Jcollison016

Hello! This is my first post I'm John from Baltimore Maryland, I just started piecing together a 6.0 engine lq4 block and I need some help with selecting parts/milling to accomplish my goal of about a 11:1 static compression. I'm getting a set of l92/ls3 heads (which I don't have yet so suggestions are welcome). It's an all motor build going in a s13 Nissan Silvia. So what milling will have to be done to the head and what pistons should I go with, the cylinders are a bit scored so they are at the machine shop now waiting to be taken .030 over. Will a dished piston with almost decked heads do this? Or should I get flat tops with relifs? This is my first ls build so I'm in the dark on piston/valve clearances right now.
Thanks!

gagliano7

The dish pistons don't help with ptv. I would get flat tops with reliefs so you can get better compression. Then you can mill the heads if you need to up compression and still have room for a bigger cam if you want since you would have the reliefs.

Mercier

iTrader: (15)

^^ This. LS3/L92 style heads already have typically larger combustion chambers than most of their cathedral port analogues. Combine that with dished pistons and you will have low compression. Look at Cam Motion's website..cammotion.com. There is a text link at the very bottom for "engine calculators" and they have a neat free Windows app that lets you put in your combustion chamber, piston volume, deck height, gasket thickness, etc. And play with it until you get what you want compression-wise. All the what-ifs a guy could dream of.

imma_stocker

iTrader: (19)

Didn't mill my L92 heads.

Pistons are +3cc with valve reliefs
OEM LS9 headgasket
11.2 or so SCR


If I did it again I'd jack compression up to 13-14 and run E85.

Jcollison016

Do you know the thickness of the ls9 gasket? And if I'm running 93oct what do you think I could bump compression to safely

Mercier

iTrader: (15)

LS9 gasket is 4.100" bore and .051 compressed. If you are after compression specifically, I would look at more like a LS2 gasket or similar with a smaller bore to fit your 4" bore block. It doesn't seem like it would affect it much, but that extra 0.100" x .051" will drop compression measurably. Download that calculator(it's free!) and put your numbers in. I think it will open your eyes.

Jcollison016

I'm hoping to get the calculator as soon as I can get to my laptop! I'm on my phone for now. That will dial my comp goals in. Is there a OEM set of rods I can use on aftermarket pis tons for the lq block? I have to get rods and pistons anyway, and I don't really see the rods as a weak point on a na build so I'm hoping so save some dollars there.