Ignition problem? Rough idle, dies

M

Mac442

Not-quite-so-new-guy
Apr 25, 2020
48
18
Ocean County, NJ
About a week ago my 383 sbc started running like crap. It won’t idle unless foot is on gas, dies. Runs rough when holding gas. Gas smell really bad, it almost seems that it’s not igniting correctly.

all components of the engine have less than 1500 miles on them. Carb is a Holley 4150 750. I tuned it with vacuum gauge and it ran great about a month ago. Power valve is good.

Running MSD diet, 6AL box and blaster SS coil. when I tuned it and changed the advance springs I noticed the rotor looked a little whooped despite having so few miles on it I replaced it. After it started running rough I remember this and checked the cap and the carbon button was almost gone! I got a new cap today thinking that would fix my problem but no luck!

any thoughts! I’m thinking of replacing the coil and plugs next.

side note, when it initially start when cold it runs normal for about 10 seconds then the rough/missing starts.
 
MrSony

MrSony

Geezer
Nov 15, 2014
5,559
113
Des Moines, Iowa
Beefed up qjet time
:D
 
  • Agree
Reactions: Dayzedandkonfuzed
pontiacgp

pontiacgp

blank
Mar 31, 2006
27,784
113
Kitchener, Ontario
with a problem like that I would change the oil, it's polluted with gas. You need to be carefull with a carb that is dumping fuel, it will wash the oil off the cylinder walls and you can ruin the rings and bore.
 
M

Mac442

Not-quite-so-new-guy
Apr 25, 2020
48
18
Ocean County, NJ
with a problem like that I would change the oil, it's polluted with gas. You need to be carefull with a carb that is dumping fuel, it will wash the oil off the cylinder walls and you can ruin the rings and bore.
Thanks! I worried about this too. I’m going to take a look at the carb in the morning.
 
Clone TIE Pilot

Clone TIE Pilot

Royal Smart Person
Aug 14, 2011
2,233
113
Galaxy far far away
Most likely a vacuum leak. Lean exhaust smells much stronger than a rich exhaust. Lean mixtures also are hard to ignite and can mimic ignition issues.
 
  • Agree
Reactions: fleming442
M

Mac442

Not-quite-so-new-guy
Apr 25, 2020
48
18
Ocean County, NJ
Pulled the needles out of the carb this morning before work. A lot of junk in there! Looks like the O-rings are falling apart too.

8134D81C-21A5-4B87-9D55-A7111E5F1721.jpeg


looks like I’ll be going through the whole carb again. Weird that the O-ring disintegrated. Don’t have many miles on the carb at all.
 
GuysMonteSS

GuysMonteSS

Royal Smart Person
May 21, 2011
1,245
113
Kentville,Nova Scotia,Canada
Ethanol in the gas ??
Guy
 
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