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popping through tailpipe


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peggyfran1
User

Jan 12, 2010, 12:27 AM

Post #1 of 5 (2723 views)
popping through tailpipe Sign In

1985 gmc pickup 350 with quadrojet.started popping like choke was sticking.put on rebuilt carb and new dist cap and rotor. not much change. still pops some and wants to die when put in gear unless you stay on the gas.just started this when it got real cold. thanks , frank


steve01832
Veteran
steve01832 profile image

Jan 12, 2010, 6:21 PM

Post #2 of 5 (2706 views)
Re: popping through tailpipe Sign In

Hi Frank. You may want to start with a compression test. You may have a valve problem, or a jumped timing chain. Please post back with the readings of the cylinders. You really want to watch the guage on the first puff. When you crank the engine, the needle will pump up. You should get over 50 psi on the first puff. By the 3rd puff, compression should be around 140 psi, if my memory serves me correctly.

Steve


john.mahoney77
New User

Jan 13, 2010, 5:56 PM

Post #3 of 5 (2697 views)
Re: popping through tailpipe Sign In

probly the timing chain


peggyfran1
User

Jan 14, 2010, 5:49 PM

Post #4 of 5 (2678 views)
Re: popping through tailpipe Sign In

whats the easiest way to find out if it jumped time,if there is one ,rather than tearing it down.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jan 14, 2010, 6:16 PM

Post #5 of 5 (2676 views)
Re: popping through tailpipe Sign In

One way is to set timing marks to zero by turning crankshaft bolt in one direction then count the degrees it moves turning the other way until distributor rotor moves. More than 5-6 degrees is trouble. If original chain the nylon cam gears don't age well with both age and miles too. Vacuum testing and compression testing could also be helpful.

By the time you have dug in and are looking at the thing strongly consider a new one while there! Cheap parts for the time it takes.

Some will run better for a moment if timing is advanced but take all info in for diagnosing,

T







 
 
 






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