edselflop

trim.o6ieSr.MOV

Hopefully the video is attached. The car seems to run just fine, but there is an inconsistent popping out the tailpipe at idle. i just replaced the intake and carb with a rebuilt 4100, but the popping was there when the old 2100 2-bbl carb and intake was on it. The points were replaced with a Pertronix unit (still running the old coil). I have also checked the exhaust manifolds and they appear to be tight as well. Any thoughts on what to look for?

Thanks!!

barnett468

leaks in the exhaust system.

leaking exhaust valve.

a compression test may help find the prob.

08'MustangDude

Popping can also be from too much gas in the exhaust, and once it's hot, it
ignites in the pipes. SO, you put a 4100 on it, which is almost twice the
that of the 2100, so if this only happens once the engine it hot, then
it's gas being ignited somewhere on exhaust. That carb is putting
too much fuel into the motor.

edselflop

The popping begins as soon as the cold engine is started-up, and doesn't get better or worse as the engine comes up to temp. Question: if the exhaust manifold bolts are all tight, would it just make sense to try new exhaust gaskets anyhow? I know that these particular gaskets did NOT have any of that copper gasket material used ... is that something I should also try?? I am running the stock cast iron manifolds ...... I can run a compression check, but will need to wait until the weekend.

Gun Jam

what about a hole in a muffler or pipe not at the manifold but down stream.

edselflop

OK, this is bugging me so I just ran a compression check and it showed: #1=100, #2=100, #3=90, #4=100, #5=95, #6=95, #7=90, #8=90. This was checked on a COLD engine.

Gun Jam

they are all really low but the difference is good.


so are you sure the muffler and/or pipes arent rusted through or leaking at all?

barnett468

what gauge did you use? cheap gauges can be off by up to 20 lbs. the good thing is that one is not substantially lower than the rest.

also, did you do it with the throttle fully open and turn the engine over at lest 4 times?

barnett468

"twice as much" means nothing in this instance. he stated it did the same thing with the 2100, plus the carb size is irrelevant at idle. the thing that is relevant is having the fuel mix screws properly adjusted.

08'MustangDude

I listened to the video, sorry, but towards the end is sounds like the drum beat to
"Hot for Teacher" - Van Halen...

Sounds like you got some air leaking past the the exhaust valves on the compression
stroke...

Also, do the compression test warm, so the rings are seated.