Engine question

[Robs71Nova]

HI all. There seem to be alot of mechanic types on this forum so I decided to post this question here. As of about a week ago my Nova has been running very rough. When I put it in gear and go down the street there is alot of popping coming out of the exhaust, almost like a bunch os small backfires. I have been told that a) Something is messing up with one of my valves b) the timing may be off and c) the carb, etc. needs to be retuned. Do any of you have any suggestions? I havent had the oppurtunity to actually tear into it yet, but I plan on doing it tomorrow and would like a few opinions before I start. Any info would be appreciated.

Thanks
Rob

[Dan_in_WA]

Originally Posted by Robs71Nova

When I put it in gear and go down the street there is alot of popping coming out of the exhaust, almost like a bunch os small backfires.

They're probably right; I'd like to add that leaky headers can do the same thing if you're slowing down against engine compression.

Exhaust leaks would just be something to keep an eye out for.

[ridge_runner]

yea sounds like timing to me

[89IROC&RS]

wow, there are alot of things that could be,
what kind of choke are you running on the carb?
new timing chain when you put it together?
what size cam?
compression?
headers?
have you checked for corrosion inside the distributor cap?
new ignition coil?
id say it sounds like ignition to me. almost like a dying coil. but id have to test it to be sure.

[Genopsyde]

i agree with 89iroc.

[Robs71Nova]

Im thinking it is the coil too, but its not making any sense. I fried an Accel coil about a month ago and replaced it with a 50k volt GM coil, so the coil only has MAYBE 15 hours of run time on it. IM thinking of getting rid of the MSD box because I dont think its practical for everyday use. As for your questions its an electric choke on the carb, a comp cams double roller timing chain, Cam is a 500 lift edelbrock cam with a 232 int/234exh duration compression im not sure, the distributor cap and all were replaced roughly 6 months ago, Yes it has headers, and the ignition coil is about a month old. Thanks for your help

Rob

[89IROC&RS]

ok, if youve already fried an accel coil, thats where i would look. very likely you have some sort of wiring problem that is either on the power or ground side of that circuit that is shorting, or creating too much current draw, and frying the coil. very possibly the MSD box. i come to that conclusion as the rest of your setup sounds pretty mild as far as a street/strip small block, so i wouldnt say you are damaging anything there. i would get a new ignition box and coil, and see if that fixes it.

[406Elcamino]

My friends race car did that and it was a bad plug. He had just put in a new set of "champions" ha ha and a week later it started doing that. We put the old Autolites in and it quit doing it. Easy way to check which cylinder it is is to spray a little water onto the header tubes when its running and warming up. Not firing=cold header tube.