My car currently has a Buick 455 from a '74 Riviera. It has iron heads, intake, and Q-Jet carb. When the weather changed it started to do a Chitty Chitty Bang Bang esque after-fire on the decel. Previously i could tune it out. But, now it cant be. I am guessing the the primary jets need to be increased in size. What do you guys think? Joel
My guess is vacuum leak (check all hoses) or exhaust leak at manifold. Draws fresh air in and combusts fuel with the engine braking causing the retarded timing situation? I think there's also a solenoid on the carb to hold the throttle at slightly off idle during decel.
It would be my guess that if we all guessed at it long enough that 90% of us would be wrong. Need more info......compression normal on all cylinders? Performance normal on acceleration? Any unusual sounds....ticking,clatter? A backfire is usually through a valve or excessive unburnt fuel that has nowhere to go. It is safe to say that it could be a lot of things that would make the same noise your hearing. Pull the spark plugs and check the compression before you spend any money on it.
Ive had issues with the carb base gasket leaking air. Caused all sorts of weird drivability problems.
Thanks guys! Hopefully I've found the issue. The nuts fell off of the passenger side header. I would have never checked before because it's exhhaust is usually loud. Hopefully this is the root of the issue.
