bbeck

So, I'm in the process of putting together my next LQ4 6.0L with a bigger cam and some 243s to raise the compression. I wanted to target 11:1 compression, so I was thinking of milling the 243s and running cometic gaskets. However, I can't seem to find much information on PTV. I will clay to double check the clearance once I get the heads. But, I'm buying them and going to have the work done before they're sent to me.

So, with the following cam specs:
0.651/0.651 lift
227/231 duration
114 LSA

Has anyone run something similar to help make the decision of how much can be milled and if/when the pistons will need to be flycut?

bbeck

Anyone running 243s milled with a cometic gasket on stock lq4 pistons have any measurements?

FloridaWS6

I don't have any measurements but I run-LS1
-CompCam 236/238 605/617 113+3
-243 Heads milled .030 / valve job

Hope this helps

bbeck

Awesome, thanks man. Any idea on how much clearance you had and if you had to flycut the pistons?

FloridaWS6

Didn't have to touch the pistons and I can't remember the clearance off the top of my head

FloridaWS6

But you shouldn't have to worry about clearance until around 12.5:1+ compression (with what cam your talking about)

bbeck

I was thinking of going with .030 mill and valve job on the heads and running a .040 or .030 cometic to get some decent compression on the motor. just want to be sure that the mill will be fine before having them sent off for the work.

HighLiner

iTrader: (1)

Is that a off the shelf grind?

FloridaWS6

Should be fine

MYSTIC-1SC

iTrader: (14)

PTV clearance has a lot more to do with duration than lift. With the cam specs listed I don't see you running into any clearance issues but its always a good idea to measure. How much clearance you have will be dependent on what gasket you run and how much you decide to have the heads milled of course.

Aaron @ Thompson Motorsports

AINT SKEERED

iTrader: (2)

I ran a .045 gasket and 60 cc dart head with 2.05 valves on my lq4. I had .80 int and .190 exh. clearance with an f14 cam 232/234 .600 lift 112lsa +4
if you mill to 61 cc and a .040 you will get 11 /1 or so compression and have plenty clearance
intake side seems to be the same as a flat top but the exh. side falls into the dish part of the piston.

bbeck

I think I'll do .030 mill and clay it to get an idea of how thin of a cometic I can go with.

HighLiner

iTrader: (1)

Who's going to do your machine work?

rpturbo

iTrader: (47)

I also have a lq4 w/ 799's. My cam fit no problem, but no where near as big as yours. See my sig for specs. My heads were touched I think .010. Stock LS9 gaskets. I want to say I had over .100 on the exhaust, but don't remember 100%.

Pachuco SCT

Im a bit late but was wondering if I mill my 243s to 62cc with a btr stage 2 227/234 .614/.576 113+2, and I was told with a .045 gasket. Does that sound good.