Quote:
Originally Posted by PGSigns
The oil can be coming from the intake gasket, a weak spark from a bad plug wire can give you the oil issue. Based on dyno results on circle track crate engines with that head and a dual plane intake the vortec head engines suffer from some lean holes. My race engine builder used to do a lot of em and when I was having a lot of vapor lock issues with my L31 and the same intake and carb you are running he suggested a change based on dyno results. We switched to a Super Victor intake and a Holley 670 street avenger carb. The intake is not huge and the runners are a perfect match for the heads. Vapor lock gone, better all round performance and the vapor lock issue is gone.
Jimmy
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I'm not a Holley fan at all, but switching to the 670 Street Avenger probably solved 95% of your vapor locking problem. Look at how the two carbs store fuel and you'll see why.
Quote:
Originally Posted by SunSoaked
Exactly! I agree with what you're saying 100%.
IMO, if the outer cylinders are lean while the inner ones are rich, that is NOT a tuning issue you can adjust out of the carb. It's poor design characteristics of mismatched parts. I firmly believe that Vortec style intakes were designed to be used with port injection not TBI. That's why I asked the question regarding GM using TBI with Vortec manifolds.
Like you, I believe a weak plug or wire can cause oil buildup and eventually lead to a misfire. That's why I went thru the ignition system first.
Regarding the 120 psi readings. I thought that was low too. I don't know what my compression ratio is (Goodwrench engine with Vortecs)? I'm guessing somewhere around 9:1? However, I only pulled the plug on the cylinder I was testing. Had I pulled them all and cranked it over 4-5 revolutions, I suspect it would be up in the 150+ range. Since all three had the same reading, I'm not concerned with the numbers.
A leak at the intake manifold is plausible. I had not thought about that.
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Your cold start issue is definitely in the tune, this is fact. All intakes carb'd or otherwise will have lean/rich spots. If you put individual O2 sensors on the headers of my Z28(LS swapped), you could see that even the LS6 intake will do that.
What is your max RPM? You could probably get by with a smaller carb, have better velocity for fuel distribution, and a crisper throttle response.
Not trying to split hairs with you on this one, but comparing a max effort circle track engine to a DD isn't even in the same ballpark. Single and dual plain intakes work better at different RPM ranges.