erratic timing?
Thread Starter
Instructor
Joined: Jun 2003
Posts: 158
Likes: 13
From: Arkansas
erratic timing?
what would my timing mark jump around a lot? mostly at idle. but a little at most ranges. I thought it may be due to the original dist being worn. I bought a Hei from ebay thinking it would eliminate it. but no real change other than it doesnt run as good as with points dist.
72 coupe 350 fresh original rebuild, bored .020.
500 lift roller cam
thanks
72 coupe 350 fresh original rebuild, bored .020.
500 lift roller cam
thanks
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Check the end play in the distributor. If the distributor shaft is jumping up and down the timing is changing. Also check to see where tie timing advance weights start to come in, the springs could bee too weak and letting the advance start at idle. Could also be an issue with the vacuum advance, unplug the hose from the dist can and watch to see if the timing is stable.
Last edited by '75; Nov 27, 2016 at 08:00 PM.
Thread Starter
Instructor
Joined: Jun 2003
Posts: 158
Likes: 13
From: Arkansas
USAFVeteran, i wondered that but i only have around 500 miles on the build
'75, i just checked shaft end play and its at .22 so ill address that with some shims. i also changed my springs and it seemed to help. I'll check locally for some tomorrow. thanks to both
'75, i just checked shaft end play and its at .22 so ill address that with some shims. i also changed my springs and it seemed to help. I'll check locally for some tomorrow. thanks to both
Racer
Joined: Feb 2016
Posts: 488
Likes: 43
From: Vancouver British Columbia
Just went through the exact same thing in my 1969. Timing jumping around at idle. My understanding is that unless all parts of your distributor are tight, this is the exact type of symptom you will see.
Lots of bushings and springs etc that just plain wear out.
But I am no expert,,, I just had my distributor rebuilt so I will be installing and testing it in the next few days and will let you know. Pete
Lots of bushings and springs etc that just plain wear out.
But I am no expert,,, I just had my distributor rebuilt so I will be installing and testing it in the next few days and will let you know. Pete
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
Just to eliminate the timing chain and gears, take the cap off the distributor so you can see the rotor. Turn the motor over for a few cranks on a ratchet. Mark the spot on the balancer, on the timing marks so you know where it is. Then turn the motor the opposite direct you just did, until the rotor moves. That will tell you the slack, if any in the chain. After that, you'll know if it's chain/gears or distributor.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Corvette & Porsche 911: How Two Icons Conquered the Last 25 Years
Joe Kucinski
2027 Chevrolet Silverado 1500 First Look: Everything You NEED to Know!
Michael S. Palmer
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
.22 is almost a quarter of an inch. Did you mean to put that measurement?
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
With .220 end play you must be getting a timing variation jump of 7 or 8 degrees. I don't think I've ever seen one with that much slack. At least it's a fairly easy fix.
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
Try a different light, or another plug wire.
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
Are you sure it's not the light, instead of the MSD? Where did you find this info, this is something I'd like to read myself? Thanks
Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
I was having problems with my MSD 6AL. Search the forum here or go to MSD site.
Let us know what you find!!!
Last edited by mikem350; Nov 28, 2016 at 11:19 AM.
Racer
Joined: Apr 2016
Posts: 493
Likes: 65
Yes MSD even states on their site that lights can false (especially the dial back ones) due to multiple sparks being generated at low RPMs. They sell a light that is supposed to work, I wonder who really makes it???
I was having problems with my MSD 6AL. Search the forum here or go to MSD site.
Let us know what you find!!!
I was having problems with my MSD 6AL. Search the forum here or go to MSD site.
Let us know what you find!!!
Thanks for the answer, I've never seen that. And no offense, but I don't really need to research it now. Unless mine starts having issues any way. But, I'll keep it in mind, thanks again