5 where I put the OK on those H618CP030 pistons. As soon as I had the part number, I went to the Summit site to see what the compression height was. Satisfied that it was 1.560" and failing to take notice that the crown was ( -3.5 cc's), I blessed them. I must have been in a senior moment or a semi-coma to put the OK on those pistons. They would work OK on 72 or 76 cc heads, but will not work with 64cc heads on pump gas.

    I feel like an idiot for misleading you, but rest assured that it was not intentional.

    Please refer back to post #50 on page 4. That should be the flavor of the build. I recommend a zero deck in that post, but if you cannot afford to cut the block decks at this time, then use a Fel-Pro 1094 steel shim head gasket on the virgin block, after being assured by your machinist that the block decks and cylinder heads are flat enough to retain a steel shim gasket. There is a limit to the waviness on the block and heads that a steel shim gasket will tolerate. Assuming a stock piston deck height of 0.025" (piston crown to top of cylinder with piston at top dead center) and a gasket thickness of ~0.015", squish/quench should be finalized at 0.040", allowing maximum detonation protection on pump gas.

    The reasons for cutting the block decks to zero are twofold. One, it corrects any mis-machining at the factory and Two, it preps the block for aluminum heads at a later date. Aluminum heads, when used on an iron block, suffer from differing expansion rates than the block. This leads to slipping and sliding around and the grinding off of the softer aluminum material (called fretting). A thicker composition gasket will absorb this movement and protect the aluminum head from fretting.

    Now, to explain further, when you use a thicker composition gasket, which is normally 0.039" to 0.041" compressed thickness, you are looking for a zero (0.000") deck height between the block and the piston crown so that the squish/quench is in the 0.035" to 0.045" range for maximum detonation protection when using pump gas. The piston deck height is at zero and the gasket thickness is 0.035" to 0.045". A Fel-Pro 1003, at 0.041" compressed thickness is one of the gaskets recommended by several aluminum cylinder head manufacturers to be used with a zero deck.

    Now you will understand that with a stock piston deck height of 0.025", you cannot use a thick composition gasket on the motor, because adding the stock piston deck height to the compressed thickness of the head gasket (0.025" plus 0.041" = 0.066") will create a squish/quench that is much too wide to be effective at preventing detonation. Remember, we want a squish/quench somewhere between 0.035" and 0.045". So, if we are not going to cut the block decks and will be willing to run steel shim gaskets for use with iron heads, we must remember that we cannot leave the block decks stock and later on run aluminum heads with the required thicker composition gasket, because the squish/quench will be all wrong.

    This is why I urge anyone building a small block Chevy to use a 1.560" minimum piston, cut the block decks to zero and use a 0.035" to 0.045" compressed thickness gasket. Even if you run iron heads for the rest of the time you own the motor, there will come a time to sell it and it will sell much easier if the block is decked for aluminum heads and composition gaskets.
    NTFDAY and johnboy like this.
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  2. #92
    States's Avatar
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    Thanks for the explanation. Can you give me a recommendation on either a specific piston of the specs on what I should be looking for to achieve the compression ration I'm looking for.

  3. #93
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    It's all on post #50.
    .
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  4. #94
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    Almost have all the parts in hand. Got the KB pistions, new high flow water pump, HEI ignition and wires..and many more. One item I am having trouble finding is Valve Covers for vortec heads with scorpion roller rockers. It seems like every where I check I get a maybe or maybe not. Any suggestions?

  5. #95
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    Quote Originally Posted by techinspector1 View Post
    Eau contraire my friend, it was me who dropped the ball. I went back and read the entire thread a little while ago and found the point where my brain froze up. It was in post #63 on page 5 where I put the OK on those H618CP030 pistons. As soon as I had the part number, I went to the Summit site to see what the compression height was. Satisfied that it was 1.560" and failing to take notice that the crown was ( -3.5 cc's), I blessed them. I must have been in a senior moment or a semi-coma to put the OK on those pistons. They would work OK on 72 or 76 cc heads, but will not work with 64cc heads on pump gas.

    I feel like an idiot for misleading you, but rest assured that it was not intentional.

    .
    Sir: I salute you.
    You're a good man.
    It takes balls to publicly admit you were in the wrong, and apologise as humbly as you did.

    You've certainly got my respect.
    I can only reiterate: you're a good man.
    And I salute you for it.
    NTFDAY likes this.
    johnboy
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    '51 Ford school bus. Chev 400 ci Vortec 5 sp manual + Gearvendors 2sp, 2000 Chev lwb dually chassis and axles.
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