Saturday Night Racer - 4.3 chevy Question

Pearson_79 LMR Senior Offline Bako Hobby Stocks Rule! Posts: 296 Bakersfield,Ca	4.3 chevy Question 07/23/09 at 3:37pm I am getting some backfire through the carb at higher rpm. Is this valve float or a timming issue? The entire ingnition system is brand new from HEI to plugs. also have a random miss once about every 5 seconds at idle.
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TALON75 LMR God Offline DO IT INTHE DIRT Posts: 735	Re: 4.3 chevy Question Reply #1 - 07/23/09 at 6:00pm sounds like a bad valve, possible bent .
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2Xhobby LMR God Offline W F O racing Posts: 982 Bakersfield	Re: 4.3 chevy Question Reply #2 - 07/24/09 at 2:14am Or a burnt valve.....
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Andrew LMR God Offline 2006 SMS M.S. champion... more of a PB these days Posts: 1359 Camarillo	Re: 4.3 chevy Question Reply #3 - 07/24/09 at 7:59pm Do a wet/dry compression test. If it's a bad valve the wet and dry numbers will be close if not the same.
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Pearson_79 LMR Senior Offline Bako Hobby Stocks Rule! Posts: 296 Bakersfield,Ca	Re: 4.3 chevy Question Reply #4 - 07/25/09 at 8:35am Andrew could you explain the wet dry compression test? There is only aprox. 45 min on a new rebuild and its cranking between 143 and 156 on the compression tester.
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Ensign3

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Re: 4.3 chevy Question
Reply #5 - 07/25/09 at 9:21am

You would do a normal compression test. Then put about a cap full of motor oil in each cylinder. If the rings are worn, the oil takes up some of the difference and raises your compression reading. The oil won't help valve sealing. A cylinder leakage test (leak down test) will help pinpoint where compression is leaking off. Use a harbor freight stethescope and listen at dipstick tube for rings, carb or throttle body with throttle open for intake valve sealing and exhaust pipe for exhaust valves. Also make sure that distributor isn't too worn.

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Pearson_79 LMR Senior Offline Bako Hobby Stocks Rule! Posts: 296 Bakersfield,Ca	Re: 4.3 chevy Question Reply #6 - 07/25/09 at 6:16pm Ok Thanks, I will try the wet/dry.
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Andrew LMR God Offline 2006 SMS M.S. champion... more of a PB these days Posts: 1359 Camarillo	Re: 4.3 chevy Question Reply #7 - 07/26/09 at 12:03am What he said...
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