Popping sound in headers

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Wondering if anyone can tell whether or not I have a problem here. 340 w/Hooker comp headers makes a popping sound like small backfiring in the headers (or maybe a bit further down around the collectors, hard to tell) while idling before it is warmed up. It's pretty random and not frequent, maybe evry 20-30 seconds or so you'll hear a muffled "pop" type sound. Goes away after warmed up. Unknown cam.

What could be causing this, and do you think it is a problem I should look further into? Car seems to run fine, no other problems noted.

Any advice welcome, tks...

Paul
 
When the engine isn't warmed up it is usually running rich because of the choke. Also might be mis-firing once in a while for the same reason. Both of these can cause some unburned fuel to enter the exhaust. If you have a leak in the exhaust system, like where the header connects to the head or at a collector gasket, it can let air enter the system. This air can mix with the unburned fuel in the exhaust and cause it to explode. Result is a popping sound in the exhaust. I've often noticed this, particularly when the car is slowing under compression, like when you have just let off of the gas. This MIGHT be the cause of your problem. I'm really "old school" & not up on the latest technology. Somebody else here might have other ideas.


:burnout:
 
I'm pretty sure the exhaust is tight. I re-did it from the collectors back myself and cannot detect any leaks at the header flange gaskets. It has a manual choke which I normally release completely 5-10 secs after starting. The motor was allegedly rebuilt sometime shortly before I bought it. That is why I mentioned "unknown cam," because I was wondering if this condition might indicate the presence of a non-stock cam of some type which might exhibit this behavior "normally," so to speak.
 
You could be right about no exhaust leaks. The gaskets that are available now are a lot better than they were 30 years ago. Seemed like we could never keep header gaskets sealed, they were always burning through.
If you're releasing the choke as soon as you say then it's very possible that the engine is just mis-firing because it's running lean when it's cold. If everything smooths out after it's warm there's probably not a problem. Does the car have an automatic or a manual trans? If it's an automatic trans and it idles smoothly when warmed up & in gear it probably has a pretty mild cam. This is based on what I know of cams from MANY years ago. Cam science has advanced an unbelievable amount since the last time I messed with a serious street motor (Hopefully I'll start "messing" again in the near future).


:burnout:
 
It is a 4sp manual. Suppose I'll get the timimg light out and check the plugs just to meake sure everything looks good on the ignition side. It seems to run really well, though. Pulls strong all the way up to 6k rpm. That is the only reason I have not checked any of that stuff yet. I did pull one plug as soon as I got it home the first time and it looked fine.
 
Yes, it is the best starting car we have - fires up on the 1st crank every time. I mean it doesn't even crank, just flip the key and bam - it's running.
 
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