408 head gasket question

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Oct 11, 2010 | 05:27 PM

331stroker

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408 head gasket question

Guys, I need to verify what compression I will yield using a Cometic custom gasket with a 4.060 bore, .070 thickness.
I built a 6.0 (LQ9) 4.030 bore, Eagle stroker crank 4.00 stroke, Eagle ESP 6.125 rods, Wiesco -8 pistons, 0 deck, 64cc chamber LS6 heads.
I don't have the cam specs. It is a TR224 cam(112 lobe separation). So, if you need the degree at which the intake valve closes at, I don't have it.
I came up with around 10.63:1 Is this correct
I appreciate any help.
Regards,
Jim M

Oct 11, 2010 | 05:37 PM

bww3588

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i came up with that, using just a quick calculator found on the internet. however, i have one question, do you have custom pistons? if not how did you acheive a 0 deck?

Oct 11, 2010 | 07:02 PM

331stroker

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Wiseco part number K394X3 is the part number in there catalog. I believe it was K394F3 when I ordered because of the coatings they are putting on them now...
Ray Little from RayMac Racing Engines did the machine work and assy of the rotating assy.

Oct 11, 2010 | 07:20 PM

bww3588

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if they arent custom pistons, you have a negative deck. meaning the piston sticks above the deck surface. if he milled any off the deck, they are sticking more above the deck.

Oct 11, 2010 | 07:21 PM

bww3588

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if you know exactly how much was removed from the deck, i can give you a more accuate compression ratio.

Oct 11, 2010 | 08:02 PM

331stroker

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The pistons, at top dead center are flush with the deck...I checked them myself.
I am a Chief Inspector on heavy industrial gas turbines. I have a depth mic and straight edge.

Oct 11, 2010 | 08:08 PM

bww3588

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ok, if that is the case, then no material was removed from the deck. the 6.0 block has a 9.24 deck height and the rod piston combo you have comes to 9.24, so it would only be flush if the deck of the block is stock. with all that, the 10.63 CR is accurate.

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Oct 12, 2010 | 10:15 AM

331stroker

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Thanks guys... I have my answer... I was using different engine compression calculators and getting different numbers. One would say 10.63 the other would say 12.97. Closer investigation revealed I was inputting the piston dome data inwrong in one of them. One calculator would say use a - for a dish piston. The other says to use a - for dome piston.
I wasn't paying attention to the details. My mistake..
Thanks again,
Jim M