Blowpack, Pop sound, not float (Full Version)

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Blowpack, Pop sound, not float

  

David09sp -> Blowpack, Pop sound, not float (5/9/2008 10:48:12 PM)

So seems as though another problem as pretruded as I am now working on performance. In idle the car every 15 seconds makes a pop out of the tail pipes, and this pop includes a gas mixture spraying from the tail pipes. Seems to only happen in idle or low throttle. I opened the carb to check the float and it seems fine, made sure the carb was tightly on and it was. The pop is random in sets, that it might happen twice in a couple seconds or once every 30 seconds.

  
Scott H. -> RE: Blowpack, Pop sound, not float (5/9/2008 11:21:56 PM)

Most common issue would be idle circuit too rich.  This could be caused by poor atomization (which causes puddling in the intake), or just too rich of a mixture. 
It could also be caused by an egr valve that has been disconnected, or an air injection system that has been bypassed, or a points style distributor with incorrect dwell... or a combination of the above.  
Is the "gas mixture spitting from the tail pipe" actually gas, or is it just condensed moisture, with a bit of a gaseous smell?  
I'd toss a vacuum gauge on and see what the reading is.  With a stock cam at less than 2K' above sea level, it should be 18-20"Hg.  Low, and steady reading would indicate a rich mixture-retarded timing issue. 
If I understand your post correctly, the intermittent popping is most likely caused by the exhaust manifolds running hot enough to cause the unburnt gass exiting the exhaust valve to "burn quickly" in the exhaust manifold.  So you want to reduce the amount of unburned gas that gets into the exhaust manifold by increasing the efficiency of the burn.  This will also decrease the exhaust manifold temperature.
Hth,  

  

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