ive been reading quite a bit and every book i turn to says 10:1 compression is severly pushing the limits for pump gas. ill be running around 10.5-10.6:1 and really dont wanna blow up......i have alumnium heads so that helps bit not a ton. am i gonna be safe?

 

It's up there. But entirely doable (for pump gas, that is).

When you did the calculations, what thickness did you use for the head gasket?

 

im running 10.6 in my iron headed 406.It runs great compression reading is 200lbs

 

well i just used my best guess thats why i said 10.5-10.6. i havent decided what thickness to use but porbably closer to the thicker side to keep it down as much as i can.

i just got worried everytime i read something it says 10 is pushing it.....


but that 10.6 on your iron heads makes me fell much better

 

Sorry to hi-jack the thread, but what is the stock head gasket thickness? I have an '88 LB9, and will be porting a pair of heads to install soon and am thinking about upping the compression a tad bit.

 

Factory steel shim was about .018", more or less, depending on part numbers. Aftermarket gaskets, such as the ones from Fel-Pro are .039" (for the standard rebuild). They can be had in other thicknesses, though.

If it were me, I would mill the heads rather than use a thinner gasket. To me, the gasket is for sealing. The head cc's make or take the compression.

 

For some good info on this check out kieth blacks site they have comprission calculators there and some excellent info on quench height wich is very important.they say to stay as close to .040 as possible.So considering you stock deck height puts your piston .025 in the hole,then the stock metal shim gasket (.015-.018) it puts you right in that area.Putting a composition gasket on a stock un decked block puts ya at around .065 which is too much.This is according to KB site.

PS i also read at that site that too high of a quench hight also causes detonation.ie a engine with 9 to 1 and too high of a quench height will detonate before an engine with 10 to 1 with the proper quench height.

 

Interesting, maybe I'll just leave it alone then. Maybe I should drop the compression a little bit instead to accomodate twin turbos in the future