engine run-on
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
engine run-on
How do ya stop it? I use 93 octane gas. Initial timing is at 14 BTDC. Total mechanical advace = 36, no vacuum advance. I have an MSD 6AL box and installed the ballast resistor as per their instructions. The motor idles near 1000 RPM in neutral/park and 650 in drive, I can't go any lower.
Turning it off in gear seems to work, but would rather not have to do that. MSD suggested trying to turn off the motor with headlamps on (draw current) as a test to see if an in-line diode is needed, but it still runs on when I do this.
The L48 started running on a bit about a month before I yanked it out.
Any thoughts?
Thanks,
Turning it off in gear seems to work, but would rather not have to do that. MSD suggested trying to turn off the motor with headlamps on (draw current) as a test to see if an in-line diode is needed, but it still runs on when I do this.
The L48 started running on a bit about a month before I yanked it out.
Any thoughts?
Thanks,
Race Director
Joined: Oct 2000
Posts: 14,997
Likes: 79
From: central FL, near the beach.
i always shut mine off in gear, i wouldn't consider neutral. no run-on ever
But, i always joke that if i sold it, a new buyer couldn't drive it without written instructions and 3 days of training
But, i always joke that if i sold it, a new buyer couldn't drive it without written instructions and 3 days of training
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Is it a dieseling type of run-on? If so, you'll find that blipping the throttle after shut-down will get it to stop. This is one of the reasons that solenoids were fitted to carbs in the early '70's. Not only did they control idle speed but would pop the throttle open slightly to avoid after run at shut down. Using higher octane fuel should help too, although that's just a band-aid. Could also be due to carbon deposits/hot spots.
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Race Director
Joined: Oct 2000
Posts: 14,997
Likes: 79
From: central FL, near the beach.
but, let's say i had a tough customer who demanded this arcane feature.
I'd install an idle stop solinoid hooked to the neutral safety switch. wired to boost idle speed in gear and reduce it to 600 in neutral. And he'd pay plenty for it
I'd install an idle stop solinoid hooked to the neutral safety switch. wired to boost idle speed in gear and reduce it to 600 in neutral. And he'd pay plenty for it
Burning Brakes
Joined: Apr 2003
Posts: 844
Likes: 0
From: Central KY
Thoughts - Drop initial timing a bit (maybe to 10 degrees or less) and see if problem goes away. You can also put something in the fuel to clean up the chambers a bit... You also want to be sure the throttle blades are as closed as possible, lower idle RPM and check the idle mixture settings.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
water through the carb will clean up the chambers and the pistons, ATF also...don't flood the engine in it and do it with the throttle opened, the ATF will make some nice smoke also, perfect to annoy the neighbours 
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
Originally Posted by isosceles
How do ya stop it? I use 93 octane gas. Initial timing is at 14 BTDC. Total mechanical advace = 36, no vacuum advance. I have an MSD 6AL box and installed the ballast resistor as per their instructions. The motor idles near 1000 RPM in neutral/park and 650 in drive, I can't go any lower.
Turning it off in gear seems to work, but would rather not have to do that. MSD suggested trying to turn off the motor with headlamps on (draw current) as a test to see if an in-line diode is needed, but it still runs on when I do this.
The L48 started running on a bit about a month before I yanked it out.
Any thoughts?
Thanks,
Turning it off in gear seems to work, but would rather not have to do that. MSD suggested trying to turn off the motor with headlamps on (draw current) as a test to see if an in-line diode is needed, but it still runs on when I do this.
The L48 started running on a bit about a month before I yanked it out.
Any thoughts?
Thanks,
Also, a slight vacuum leak will force you to idle the engine higher to prevent stalling. You may want to look for old cracked hoses.
Hope this helps.
BigBlockk
Later.....
Burning Brakes
Joined: Nov 2004
Posts: 1,028
Likes: 0
From: San Antonio Texas
does it continue to run on now that you've un-installed the MSD ignition??? if so, sounds like dieseling after shutoff (pre-ignition). i had a 78 camaro (when they were new) with a 350 and quadrajet. it started doing this REAL BAD after a few years. even the Chevy dealers mechanics could never get it stopped. probably a bad dose of carbon build up in the engine from carb running rich for a long time. that raises compression dramatically and can cause this problem. try some of the suggested home remedies like Marvel Mystery Oil, etc. if that doesn't work and engine timing is correct and ignition system is in good working order then your probably looking at removing the heads at the very least and de-carbonizing the pistons.
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by Twin_Turbo
water through the carb will clean up the chambers and the pistons, ATF also...don't flood the engine in it and do it with the throttle opened, the ATF will make some nice smoke also, perfect to annoy the neighbours
yes, this is the same as dieseling. I still have the MSD box hooked up.
Matt; that device is exactly what I'm looking for and that customer would be my wife for when she drives my car.
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 3,128
Likes: 3
From: Deltona (son of Deland and DAYTONA) FL
Originally Posted by Matt Gruber
years ago, i did put a diode in my 61.
