my table numbers.

[brokenujoint]

well with my stock cam and valve train. 677 sealed power .020 pistons, 258 crank and 707 rods my numbers on the ratio calculator as as such:

liter: 4.56
SCR: 9.58:1
DCR 7.93:1
Quench .0655. thats without cleaning up the CC i take it.


how do these numbers sound? what grade gas can i expect?

[Cheromaniac]

I have the same crank/rods/piston combination but my block wasn't decked so the deck clearance is 0.045", the quench is 0.088", and static CR is 9.25:1. I can run 89 octane without pinging on a 120*F summer day using the hottest Champion RC12LYC plugs. You should be able to run the same grade of gas.

[brokenujoint]

ok after learning that my victor gasket is a 44 and my pistons are 14 here are my revised numbers

bore 3.895
stroke: 3.895
combustion chamber 59cc (very mild clean up on the combustion chamber)
deck: .021
gasket : .044
pistons 14cc
stock cam

liter 4.56
SCR: 9.83
DCR : 8.13
quench .064


89 octane do-able?

[Cheromaniac]

89 octane do-able?

That would be pushing it if your SCR/DCR numbers are correct. It's more likely you'll need 91 octane. I cc'd two of my 677P pistons and both came to 17.5cc. By comparison, the stock pistons were 13.1cc.

[brokenujoint]

why are some of you guys saying the 677's are 14cc and some are saying 17 ? what are they?

[gradon]

Go to your nearest rite-aid or cvs and buy a 10cc syringe. Squirt the first 10cc of liquid in the dish and then pay attention to how much of the 2nd 10cc you put in to get your total(you might not be able to distinguish .5cc, but you'll know the difference between 14 or 17). I don't put it past the tech dept to give wrong data or repeat data that has been entered wrongly in the system--I just was told the different dishes of the 677s, 802s, 825s, etc and that info is more current than Dino's, right or wrong. So you said that the deck clearance was measured to be .021"--this means you had .024" removed from the block, right?

[brokenujoint]

no thats piston to the top of the block. not including the 0.044 gasket. .021 + .044= .065 quench. thats how you determine it correct?

[gradon]

.0215" is the piston to the top of the block on a stock 4.0. Now that you have a longer stroke, shorter rod, and different pin height, the piston has moved and so now it would be ~.045" from the deck, unless your machinist removed .024" to get it to .021".

[brokenujoint]

my piston at TDC sits at 0.021 from the top of the block. machinist didnt deck it. it was resurfaced but not decked. the undished part of the piston. the part that sits nearest the actual block, it measures 0.021 from the top of the block. now if it had been decked before i bought it, i dunno. thats what i got.

[Cheromaniac]

the part that sits nearest the actual block, it measures 0.021 from the top of the block. now if it had been decked before i bought it, i dunno.

I think that's quite likely.