running on

robert montvill · #1 (**permalink**) 06-01-2009, 08:26 AM

I have a 351/408 stroker windsor engine. It idles at about 950rpms.Sometimes when I shut it off, it runs on for about 2 0r 3 seconds. I run Exxon high test gas. Any help would be appreciated. thanks

Ron61 · #2 (**permalink**) 06-01-2009, 08:42 AM

Have you checked your timing? Also make sure that your carb, I am guessing that is what you have as you never said, isn't leaking fuel down into the hot cylinders after shut off. Also is the idle to high for your engine? Mine idles at 1100 and I have no problems at all with run on, but I did have with one car and found out that the idle had crept up and was about 200 RPM to high. I lowered it and no more problems. Hope this helps, and I am sure that some of the real knowledgeable people will give you some good ideas on what to look for.

Ron

Zoom This · #3 (**permalink**) 06-01-2009, 09:03 AM

Run on is pretty common on many carbureted hi-perf motors. You can solve it several ways. Turn down your idle speed as suggested by Ron. Put your car in 4th gear at idle and let out the clutch until tach indicates a lower rpm then turn off the ignition. Or, you can install a solenoid on your carb throttle linkage that can be set to allow proper idle speed when the motor is running, but as soon as you turn off the ignition it allows the idle speed setting to drop to zero and closes the throttle plates entirely.

Bill

blykins · #4 (**permalink**) 06-01-2009, 09:07 AM

What's your initial timing set at? You can try giving it a couple more degrees, then turn your idle back down to compensate.

You can also adjust your mixture so that it's a little richer than before. This will sometimes buy you a little bit of lee-way and you can turn the idle speed screw down a little bit to compensate.

Last but not least....does it need to idle that high?

RicManSr · #5 (**permalink**) 06-01-2009, 09:17 AM

What kind of build is it? Does your Cooling fan have a relay in it? Mine did the same thing till i put a relay on the radi. fan. The fan was back feeding the ignition & causeing a run on. Installed a relay for the fan solved my problem.

robert montvill · #6 (**permalink**) 06-01-2009, 09:52 AM

thanks guys for all of the feedback.Here are the answers to the questions that were asked.The engine is a 408 stroker with a high performance cam.It has a new holley 750 carb.I have it idling at that speed just to have the engine running fairly smooth.Once again,thanks to everyone.

STL Mark · #7 (**permalink**) 06-01-2009, 11:44 AM

I have the same problem. I'm having a solenoid put on this week.

rokndad · #8 (**permalink**) 06-01-2009, 01:05 PM

When I had the 4bbl on my car, it did the same thing initially. I reset the idle to 800-850 and I have a pretty lumpy cam in it and it initially didn't sound right idling at that speed. I always thought it was going to stall, but it didn't so I left it there. Once the idle speed was down, it quit running on. I later bumped up the idle slightly and added a can of octane booster to the fuel. No run on.