I've got a bored out 327 with stock cam, Q-jet on a stock manifold, stock distributor and coil, and cyclone headers. It was partially restored in the 1980's but has sat a lot recently due to job, family, and lack of dinero. I've have recently rejuvenated the restoration and have it running on the weekends. I have noticed a little irregularity in exhaust sound from the right bank and there seems to be some negative pressure at the right tail pipe. This side also has a significant backfire on decelaration at both high and low rpm's. Vaccum pressure gauge reading at the intake is 22 at an idle but has small regular drops to 17 or so. Think this is a sticky exhaust valve or similar problem. I do need to have the carb reworked, ignition and plugs repaced to eliminate them as a cause. Any other suggestions, ideas, or advice before I pull the heads?

Brian

Sure sounds like a bad valve.I would do a compression,and leakdown on that side.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

by back fire do you mean in the exaust pipe or through the intake.

exaust back fire is caused by a leak in the exaust system or a bad fireing cylender and un burned fuel geting into the exaust and igniting from the other hot exaust gas's.

intake back fire can be caused by a vacuum leak, timing problem, valve not seating, lean A/F ratieo, dirty carb, cam lobe's that are worn or flat, bad lifter.

hope this help's ya out! i would sugjest you do a good tune up and set the timing and clean out the carb or rebuild it and see how it dose. if it is still there look for a vacuum leak or exaust leak...good luck!

[This message has been edited by ilbl8 (edited 05-08-2001).]

ilbl8:

It's backfiring through the exhaust. I've got plans to pressure test the cylinders on that side as well as do a good general tune up. Then we will see were we stand. Thanks for all the info.

Brian