OKay, this is a weird one.
Have a 396/350 with a Holley 750....the ONLY way the engine will shut off w/o knockin' and choking to death is if the A/C is on!
http://www.chevelles.com/forum/confused.gif

Anyone have any idea why that is???

She is running rich, need to work on that carb, but still. Weird weird.

Is as bad as the last thing on my car, seems the guy who had it before me wired the lights to the ignition...only way to shut the car off was to turn off the lights.

Did he tell me that? OH NO!!! http://www.chevelles.com/forum/frown.gif

Sheesh, took me forever to find that one!
Tho' everyone at the car shows thought ti was real cool that my "Shevelle" kept running while I ahd the keys in my hand!

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My Dream - Buttercup (http://www.chevelles.com/showroom/butercup.jpg)

1970 Chevelle SS 396 350
2001 Chevy Silverado 4x4 Z71 350 Vortec
Team Chevelle #0796
ACES #05033
Late Great Chevys #162426
Real Women don't have hot flashes, they have power surges.

Maybe if you lean the carb idle circuit out a bit it will quit deiseling...Also make sure the choke is not partly on when warm...
Just a guess....

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Ron Cook TC Gold #1276 ___ ACES #5136
1969 300 Deluxe HTSS396 (http://www.chevelles.com/showroom/bow_tied4.jpg) The L35-325HP 396cid (http://www.chevelles.com/showroom/bow_tied3.jpg) 69 Memory Lane (http://www.chevelles.com/showroom/bow_tied.jpg) 1971 Malibu 2DR HT (http://www.chevelles.com/showroom/bow_tied_71Malibu.jpg)
CanAm Chevelle Club (http://www.canamchevelles.com)

Sometimes, if your idle is set too high, your engine will diesel for a while upon turning off the key.

It's probably dieseling because the throttle blades are open too far at idle, even if idle speed is about right. The throttle blades are probably open too far because of a separate problem. Could be with your carb too rich or too lean, timing not correct, vacuum leak, ignition problems, etc. If you find and correct the problem your idle speed will probably go too high, causing you to adjust it down, closing the throttle plates some and probably eliminating the dieseling.

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von '69 300 Dlx SS TC #15 ACES #1575
My '69 SS (http://mywebpage.netscape.com/jerryacheson/vons69.html)

Be sure you're running premium fuel. I've had cars that would "run-on" with regular in the tank, but shut off perfectly with premium.

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Bob Von Kaenel
70 SS 54k orig miles
My car. (http://www.chevelles.com/showroom/barista70front.jpg)
The red interior. (http://www.chevelles.com/showroom/barista70interior2.jpg)
The engine. (http://www.chevelles.com/showroom/barista70engine.jpg)
Hood trim. (http://www.chevelles.com/showroom/baristasgirls.jpg)

With a Holley carb I would check for a blown power valve in the carb, if it has backfired ever with the Holley, replace the power valve. This would cause rich condition which the last owner may have tryed to mask with a high idle, that is usually why an engine runs on. GM also originally installed an idle solnoid to rasie the idle when the A/C is on, if it was removed in the switch to the 750 the idle would needed to be higher to keep the engine running at idle with the A/C on. I would also check the timing, with about 10 to 1 compression factory, even factory timing specs can be agressive with today's joke called gas. Just somethings to check, good luck.

As others have said, a timing/idle adjustment is needed. When you advance the timing the idle/engine speed will increase. Back the idle, at the carb down as you advance the timing. If you advance the timing too far you will create spark knock and will have to back it off. You will have to find a happy medium. The goal here is to get the throttle plates shut, or close to being shut, at idle.

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Ed C.
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70SS 396/350 4speed
70 LS6 4speed under resto.
00 C5 6speed

Sounds weird to me. Does it have an AC solenoid? I think they're supposed to make it idle a bit higher, which is strange since that's when it doesn't run on when you turn it off. I'd check the idle screw and cam to see if it's where it should be.

I think Von is right on the money. You can actually set the timing so that you have to open the throttle too far at idle in order to get it to idle at the proper speed. You might try a little more initial advance and back off the idle speed screw.

Thanks so much guys!!!! Am going to work on her tomorrow, just haven't had time yet. Me and carbs don't do so great. LOL
So if'n you hear tons of b****ing and screaming tomorrow....'tis just me. http://www.chevelles.com/forum/tongue.gif

Have printed up all your great thoughts and will keep it with me. My "Shevelle" bible so to speak!

Have a great one - oh, she did blow away a 351 Mustang tonight tho http://www.chevelles.com/forum/smile.gif Not bad for not running right!!

rachael anne