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: 2,364
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: 18,665
Likes: 2,564
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
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Melting Slicks
Joined: Dec 2009
Posts: 3,224
Likes: 652
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: 14,370
Likes: 6,364
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
Joined: May 2006
Posts: 18,665
Likes: 2,564
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
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.