1969 Cutlass 350/310. Auto. Set dwell to 30, it was slightly off. Idle was low, about 650, raised to a 825 or so while in park. Checked timing, set to 8.
Car is now running on for a few seconds after shut off. Started doing this after setting dwell and idle, had hoped setting timing would help, no luck.
Burning 90oct ethanol free, runs good, and shut off fine previously.
Do I need higher octane? Car is stock, prefer ethanol free but 90 is highest close by.
From what I’ve read online high idle can cause this, should I drop it some? Did double check idle and dwell with different meter.
First time tuning a car, amazed how easy things were to adjust.
Any ideas appreciated.

 

Higher octane would be better. You could continue with non-ethanol and add octane booster. Yes try reducing the idle in 50 rpm increments. Next try bringing the timing back to 6° BTDC.

This can also be caused by excess heat, are the temps ok? Carbon buildup retains heat and can also cause this. Obviously several possibilities so try the solutions one at a time to know what works.

Good luck!!!

 

Thanks, it’s running cool, was about 180 when driving today. Did replace plugs. Will try adjusting idle.

 

Lower your 825 or so idle speed back to 650.

 

Learned something, I was checking idle after only having the car idle in the driveway about 5-10 minutes. Checked again after a longer drive, idle was actually 900, must increase as motor gets warmer. Set idle to 800, she shut right off.
Thanks for the advice.

 

Gotta love the simple fixes. There is really no reason to idle it that high if your running a stock engine.

 

You need to perform the full routine as described in the CSM (or the tag on your radiator shroud). You can't stop in the middle.

Assuming you have a good set of contact points:

(1) Establish dwell at 30°,
(2) Set timing (ensure you disconnect/plug vacuum hose) to specification on TUNE-UP LABEL (my 350 is set to 12° BTDC)
(3) Adjust your A/F mixture (correctly).

Be sure you have a working carburetor dash pot when you're establishing your slow idle. A failed or maladjusted dash pot can result in issues if (in particular) the dash pot has limited freedom of movement &/or not adjusted correctly.

 

I guess you got it. I took my time responding and missed the posts.

 

Agreed. The factory idle RPM is not that high.

 

not according to the csm

 

That looks to be the instructions for setting the timing?

Is there another section that shows the curb idle speed adjustment? If I recall correctly, my 1970 Supreme 350 (same engine as yours) curb idlw was specified as 625 in Drive.

 

Both fast idle and slow idle adjustments/specifications are contained in the Carburetor Adjustments section of the CSM. I'm familiar with neither the specifications nor the availability of carburetors for the 1969 350 cid; yet, both the slow idle RPM & fast idle RPM differs among the various carburetors (MV, 2GC, 4MC) employed on the 350 engine. Section 6M of the 1971 CSM.

 

Mine should be 575 in drive according to the CSM.
I’ll check that next. Thx

 

Sounds about right. I have the 350 cid, 4bbl Q-Jet, AT w/ AC. My low idle is set to ~750 RPM (as I recall) w/ the AC in the OFF position. If AC is ON, the engine and RPM remain stable ~650 RPM. I've owned my '71 CS three years. A car w/ AC is generally always going to have a higher slow idle than a car w/o AC. I have no idea if it's the original cam - it does have a little mild lope to it, but I have no idea if the cam has been changed.