the engine wants to run after shutting key off...

[rogus]

I recently dropped a new 355 sbc into my 86 Elky. It hasn't seen the road yet and I'm still working on getting everything adjusted. I let the engine run till it warmed up and when I shut it off it tried to continue to run for a few seconds.

It uses an HEI and 670cfm Brawler carb, if that's of any help.

What generally causes this "run on" to occur? Is there a general list of possible fixes?

 

[69hurstolds]

Get an Olds. 🙂 Sorry, had to.

Run on as far as what? Dieseling? Or just running right along like the key was still on? Could be a misadjusted fuel system, ignition timing, or hot spots. Or somethng may not be getting the signal to cut off the primary ignition circuitry right away. How's the start switch adjustment?

 

[rogus]

sorry. not used to calling it dieseling. It's a new switch. Out of the 3 things you listed my guess is that it's a fuel supply problem. I need to adjust the carb still.

 

[69hurstolds]

Poor quality gas, large amounts of ignition advance also contributes to dieseling. Oh, and with all that other junk, if your idle speed is high it can be a contributing factor.

 

[Ernest]

One typical culprit is the primary butterflys are open too far overexposing the idle transfer slots adding additional fuel over the idle feed port also causing an overly rich condition, bad for sparkplugs and the cylinder walls.

When this happens, you have zero control of the idle mixture screws, this happens quite frequently when opening the primaries up to far(as 69hurstolds had mentioned) to acheive the desired idle RPM when using radical camshafts, in that instance, you have to ballance the intake air by opening up the secondaries just a tad so you dont overexpose the primary side.

Whats the total specs on the 355 engine?

 

[rogus]

One typical culprit is the primary butterflys are set too high over exposing the idle transfer slots adding additional fuel over the idle feed port.

When this happens, you have zero control of the idle mixture screws, this happens quite frequently when turning the primaries up to far(as 69hurstolds had mentioned) to get a decent idle rpm when using radical camshafts, in that instance, you have to ballance the intake air by opening up the secondaries just a tad so you dont overexpose the primary side.

Whats the total specs on the 355 engine?

Info is attached. It has a 670cfm Brawler carb, hei distributer, long tube headers...

 

[Ernest]

The good thing is that you are running with a GM factory roller block, but modified to run a mechanical fuel pump.

Everything else looks good... but from what i can barely read(sorry), the 212int/230exh camshaft should run comfortably @ 800rpm at idle with 14degree initial timing.

That 670 brawler should handle your engine without any problems, much like my holley 670 street avanger being used on my ZZ4 crate engine, it took me awhile to figure things out, but its running good atm.

 

[rogus]

The good thing is that you are running with a GM factory roller block, but modified to run a mechanical fuel pump.

Everything else looks good... but from what i can barely read(sorry), the 212int/230exh camshaft should run comfortably @ 800rpm at idle with 14degree initial timing.

That 670 brawler should handle your engine without any problems, much like my holley 670 street avanger being used on my ZZ4 crate engine, it took me awhile to figure things out, but it running good atm.

Thanks. I'm still relatively new at this.

 

[MrSony]

Back the idle speed down until it stops.
Then readjust mixture and timing if need be.

 

[spongbob]

Get it cool enough temperature wise then get it rich enough to idle down to 650 rpm or less if that dosnt fix it