how do I stop engine run on?

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screeminDemon

screeminDemon

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Now and then I get engine run on for a second or two after I shut down. It's really not a big deal, but I'm wondering what causes it, and what adjustment I need to stop it. Thanks for your help.

My engine:
360 bored 30 over with stock pistons
low cmpression, probably 8 or less
360 heads mildly ported and milled .015
summit cam 480 lift
eddy performer intake
thermoquad carb
headers
orange box elect ignition

I run pump gas 89 octane.
 
How hot does it run? If it's running 200 or above run on can be an issue. In that case you just need to get it running cooler. If the temp is ok what is the base timing set at? If you have it set to stock specs which is generally close to TDC you can advance it quite a bit for better low end performance and fuel mileage and it'll most likely help with the run on. If you advance it you have to make sure the total timing doesn't go over about 36-37 degrees or it may spark knock. If the total timing does go too high when you advance the initial timing to 14 you'll need to weld up the advance slots in the dist. to limit travel. If I were setting it up I'd set the base timing to about 14-15 degrees before TDC with 35-36 degrees total. I'd also replace the odd spring with a lighter unit so the advance comes in quicker. That's a pretty big cam for such low compression. Getting the timing right is critical to optimum performance.

Oh yeah what rpm do you have it idling at? If the idle speed is too high it may want to run on.
 
Oh yeah, why are you running 89 octane? I'd think 87 would be plenty with low compression and a perf. cam. If you run more octane than needed you can actually loose power because the higher the octane the slower it burns.
 
WHAT IS your timing setup?

My first guess is, idle too lean, not enough timing, and too much throttle, plus the TQ may be too lean and the throttle may be running so far open, it's out of the idle transfer area
 
67Dart273 said:
WHAT IS your timing setup?

My first guess is, idle too lean, not enough timing, and too much throttle, plus the TQ may be too lean and the throttle may be running so far open, it's out of the idle transfer area
Click to expand...


This one and Redfish

x2
 
This happens on my car if I run anything other than 94 octane gas.

I find shutting it off in gear stops it from running on.

It's just enough to load the engine preventing it from running on.
 
thanks for all your suggestions! I spent alot of time last fall getting the timing dialed in right where I like it, so I'm gonna try some other things first. It doesnt run hot. I have a 185 thermostat and thats about the temp it runs at. As for too lean - could be... I havent messed with the TQ at all since installation. But DemonSizzler set it up based on the specs of my engine and I've been very happy with it, so I dont want to mess with it yet either, unless all else fails.

I'm gonna try lowering the idle, as a few of you suggested. I've had it set kinda high for a manual trans. It sits about 1100. I leave it at that setting because I dont have a choke, and it helps me when I take off for work in the morning without taking the time to propperly warm up the car (I know thats probly not a good idea).
 
The timing being where "you" like it may not be where the engine wants it.

Most of the time run on is caused by not enough initial timing.
 
You can also think about installing an idle solenoid, which will keep your 1100 rpm idle until you turn off the key, then it will close the throttle blades and stops run-on.
 
I just caught the 1100 rpm idle. No reason for it to be that high with your camshaft and is helping to cause run-on . If you need it to warm up in the morning, find another method rather than to band-aid the no choke with excessive idle rpm.

That should idle in the 850 range without issue if initial is set properly.
 
X-5 on the idle speed.

I have to run around 1000 rpm with my big cam and it tends to run on on shut down.

Sometimes my idle is lower depending on engine temp, load, and your typical Holley temperament and the idle is lower when I shut down, and it never runs on then.

With four speed cars you can pop it into gear and pop the clutch to snuff out the run on rotation to save yourself the embarrassment of feeling like your car is a clunker.
 
cudaspaz said:
X-5 on the idle speed.


With four speed cars you can pop it into gear and pop the clutch to snuff out the run on rotation to save yourself the embarrassment of feeling like your car is a clunker.
Click to expand...

LOL! yes I do that when in public places. mopar pride always a factor.

I plan to lower the idle and re-check the timing in a couple days when this crazy seattle snow has passed. I drive the demon in rain fairly often but wont risk the snow
 
I fixed mine by shutting the engine off in drive or reverse. Just remember to put it into park when the engine has shut off!
 
airwoofer said:
I fixed mine by shutting the engine off in drive or reverse. Just remember to put it into park when the engine has shut off!
Click to expand...

So you really didn't fix it... :D

Ever get an initial timing number, it needs to be high with the cam you are running.
 
Gave back the good timing light with the turny timing dial I borrowed so the answer is no I didn't. The engine runs great as it is and it is no biggie to shut it down in gear.
 
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