Quote:
Originally Posted by 1970camaroRS
I love answering this question. To be honest, I aquired the LQ4 with the intentions of running L92 heads, but one heck of a deal came across my plate and I had to take it. The heads without valve springs only ran me $650 shipped and I already have the springs, locks and retainers I was going to use on the L92s. They were also recently redone and milled for a smaller chamber, which is a must on the LQ4 with dished pistons to bring up the compression ratio.
Here are the technical reasons that made the final decision for me.
1. The valve size on this head is only 2.0" as opposed to the giant 2.16" valve on the L92 meaning I can run a much more aggressive cam before running into PtV issues.
2. The runner volume is 30cc less than L92s meaning more port velocity and more torque, especially on an engine that might not have the highest compression ratio in the world. Or cubic inches. This is a street car after all.
3. They flow within 10 cfm at peak and 5 cfm everywhere else of the stock L92s. I will be giving up a few peak HP in trade for more torque, but I will make up for it with the camshaft.
4. My LS6 heads will use my stock rockers that I already have. If I had a larger budget I'd get the needle bearings replaced, but I'm just going to have to sit on this one. They checked out good during inspection anyway. No need for offset rockers that L92s need.
5. Did I mention that they were $650 shipped?
-Nathan
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Very much agree with your thought process. The L92/LS3 suff does seem to turn a higher peak hp # but the the cathederal ports often have a higher peak tq and broader curve mostly due to velocity.
Since I did my heads and cam ls1 6 years ago I have also noticed a trend on ls1tech and the LSx world in general to go with a big cam that get the hp #s but does not have the curve to go along with it. A well thought out LS6 heads and cam can turn some great #s. Looks like you have a solid plan.
If you have not already done so and decide to go for more cam, search Ls1tech for topics on dynamic compression, a calculator was floating around IIRC PianoProdigy posted it. Depending on the static compression of your LQ4 with the milled heads you can get more greedy on the cam. Good luck on the build.