LS6427

iTrader: (2)

I want 10:1 cr out of my 390ci.

I know the crank is 3.825", bore is 4.030", rods are 6.125", head chambers are 65cc.

What piston?

((yes, I'd ask my builder, but he's closed....LOL))

Thanks.

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Stumped1215

iTrader: (9)

You need piston cc, deck height, and head gasket thickness

LS6427

iTrader: (2)

I;m trying to figure which piston I need.....

So .051 gasket thickness....LS9 gaslets.

Deck height I guess is whatever a new GenIII LQ9 block is.......

*****and...I think 10.5:1 cr is what I want. As I'll be using E85 with 18psi.*****

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Stumped1215

iTrader: (9)

http://www.wallaceracing.com/cr_test2.php


I'm getting about 8cc dish with the piston .008 above the deck

LS6427

iTrader: (2)

What did you use for deck height?

What for valve relief/dome? Isn't this what I'm looking for to choose the proper -cc piston?

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Stumped1215

iTrader: (9)

ok -.008 deck height is the piston sticking up out of the hole 8 thousands which should be fairly close using shelf parts, but this makes a big difference on compression so it really should be checked before the heads go on.

4.030 bore
3.825 stroke
65cc head
10cc dish
.051 gasket
4.060 gasket size
-.008 deck

exactly 10.5:1

LS6427

iTrader: (2)

Ok, thanks. I guess the only change would be 4.100 gasket size. LS9 gasket.

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