Mercury Cougar Owners banner

1 - 9 of 9 Posts

·
Registered
Joined
·
114 Posts
Discussion Starter #1
Finally got my car ready enough to drive more frequent. (motor mounts). Now i have a popping sound coming from the carb when i accelerate. Took her on the highway and at 60 cruise all you hear is pop pop ppop popop. and a slight surge. at idle i can rev it hard and it will pop through the carb also. Any ideas? She starts fine. Has a Holly 600...edelbrock performer intake on a 351 w. Thanks in advance
 

·
Registered
Joined
·
418 Posts
Check the advance on your dist, you may have a slight leak in the vacc tube ( if its vacc advance) or you may need to adjust it.
you can also find the manual on the carb (if you dont have it) on edelbrocks page if you need to adjust it.
 

·
Registered
Joined
·
11,950 Posts
Agree - sounds like timing or vac leak - double check your wires for crossed/bad ones. So it doesn't do it just idling and reving it up I take it? Only under load - look at the advance plate in the dizzy as well.
 

·
Registered
Joined
·
7,552 Posts
+1 for the wires being out of order.. Have you done any recent work on the car? Is this a new condition?
 

·
Premium Member
Joined
·
13,577 Posts
Fingers crossed for wires incorrect. If all is in order and this did not happen "all of a sudden" after some work, a likely cause for this is a wiped out intake cam lobe which causes the lifter to pump up to compensate. The result is a "lift" profile with WAY too much duration = popping back through intake. Hope it is not that!

Regards,

Bob
 

·
Registered
Joined
·
11,950 Posts
I hope we don't have to go to dead valve either....
 

·
Premium Member
Joined
·
2,303 Posts
I was wondering if anyone would say that. It's exactly what is wrong with my car.
 

·
Registered
Joined
·
223 Posts
Fingers crossed for wires incorrect. If all is in order and this did not happen "all of a sudden" after some work, a likely cause for this is a wiped out intake cam lobe which causes the lifter to pump up to compensate. The result is a "lift" profile with WAY too much duration = popping back through intake. Hope it is not that!

Regards,

Bob
If the popping has a rhythm to it that increases frequency with engine RPM I'd bet its a wiped exhaust cam lobe not an intake lobe. Reason being the exhaust has no where to go but back through the intake valve when it opens. An exhaust valve train problem of any kind that causes the exhaust valve to only slightly open will not pop at idle but will pop when the RPM's or throttle angle are increased past a certain point. Depends on how much the exhaust valve opens verses how many CFM of air is getting into the affected cylinder. In most cases I have seen there is usually some audible valve train noise but I have seen a few cases without audible noise.

Bill
 

·
Registered
Joined
·
11,950 Posts
Unfortunately it's the oils that are offered that kill the cams in our cars.....they are no longer designed for flat tappet setups. You must add zinc (ZDDP) or run racing oils that already contain it or you will wipe one out in short order. If you rebuild it - you need to get religion on that, it's getting expensive and harder to find!
 
1 - 9 of 9 Posts
Top