hey my boyfriend and i own a a 67 chevy and i was just wondering if you guys could help with one little tiny problem i know i shouldnt be asking this but ive ran out of options i ask everyone and and cant get any answer that seems to work...

we just recently repalce a 307 in the truck we now have a 350 in it and for some unknown reason it want to keep running after you turn it off, weve never ran into a problem like this before and we need help, weve try everything from octane boost and a higher grade of gas, we thought it was in the timing but that dosent seem to be the problem at all, the octane boost work for like a day, so any ideas on what it could be?

just to let you know i have an oldsmobile dont take it out on me that i own a chevy too

 

I would look at timing first.

 

Do you mean dieseling (knocking and finally coughing itself out) or as in won't shut off at all?

Check:

idle speed and throttle plate opening

does it have a working anti-dieseling solenoid? (on driver front of carb throttle linkage- if it's not adjusted right, or if it stays extended all the time when switch is shut off, it can cause this)

timing

vacuum leaks

If it won't shut off at all and you have an HEI distributor, possible the HEI 12v power source is on a constant 12v instead of switched.

 

[quote=rocketraider;75469]Do you mean dieseling (knocking and finally coughing itself out) or as in won't shut off at all?

its defently dieseling... and i will check this things when i get home...and ill let you know

 

The easiest way to stop this (Not the correct way) is to shut it off while in gear before you put it in park.

 

here the thing about that its a three speed on the colum..
so any more ideas

 

What is the engine temp? Does it run hot? There may be excess carbon build up in the combustion chambers. That can stay hot and cause the run on situation. Back in the day, we would pull the air cleaner off, and while running the engine at around 2000 rpm, SLOWLY dribble water out of a bottle down the carb. Don't kill the motor because it will drag down. I thought my old boss was crazy the first time I saw that but it does seem to clean off the carbon. There are more fun ways to blow off the carbon too. Or try bumping the timing back a couple degrees. It's been a long time since I dealt with this problem.

 

I don't know about water boarding your engine but this stuff has been around for a long time.And many people swear by it.

http://www.seafoamsales.com/motorTuneUpTechGas.htm

 

Put a stronger return spring on the carb linkage.

 

thanks for all the advace but i got it run really goood now so thanks guys for all the help

 

Yeaaa I figured there would be some who thought I was crazy but I was sceptical too. I was a mechanic in the 80s and we would get the grandma cars with these problems and this was generally the first thing our tune up guy would do. These fossils would never get the cars up to operating temp or run it over 1500 rpm. Only going to church or the local store. Has anyone else heard of this?

 

I never poured water in the carb but used to use automatic transmission fluid. Talk about smoke out the tailpipes. You had to do it really slow but it worked pretty good. Been a long time since I have done that or remembered doing it.

 

I suppose with everything EFI now that problem has gone away. Just like kids nowadays never having the thrill of doing the infamous Key Bomb/shut off the key,pumping the accelerator pedal and turning the key back on when you are next to a jogger! You gotta teach kids how to drive a Carburetor like teaching them to drive a manual transmission.

 

It's the same deal...put the trans in high gear and let the clutch out and it will quit instantaneously...