Running Issues
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Cross-Country
Joined: Mar 2016
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Running Issues
I have a 1976 highboy with a 360 in it and it runs really rich but I have tried adjusting the carburetor and if I go on the lean side it doesnt want to start. Also I have heard some pinging at the higher rpms, I was told this could be detonation occurring and would like to know how to fix this myself, because I dont really have the funds and would like to learn. The carburetor is a demon 4bbl 625cm. I also have the msd coil and mallory ignition. spark plugs and wires were new maybe a month or 2 ago.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Have you adjusted the mixture screws using a vacuum gauge?
Correct gap on the plugs?
Pinging at higher RPMs is an indication of too much timing and/or vacuum advance.
Are you running the stock DSII distributor? I think 76 was the first year for 'em. The reason I ask is that the vacuum advance can on these bad boys is adjustable.
Correct gap on the plugs?
Pinging at higher RPMs is an indication of too much timing and/or vacuum advance.
Are you running the stock DSII distributor? I think 76 was the first year for 'em. The reason I ask is that the vacuum advance can on these bad boys is adjustable.
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Cross-Country
Joined: Mar 2016
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I am not using the stock distributor I have tried adjusting the the fuel mixture screws and it should need to be leaned out but when I lean it out it does not want to start in the morning/it is really hard to start and doesnt run right.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Well now....see those questions in post #2? They are questions...they're particular questions for a reason, and they have the little "?" at the end. Without you answering the questions asked we don't know with what we're dealing. Just stating the same problems again will not help us diagnose the illness. It's like asking, "Why won't my vehicle start?"
I can't speak for the others on this site but I flunked mind-reading class in the second grade.
So, again...Have you adjusted the carb's mixture screws using a vacuum gauge?
Are the plugs gapped correctly? Pull a couple plugs and read 'em. What do they tell you?
What distributor are you using? The MSD one, no?
Does it have a vacuum advance can on it?
What's the timing set at?
So you have a Holley Demon 4v carb....when she starts, does the exhaust smell very "rich" such that it makes you eyes water?
I can't speak for the others on this site but I flunked mind-reading class in the second grade.
So, again...Have you adjusted the carb's mixture screws using a vacuum gauge?
Are the plugs gapped correctly? Pull a couple plugs and read 'em. What do they tell you?
What distributor are you using? The MSD one, no?
Does it have a vacuum advance can on it?
What's the timing set at?
So you have a Holley Demon 4v carb....when she starts, does the exhaust smell very "rich" such that it makes you eyes water?
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Cross-Country
Joined: Mar 2016
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Have you adjusted the mixture screws using a vacuum gauge?
I have tried adjusting the mixture as I stated before, I tried to lean them out because it smelled rich and it would not want to start in the mornings.
Correct gap on the plugs?
I have not checked the gap on the plugs nor do I know how to do this
Are you running the stock DSII distributor? I think 76 was the first year for 'em. The reason I ask is that the vacuum advance can on these bad boys is adjustable.
No I am using the msd one and it has the vacuum advance can on it.
I dont know what the timing is set at. I have the demon brand street demon 4v carburetor that is a 625 cfm carb.
I have tried adjusting the mixture as I stated before, I tried to lean them out because it smelled rich and it would not want to start in the mornings.
Correct gap on the plugs?
I have not checked the gap on the plugs nor do I know how to do this
Are you running the stock DSII distributor? I think 76 was the first year for 'em. The reason I ask is that the vacuum advance can on these bad boys is adjustable.
No I am using the msd one and it has the vacuum advance can on it.
I dont know what the timing is set at. I have the demon brand street demon 4v carburetor that is a 625 cfm carb.
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Yes, you've stated 3 times that you've tried adjusting the mixture.....but have you tried doing it with a vacuum gauge?
If you don't know how, just ask!
Plug gap/reading plugs....we'll get that in a bit.
Let's try this: On the carb, and while the engine is running, slowly turn one mixture screw in....not such that they're "cranked" in, but so that they're just lightly bottomed out.
Is she still running or did she croak? Answer, please.
If she's still running, do the same to the other mixture screw...... let us know the results, please?
If you don't know how, just ask!
Plug gap/reading plugs....we'll get that in a bit.
Let's try this: On the carb, and while the engine is running, slowly turn one mixture screw in....not such that they're "cranked" in, but so that they're just lightly bottomed out.
Is she still running or did she croak? Answer, please.
If she's still running, do the same to the other mixture screw...... let us know the results, please?
Senior User
Joined: Oct 2014
Posts: 130
Likes: 1
From: Pilot Mound, Iowa
"Yes, you've stated 3 times that you've tried adjusting the mixture.....but have you tried doing it with a vacuum gauge?"
Without a vacuum gauge your just guessing or pissin in the wind. Neither works very well. FWIW I have one mounted in the engine compartment and in the cab.
Jeff
Without a vacuum gauge your just guessing or pissin in the wind. Neither works very well. FWIW I have one mounted in the engine compartment and in the cab.
Jeff
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Cross-Country
Joined: Mar 2016
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I have a vacuum gage but have not had time to do anything with the carburetor today I will check when I get home and let you know sometime tonight. Also Sometimes after start up if it idles in drive it will sometimes die.
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