Frankenvette

My car is just not running right. I had it tuned on a dyno a few years ago and have made no adjustments since. However, the car has been running rough for awhile. I'm convinced its timing, but I have not checked yet. I can hear a popping sound in the exhaust system when I let up on the gas...kind of a pop...pop...pop sound. Anyone have any suggestion on what causes this?

nhlgopens

Check the timing and get it right before anything else... you may find that it's all that's needed.

checklst

Mine did the exact same thing timing solve the pop. As for why it would change over a period of a few years, some wear and also the gas mix at the refiner has changed.

mayberg

Is it possible that you're not getting good combustion on some cylinders (pull all the plugs to check?) and unburned gas is exploding in the exhaust pipes?

UKPaul

Popping in the exhaust on overrun can also be due to air leaks in the exhaust system or on the intake side. Have you checked for old, perished vacuum hoses causing a vacuum leak?

norvalwilhelm

Stock cars going into the corner pop and shoot flames out the exhaust. This is caused by carb idle adjustment, fuel is being sucked into the motor when letting off the throttle.

The Dude

Or a too-rich mixture at WOT.

PRNDL

I got popping out the exhaust when I let up on the gas whenever I had a leak in the exhaust system. Once I had a broken front pipe (it sounded louder then, in addition to the popping). Another time I had not made an airtight connection at the muffler. Not sure why a leak that far back in the exahaust system would still cause popping.... but it did.

Frankenvette

I do have small gasket leak at the header on the drivers side. Are you saying this could cause the popping?

wills670

if you have air injection a bad diverter valve will cause that problem.
it will be puting in cold air in system at the wrong time.

Frankenvette

No air injection.Iin fact, not a lick of emissions on this vette.

76REDSTINGER

yes

a leak in the exhaust WILL cause poping

i just fixed mine....bad header gaskets

R.

76REDSTINGER

yes

a leak in the exhaust WILL cause popping

i just fixed mine....bad header gaskets

R.

PRNDL

Yes, and so is 76REDSTINGER


Yes, and so is 76REDSTINGER

78pacer

I suspect a bad valve\valve spring...as metioned before, time to pull the plugs

UKPaul

A leak at the muffler connection will cause popping. I've got a very small leak in the connection between the exhaust & muffler on my bike & it causes major popping on the overrun. I quite like it, so haven't bothered fixing it
A badly seating valve can also cause it (damaged valve/set, weak/broken spring), but I'd check for exhaust/intake leaks first as these are usually the culprits. A compression test should find a problem with a badly seating valve.

Frankenvette

I have rebuilt Vortec heads, so I hope and think this is not the reason. I do have exhaust system leaks at the head/header and collector. I still think I have a timing issue as well but may not be related to the popping. Its always somthing with this car.

LakotasRose

Hey Jim!! That is why it's called ''Frankenvette''!

Frankenvette

Hello to you too. I hope all is well in Moorseville.