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Discussion Starter #1 (Edited)
I have been having issues with some backfiring and general rough running. I was adjusting the idle mixture to see if power valve was at issue and one side would kill the engine when screwed in. On the other side it had no effect screwing it in or out. What should i do next? Holley street avenger on 350 cid.
 

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Sounds like it needs a good cleaning.Idle cir. is plugged in the metering block.
When you take it apart to rebuild/clean up. You can use Low air pressure to back blow the metering block. If you still have a issue you may need to replace the metering block. hope this helps.
 

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Discussion Starter #3
I wll try that. I need to mention it began intermittently and got continually worse until it won't hardly run at all.
 

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I would do compression and leak down test on you're engine to make sure the engine is in good condition first. RICK
 

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Vacuum test will diagnose that problem pretty quick. Last week I broke out the old vacuum gauge because I was putting up with a poor idle terrible response and part throttle hesitation. I thought it could be the carb so I took apart the holley cleaned and reassembled checked the timing fired it up and guess what?... Problem was still there! IT was very frustrating to say the least... I connected the vacuum gauge did some tests with it and noticed that at idle with the engine warm with timing and carb settings correct the gauge needle would max then slowly drop 1-2" and it did this regularly. So I decided based on what the trusty vacuum gauge was telling me to check the plugs. It was time for new plugs anyways in my mental service record since I had a set on the shelf anyways. Maybe with my commuting to work I had forgotten to change them last oil change. But I swapped them out and I have a happy good running Nova again. Hook up that gauge and see what it does!
 

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Do the simple things first...

Pull the air cleaner off and back the idle screws out 3 to 4 turns... Next run it up to a high idle... 2500 to 3000 should be enough. Now, with your other hand shut the choke plate off until the engine nearly dies. This will place a very high vacuum demand on the circuit and usually pulls small pieces of gunk through the system. See if you can set the idle screws normally.

If this doesn't work you can always go the next step.
 

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Discussion Starter #7
Tanks all. Turned out afterall to be the ributor. MSD 85551 full of rust. Don't know how it ran at all. I see many others with the same problem . Any Ideas? I am not interested in quarter mile but would like dependable that has some get up and go when you ask for it.
 

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hrmm.. try a decent stock replacement chevy hei man.. if your not racing,,, those bad boys are great to 5500/6000 rpm and last forever... like 100 bucks for a real nice one too.
 
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