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830 Competition too lean?

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  • 830 Competition too lean?

    Howdy all. I've got an 830 race carb I got from a buddy of mine that's like new. Running it on a 427 in my Chevelle. 10.5:1, 311°/238°-.577" on 110° lobe cam. New RPM Air-Gap intake. MSD 110 GPH Holley mechanical pump. The whole setup is new for me, as I was used to running small blocks in the past. Timing is at 10° idle and 34° full mechanical advance. (That was recommended by MSD pro.)

    Here's the deal. It's way too lean. I've got to pump the heck out of it to start cold or even pour some gas in top. Starts fine when it's warm, and will idle fine then too. I've got the air screws out 3.5 turns. Drove it about two miles normal driving and it would fall on its face, if I pushed it to half throttle too quickly. I checked the plugs and it was too lean.

    Opened it up and found no power valves & 78/78 jets.

    I added a 3.5 & 5.5 power valves and re-jetted to 82/85. Drove it another couple miles and it responded better with a quick tap of the throttle, but still not well. Check plugs again and still too lean. Almost looked like I made no adjustment at all.

    My brother (whose opinion I respect a lot) says he thinks I've got a vacuum leak that's leaning it out. I find that hard to believe with all new stuff. But I don't have much vacuum either.

    Could it be that I need to jet this thing that much higher still? Or did I somehow end up with bad $300 RPM Air-Gap intake manifold? Any thoughts?

  • #2
    Can you change air bleeds? Smaller would enrich it.