1976 Other Chrysler Models backfire

1976 CHRYSLER
10,000 MILES • V8 • 2WD • AUTOMATIC
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KEITH.NICKASON
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76 winnebago 440-3 therma quad

under high vacuum (throttle closed, down hill, 80km/h) exhaust backfire. timing on, carb rebuilt, heads rebuilt, full tune up, no intake or exhaust leaks. runs good under all other conditions. could i have weak valve springs or excessive valve guide. i'm stumped
Mar 4, 2010 at 8:05 PM
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HMAC300
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I think what you are hearing is low backpressure coming from the engine. A backfire would be loud, very loud. If it is a back fire it may be a small hole in teh exaust or coming off the exaust manifold. Like the heat riser as those weren't the best ones around. As they got closer to 1977 they starte haveing mufflers break on the inside. If you think it may be that, just hit it with a gloved hand with the enigne off and if you hear rattling the muffler isn't any good. It would also really flatten out around 50 mph. But you can put a vacuum guage on the intake manifold and if you are running low vacuum that is another indicator of a bad muffler.... 15" is low at idle
Mar 8, 2010 at 9:35 PM
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