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Thread: New Engine, New Carb Problems

  1. #1

    Default New Engine, New Carb Problems

    I have a new GM performance 350 crate engine, Vortec heads, dual-plane intake, Holley 670 vacuum secondary carb, mild cam and HEI ignition. All came as a complete engine. 9.0:1 compression, and cam specs are 215°/223° at .050 .473" lift with a 108° LSA. I have timing at 10° BTDC and idle mixture screws 3+ turns out balanced. If I adjust mixture screws in to say 1 1/2 turns engine will not idle well especially when in gear. Also smells really rich when backing in garage. I also have a problem with the engine running on after shutting down. I shut down in gear to avoid.

  2. #2


    Sounds like you need to play with the timing/vacuum advance. So if your at 10° initial, is your total 31°-32°? Most HEI distributors come with 21° mechanical advance. So with that being said, what's your vacuum can set too at idle? Is it plugged into the manifold constant vacuum source? At three turns out, it'll be rich on idle mixture. I had a Vortec 355 with Comp 270HR cam, HEI ignition, and I had the screws at 1.25 turns out. Initial was 16°, 32° total all in by 3000. My vacuum advance plugged into manifold vacuum added like 8°, so I was idling at 24° initial. I think your right on at 10-12° initial, add some advance with your can. What's your jetting? Power valve?

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