440 popping in exhaust at idle

[Rchab]

Heading pretty much explains it, it does shake the car a little but it's less of an actual pop and more feels like extra air coming out of the exhaust. I have developed an exhaust leak right after my cutouts that I believe is the culprit for lean popping (actual popping unlike this idle pop) on decel as I'm driving, could this be causing the idle pop as well? The only caveat to that is it still pops and doesn't change repetition when I open the cutouts. I have attached a video as well to further explain

 

[BeepBeepRR]

Possible burnt valve. At higher RPM's probably not showing as a problem. That's my guess.

 

[icetech]

Pull plug wires from the cap one at a time and see which cyl the noise goes away when pulled... check the plug (and/or swap a plug from another cyl) and go from there....

 

[Fran Blacker]

Compression check while plug is out.

 

[Skatpak]

it could be a burnt valve, but it sounds like a lean pop to me, Ive had this happen not only to me but to cars brought to me for this exact reason, and in most of the cases (not all) it turned out to be a fuel problem. because the Idle circuit is separate from the main circuit, it can be lean at idle and fine at off idle. Try to adjust the idle mixture screws to see if that helps. Its quick and easy and does not cost a thing. I would check that first.

 

[Rchab]

it could be a burnt valve, but it sounds like a lean pop to me, Ive had this happen not only to me but to cars brought to me for this exact reason, and in most of the cases (not all) it turned out to be a fuel problem. because the Idle circuit is separate from the main circuit, it can be lean at idle and fine at off idle. Try to adjust the idle mixture screws to see if that helps. Its quick and easy and does not cost a thing. I would check that first.

I forgot to mention it has a Holley sniper system on it so no carb. That being said my afr is 13-14 at idle if i remember correctly.

 

[Dave6T4]

Too much initial timing?

 

[Geoff 2]

If dual exh, does it pop both sides? That narrows it down. I would be looking at burned exh valve, incorrect lifter adjustment or wiped cam lobe.

 

[steve340]

I think start with a compression check.

 

[Rchab]

If dual exh, does it pop both sides? That narrows it down. I would be looking at burned exh valve, incorrect lifter adjustment or wiped cam lobe.

It's left bank (drivers side if I'm thinking wrong) I just put a new cam in it but it also doesn't seem to happen when I'm off idle so I don't think I wiped a lobe? I'll be able to start looking into it here in the next couple days.

 

[BeepBeepRR]

A compression test would tell you more.

 

[mala]

Sparkplugg wire #5 and #7 cross or to close together?

 

[Griff]

What kind of Alternator (year and single or dual feed) and what kind of voltage regulator?

Mr. Dadsbee solved my problem a few weeks ago. Mine was more of a banging at idle in my 440 Roadrunner. I had a 1969 single wire alternator and a post 70' voltage regulator. They weren't talking well at idle. I changed to the newer PowerMaster single wire alternator (w/internal regulator) and pulled the one off the fire wall and bingo! No more banging out exhaust.

 

[beanhead]

The first easy test would be to connect a vacuum gauge to a full manifold source and watch how the needle acts. Not a 100% guaranteed diagnosis but can indicate several possible conditions and help narrow it down quicker. Post a clear video if you aren't sure how to interpret the gauge behavior.