LQ4 w/ L92's Problem
 

Well i just recently swapped a set of L92 heads on my LQ4 and i have a problem... my car didnt go any faster in the quarter.

My original setup was this: LQ4 shortblock, stock cast iron heads w/ LS6 springs, comp 222/224 566/568 cam, edelbrock performer intake, holley 770 street avenger carb. The car also has a 2200 stall and 3.50 rear gear. With that setup it went a best of 11.97 @ 113mph.

Then i installed a set of untouched L92's w/ patriot golds, and a gm single plane carb intake. The car now went 12.03 @ 114mph ... so virtually the same.

My guess is that the cam probably isnt right for the heads. Also it only goes through the traps at about 5600rpm so it probably need about a 4.10 gear to bring up to 6500 or so. Im also guessing that changing to such a large port and a single plane, it probably lost to much bottom end. I realize that an LS3 intake and fuel injection would probably gain a lot in the low and midrange but i would like to stick with the carb for now.

Anybody got suggestions or have similar results?

the cam definately isn't right for the heads. L92's like a large split duration cam, somethin like a 224/236 high lift (around 600+). Have you milled them any? You prolly wanna mill them .020 or so to bump up your compression.

Yeah i figured that the cam was most likely the main issue and i would like to wait on milling the heads until i build up the short block. I was also concerned that my carb might be borderline small for this setup.

Also, i was wondering if the victor jr. for the L92's has any power advantages over the GM intake or if they are pretty close to the same.

carb should be fine assuming you don't rev past 7k... does it have 4 corner adjust?

talk to pred z about a custom cam

yeah its a 4 corner adjust and i only rev it to about 6700 because im still on a bone stone shortblock.

was the preload on the lifters within specs-did the 60' times slow up, also 1/8

I just borrowed a dial indicator from a friend the other day to check the lifter preload but just havnt got it done yet. When i put it together i put them at zero lash and i had to turn them 1 1/4 turn till they were torqued and i read that is about perfect but i will still check it. I lost about a whole tenth on the 60' and i dont remember what the 1/8 was.

A bigger stall would help you out a lot.... 2200 is almost stock...

yeah a single plane and my 2200 stall dont match to well. It would be great if someone would make a dual plane for these heads because switching to fuel injection and the LS3 intake probably wont be in the budget for a while. I hope that changing the rear gear from a 3.50 to a 4.10 might squeeze another couple tenths out of it.

You need a custom cam for that single plane intake also, they like a lot of overlap. Really need to look at a better matched cam and yes, a more aggresive stall will help also.

You are only about 9.7:1 with the L92 heads on the dished LQ4 pistons.