Timing ?
Race Director
Joined: Sep 2005
Posts: 18,640
Likes: 121
From: Farragut,TN
what octane fuel and what is your idle speed? also what year is your car? And how are you trying to check timing? Do you have the vaccum line to the dist disconnected? in the old days When the timing was right on at about 30 in high gear at wot you would hear a slight ping
Last edited by 694speed350; Apr 26, 2016 at 08:22 PM.
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 2,369
Likes: 103
From: Centerville Louisiana
Just wondering on my question. I always disconnect and plug vacuum line to advance. 91 or 93 when I can get it. Just I've always just set my timing at idle never checked it at 3K. So my experince has always been at idle setting. Now I'm learning new tricks
Instructor
Joined: Apr 2016
Posts: 104
Likes: 7
From: Denver Colorado
A rich idle mixture combined with a fast idle speed will result in "run on".
Race Director
Joined: May 2006
Posts: 18,733
Likes: 2,582
you aren't telling us the complete story of what you are doing. It sounds like you are trying to set total mechanical advance to some number at 3k and are ending up with initial timing be higher than 12 BTDC. There is nothing wrong with that. If your idle speed is too high adjust the carburetor.
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
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Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
Except I set my total timing at about 35 degrees all in by 3000 rpm. The exact number depends on the details of the engine - heads, compression, etc.
Advanced
Joined: Jun 2015
Posts: 63
Likes: 7
From: Canberra ACT
Recent story, might not help OP but the question was pretty vague anyway so here goes.
I had run on (or dieseling) start to occur over the past few months so I know I had to check it. Got a timing light and found my idle was at around 12, should have been 6-8.
Also turns out my distributor hold down bolt was slightly loose so I could actually rotate the distributor by hand with enough effort. That explains why the car went from well tuned to rough. I followed the hood tuning guidance for my 75 and set the idle timing back to 6ish, adjusted fuel/air mix with vacuum gauge and it is running SOOO much better.
I haven't even checked total timing, perhaps I should, but setting the idle to where it should be has made all the differences. Also, no run on.
I had run on (or dieseling) start to occur over the past few months so I know I had to check it. Got a timing light and found my idle was at around 12, should have been 6-8.
Also turns out my distributor hold down bolt was slightly loose so I could actually rotate the distributor by hand with enough effort. That explains why the car went from well tuned to rough. I followed the hood tuning guidance for my 75 and set the idle timing back to 6ish, adjusted fuel/air mix with vacuum gauge and it is running SOOO much better.
I haven't even checked total timing, perhaps I should, but setting the idle to where it should be has made all the differences. Also, no run on.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Initial timing has no effect whatsoever on run-on after shutdown. The ignition is "off" at shutdown, so there is no spark, and no effect from whatever the timing is set at. Run-on after shutdown is a function of the carb's throttle plate opening and engine rpm at shut-down. For best performance, total timing should be set to 36 (if stock heads are used), with initial timing in the mid-teens.
Lars
Lars
Race Director
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Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Run on may occur if using a multi spark CD ignition. MSD supplied a diode with my 6530 box to help prevent run on when the key is turned off.