Engine pop at gear change

Posted By: 65racer

Engine pop at gear change - 07/03/11 10:05 PM

Just had this problem rear it's ugly head this
weekend, when I make a pass in the car, just when
it is time for the air shifter to shift the engine
will pop 1 time right at the gear change, I have checked
everything over and cannot find anything wrong, it
was fine last weekend, and has just started doing this
someone point me in the right direction, I have a strong
suspicion of what it is, but I keep telling myself, that
is not the problem, so let's hear some of you guy's
theory on what I should be looking for.

Thanks
Dave

Posted By: Crizila

Re: Engine pop at gear change - 07/03/11 10:26 PM

Did you try shifting at a lower RPM to see if it goes away? The pop is usually unburned fuel lighting in the headers. Valve float will cause it. Also a weak ignition - are you supplying enough voltage to the ignition at speed?

Posted By: Cab_Burge

Re: Engine pop at gear change - 07/03/11 11:23 PM

Quote:

Did you try shifting at a lower RPM to see if it goes away? The pop is usually unburned fuel lighting in the headers. Valve float will cause it. Also a weak ignition - are you supplying enough voltage to the ignition at speed?

Valve float will end up seperating the valve heads from the stems

Is it popping back through the exhaust or intake? What RPM are you shifting it at and what RPM does it cross the finish line at

Try shifting it lower first and then go from there

Posted By: JACK1440

Re: Engine pop at gear change - 07/04/11 01:24 AM

we had this problem several years ago. ended up being a broken valve spring. checkem' out.

Posted By: Demon340GSS

Re: Engine pop at gear change - 07/15/11 12:22 AM

I had this problem with a 383 with 11.5 to 1's and fogger NOS set up plumbed into each runner and we installed in a 1971 demon 340 car, (factory 340 car) with hooker fenderwell headers and Direct Connection hydraulic bumpstick and a low profile offy intake 2x 4 set up with holley 650DPs mounted sideways on adapter plates that all fit under the stock dual scooped factory hood...
At first it ran like a raped ape and then it started to "happen" after we had about 90 runs on it..
We took it on the street and it started to find out what it was as it get's worse trying to find the issue...
It drove me nuts having not had it happen before and it turned out to be the valve springs!
I got one of those valve spring compressor's that allowed me to do it while motor was still in the car and one by one I changed out each valve spring with new ones that moparts sold as compatable and I used a small air compressor to keep the valve up in the head ( still I spun each piston to the top of the cylinder just in case I lost the valve so that it could not drop out of reach).
It never did it again after that.
Before this I had checked everything from my msd all the way to my tach as possible culprit's... Only to turn out it was the valve springs going away..
Grant Eaton 386-561-1181

Posted By: cgall

Re: Engine pop at gear change - 07/15/11 12:55 AM

Dave, an exhaust gasket leak or a cracked header pipe can cause that, too. If it pops loud after you let off, that is usually the culprit.

And congrats on your win last week, I wasn't able to get on and say anything earlier.

Posted By: 65racer

Re: Engine pop at gear change - 07/15/11 03:13 AM

Found the problem. and corrected it, and
it ran flawless last weekend, it was something I
did, that caused the problem, I had done some rewiring,
for something I was working on to try to do something
different, and I guess the car didn't like
what I did it, so I rectified the problem, and it fixed
it right up.

Dave