Quadrajet on auto 253 pre ignition

[shadow]

I recently rebuilt my carb to a workshop manual i found online.
She runs great BUT when i turn her off in park she keeps on running hissing and farting till it stops. If i turn her off in drive she stops fine. It's only idling about 950rpm in park when warm. I know it's not to lean.. any tips would be great........

[Goon]

Sounds like it needs a tune mate, look in ur manual for the idle and mixer screw.

Is 950rpm the correct idle rpm for park? a tune can also fix this

it can't be good for her being turned of in drive can it?

[253@7k]

Almost sounds like an ignition timing problem.

[vkberlina]

What fuel are you using?
Have you checked your timing?
What dizzy have you got?

[shadow]

timing 8 degrees
normal unleaded with additive
solid state

[vkberlina]

Unless the engine has been modified to run a low octane fuel the engine was built to run 96 octane fuel not 91, run it on 98 octane fuel and the pre-ignition will stop

[9C1pack]

Does it have one of those electric idle solenoid thingy's?
The type where when the ignition is on, an adjustable rod pokes out to move the linkage and set the idle, turn ignition off and it moves back and closes the carb, so it can't idle and/or run on.

[craigvk]

Does it have one of those electric idle solenoid thingy's?
The type where when the ignition is on, an adjustable rod pokes out to move the linkage and set the idle, turn ignition off and it moves back and closes the carb, so it can't idle and/or run on.

BINGO! A man of wisdom here. Take note fellas

Yes. As noted in the workshop manuals, the idle stop solenoid is basically a device that controls the throttle. When the ignition is switched off, the solenoid disengages and shouldn't produce any run-on.

From memory, the rpm of the motor at idle should be around 850 rpm and in drive around 650 rpm.

If you rebuilt the Quaddy 4 barrel, it should be fine. Other things to check in the future if missing might be pulling the sparkys out and giving them a clean. Other than the run-on, everything seems normal.

Just check the idle stop solenoid bolt which is adjustable. Maybe it's adjusted too far.

[shadow]

Thankyou for all the wonderful tips but the winner is.... 9C1Pack
I have adjusted and tested in the garage and it works. No more run on
It was about 5mm out. i would love to meet the guy who played with it last T25 screws cut to be flat bladed heads, worn screw heads and WAY to lean.. the spark plugs were the colour of my ass..
Thanks again and this is the first time I've toyed with a V8 so I'm sure I'll ask a few more. RB30's i know.. not V8