fast89stang

iTrader: (2)

If we have lq9 and stock pistons, milled heads. 050, how much comp should we have? Building a max effort lol another one, for another buddy. Looking to get cam ideas from tooley or tick or? ??? Somebody Soon.

dogsballs

I go roughly 0.6:1 per 30thou.

So guess up 1.0

Or cc heads and do it properly

Doug G

.006 per cc and measuring them would be the right thing to do.

Running the numbers and shavin' .050 I' m looking at 11.3:1 with everything else stock. Approximately

speedtigger

iTrader: (16)

I find it better to do it the way Doug said as the compression change per thousandth goes up as the compression ratio gets higher.

Sales@Tick

iTrader: (3)

You know how to get a hold of me sir!

speedtigger

iTrader: (16)

If you are using an LQ9 with Stock 71cc heads. My figures look like this:





So, 11.05:1 using the oft quoted .006" milled off = 1cc formula.

Doug G

Steve, to keep my math easy, I just input all the stock info and then reduce the gasket by the thickness to be milled. Kind of a down and dirty method. LOL works up to a .050 cut

speedtigger

iTrader: (16)

Don't be mad for me saying, but that is why you got it wrong. If you notice, the combustion chamber does not take up the same amount of surface area as the gasket.

The stunningman

iTrader: (47)

speed is right about the gasket giving more than the mill. However stock diameter isn't 4.060 on a GM 6.0 head gasket. Its closer to 4.100. On L92 heads the edges of the head chamber are larger than a 4.060 gasket (not that it presents a problem). The GM 6.0 gasket is larger than the chamber.

speedtigger

iTrader: (16)

Depends on which gasket you have. The 12589227 is the original ls2/LQX series head gasket which I believe is 4.060". The 6.2 liter LS3/L92 gasket has a larger bore and is part number 12610046 which I remember being 4.080". I have used both. Then there is the 12622033 LS9 head gasket that is advertised as 4.100"(I have never tried that one). Either way, it only makes a few hundredths of a compression point.

Doug G

The calculator I used doesn't ask for a gasket bore diameter. So not taken into equation.

You have the deck height at -.006....I used 0. I see this is where the difference comes in.

I adjusted the one I used to input a stock LQ4 compression of 9.43:1, that is where I got the 0. With the -.006 I get 9.55:1

I also have to ask...with the combustion chamber shape being what it is, how can a single number (.006) equal a set amount of increase ?
I can see it to a point, but wouldn't it increase once you get past that point ?

So, yes, really should measure to be sure.
No argument here, and no feelings hurt.....I'm not a machinist by trade

fast89stang

iTrader: (2)

i think this project is put on hold. We have taken apart 2 motors, one had a broke crank and the block was damaged. The other had a busted piston and had some cylinder damage. I found him a LY6 on Ebay for 1750 plus 175 shipping, but he didnt buy it.