monte383sbc

iTrader: (15)

i finally got my mahle -4cc pistons in with my stock crank and ls2 rods, now i checked my deck height and i came up with .011-.012 deck height will i have enough room with .040 cometic head gaskets which would be .028-.029 quench? also this is gunna be my daily driver with 11:1 compression and running on 93 octane. any help apprciated thanks matt

itsjustaSB

iTrader: (13)

i would try and keep it in between .035 and .038 for the quench seems tight to me from everything i have read

1989GTA

IMHO that is to tight. However you probably will find a few people running that tight. I think you will find that most people shoot for .035" to .040". Maybe trim .006" off the pistons?

davidws6

iTrader: (36)

Daily Driver ? What's your rev limit set to ?

I'd say .030 is the min but you'd prolly be ok if you don't rev it crazy...

monte383sbc

iTrader: (15)

i guess it looks like iam goin with a different head gasket then, anyone intrested in new cometic 3.910 .040 head gaskets?

crainholio

iTrader: (2)

0.040" compressed thickness, and you're calculating 0.028" quench?

Did you deck the living daylights out of the block, or are you running whacky pistons that are 0.012" above deck?

mark21742

I'd run a .051" gasket to get as close to .040" quench

Bad Notch

iTrader: (3)

Damn, I'd trade you my new .045 Cometics for your .040 if your interested.

crainholio

iTrader: (2)

If the pistons really are 0.011" out of the hole because of decking machinework, and he'll be revving the snot out of it, sure.

I'm hoping he will re-check his math, though. I've never seen a Mahle piston with crazy deck heights, they like that #1 compression ring to have plenty of safety margin.

Running tight quench is great for combustion efficiency and detonation resistance as long as the rods are up to it.

monte383sbc

iTrader: (15)

let me recheck my d/h , ive bin told a few different ways to check it, what is the corect way to check my deck height?

monte383sbc

iTrader: (15)

i may take you up on that trade after i check my deck height agin, thanks

LLC

How are you checking it now?

monte383sbc

iTrader: (15)

i checked it buy putting the piston at true TDC and rockin it bak in forth with a dial indicator on each side to get it straight up, the i used a tru straight edge and ran a feeler gauge under it, ill recheck it tommorw

Sales2@Texas-speed

iTrader: (5)

From my experience, it's not real unusual at all for Mahle's to set up .005-.010" out of the hole.

OP: What piston part number are you running?

jmm98LS1

iTrader: (28)

My mahle flat tops sit .012" out of the hole with just a light cleanup pass on the decks.....

99LS6SS

iTrader: (4)

I thought a tighter quench was better. I'm glad im reading this thread

1989GTA

"I thought a tighter quench was better."

It is but you can have too much of a good thing. You do not want the pistons hitting the heads as that can result in broken parts. As said above it appears most builders shoot for the .035 to .040" range. If you have the money and time you can sneak up on the quench and see when the pistons just start to kiss the heads. Most of us except for the racing teams don't have the money or time to experiment for such a small gain.

monte383sbc

iTrader: (15)

iam not sure ill try to get the number tommorw

monte383sbc

iTrader: (15)

ok i checked my deck height again for the 50th time and iam coming up with .010-.011 out of the hole with the piston flat, and i came up with .023 rocked on one side and .024 rocked on the other side, soooo what is the minimum gasket i should go with .045 cometics, i have a set of .040s but that seems to tight of a quench, thanks for the help matt

1989GTA

.045" between the two. A smashed piston can ruin your day.