L92/L76 Head milling ?
L92/L76 Head milling ? Want to get a set of L92/L76 heads for my lq4 swap but dont want to loose to much compression cause i have 2.5 5.3 heads 61cc my question is have far can i mill the l76/l92 heads
IF you plan on putting in a decent cam I would check piston to valve clearance first. The big 2.160" valve eats it up quick. I milled mine .030 and couldn't fit much of a cam in it, others have had more room than I did. So just make sure to check.
heads Ok i know i cant get them down to 61cc i just want to stay medium 10s in compression kinda middle of the road and also dont want to be limited with my cam choice not sure of compression ratio now i get different numbers when i use the calculator so input on that would be great.
Last edited by Quick99TransAm; Apr 3, 2010 at 03:53 PM.
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Dont mill then. Airflow and camshaft matter more than compression IMO. I would rather have 10:1 and the option to put in a larger cam, than 10.5:1 with limited camshaft selection.
But lucky for me I wanted a smaller camshaft. PLus everyone else is also seeming to find that smaller cams work better with L92 heads.
But lucky for me I wanted a smaller camshaft. PLus everyone else is also seeming to find that smaller cams work better with L92 heads.
When I had .030 taken off mine, they came in at a bit over 63cc's (10.5:1). The factory blueprints that I have show 68.4cc +- 1cc. I ran my old 222/238 XER lobe came with .045 Cometics with no PTV issues.
With my current cam (234/246 EPS) I am running .052 stock head gaskets, no PTV issues, my 6800 rpm shifts would find that for me in a hurry. It was only worth about .3 cr increase from the thinner gaskets. I am running 29* of timing right now with no knock. Once I get back to the strip I will add and subtract a couple of degrees to see what that does.
Excellent driveability and idles at 850.
You need to be realistic with your goals for the car. My old car was ok, but very weak up top, ran out of air with these heads. Low MPH showed that at the strip. On the street it was fine. The new cam already shows a difference in the VE and MAF tables. Much more air flow. I have a ported L76, 100mm LS3 MAF with a Amsoil oil-less cone filter. My kPa drop is only 2 kPa.
Just measure your own parts, part stack up is different on all mass produced engines.
With my current cam (234/246 EPS) I am running .052 stock head gaskets, no PTV issues, my 6800 rpm shifts would find that for me in a hurry. It was only worth about .3 cr increase from the thinner gaskets. I am running 29* of timing right now with no knock. Once I get back to the strip I will add and subtract a couple of degrees to see what that does.
Excellent driveability and idles at 850.
You need to be realistic with your goals for the car. My old car was ok, but very weak up top, ran out of air with these heads. Low MPH showed that at the strip. On the street it was fine. The new cam already shows a difference in the VE and MAF tables. Much more air flow. I have a ported L76, 100mm LS3 MAF with a Amsoil oil-less cone filter. My kPa drop is only 2 kPa.
Just measure your own parts, part stack up is different on all mass produced engines.
219/235 .607/.621 113+5
This is key, tolerance stackup can have a large impact. Thats why anyone swapping cam should check for themselves.
This is key, tolerance stackup can have a large impact. Thats why anyone swapping cam should check for themselves.
Last edited by SweetS10V8; Apr 4, 2010 at 09:22 PM.
So is it impossible to get 12:1 compression with L92 heads on a LQ4(even with aftermarket pistons)? I wanted to get new pistions installed in my LQ4 later this year and I wanted a little more compression. I'm not trying to run a monster cam either.
go for a domed piston that still has releifs in it. problem is finding pistons with a valve relief in it for the big valves under stock 6.2 bore. (4.065). finding a domed piston in 4.030 that has 2.165 releifs in it is gonna be tough. ($$$) if you do find them.
Eric from HKE said he might know of a piston that might get me the compression I want, I was just wondering what everybody else was doing and what others thought about it. I also looked in the Wiseco catalog, and they have a piston that might get me in the 10 or low 11 range.