[cdunson]

I have a small problem with my 69 Camaro. I think its called "dieseling" where the engine runs for a second or two after the ignition is shut off. Then I get a puff of white smoke out of the carb. This is a 383 with XE274 CAM, HEI dist with 34 total advance, 14 at idle. TH350 with 2400 stall, 4.10 gears.

If I adjust the idle speed down a bit, the problem goes away. But I'd like the idle in Drive to be about 700. Because at 500 its pretty choppy. Sounds great, but a hassle worrying about keeping it running. Especially when the drag of the power steering or brakes kick in. When I adjust the idle up, I get the run on issue. Seems like any idle over 1000 in park causes the dieseling.

Looking for suggestions. So far I was told to open up the secondary idle a bit and close the primaries slightly. Or install an idle control solenoid. Any other ideas?

[JimM]

First thing I'd try is (if you haven't all ready) is put the vac advance hose on a full vacaum port.

Next I'd a peek at the plugs, maybe a colder plug would help.

Opening the secondary's won't help.

An idle solenoid will cure it if nothing else does.

[DjD]

You are on the right track, your pri throttle blade is open too far. You shouldn't need to open your sec throttle blade at all. the sec blade should be 100% closed but then turne the screw just a little so the blade isn't too far closed or it will bind.

As for your idle, you shouldn't need 1000 rpm in park to idle at 700 rpm in drive. If you do I bet you don't have a 2400 stall converter... Set your in park idle to 800 check and adjust your idle mixture screws for most vacuum or highest idle. Do all this with the vacuum advance disconnected and plugged just like you did with your timing. When done put the vacuum advance back but put it on a manifold source. This way you all the benefits of vacuum advance for part throttle and it adds timing to your initial idle timing. You may need to lower the idle some as teh added timing will raise it. This will make a big difference if the engine is pulling up against the torque converter which is really all I can think of for so much drop in rpm from park to in gear...

[freebird]

Hi There I had a similiar problem....it was so easy to fix in my case I totally overlooked it. I have a 670..turns out the return spring was weak...blades were not closeing after I decelerated..causing a high idle (around 1000 rpm and lots of run on) Put a front mount heavy return spring on and problem was solved.

Thanks

[cdunson]

Vacuum adv hose is on full manifold vacuum. Stall is confirmed at 2400rpm. It was just installed last week. Already checked the throttle return. It is returning ok. Plugs have a good coffee color to them, doesn't smell rich at all. Whats a good starting point for advance at idle with the vacuum can hooked up to full manifold vacuum? - I could adjust my can a bit.. if so, increase or decrease vacuum adv?

[JimM]

increasing advance at idle will raise your rpm (allowing you to close the throttles more)
You could run 16-20 degrees of vac advance.
What is you vacaum at idle in gear?
Is your advance fully deployed at that vacaum?

[DjD]

Jim's on it... I have to ask - how much is the idle dropping when placed in gear? I only see 100, maybe 150 rpm drop max in both my small blocks, one with a 700r4 and the other a TH350. In gear idle should be as low as you can without stalling once the temp guage starts climbing. It will be slightly higher once completely warmed up.

[baracda]

I would say Jim is on it too, sounds like timing is not right.

[zdld17]

Do look at those rear throttle plate stops anyway.. this problem is not just associated with Holley. You just need more tuning.

[cdunson]

Well.. I thought I'd report back. Checked the secondary throttle plate stop, adjusted it open a bit. Timing at idle set to 16, with vacuum adv its 34. Total timing of 36 all in by 3200. The vacuum adv required adjustment as I was only getting 25 degrees of advance at idle before. I now have the idle speed set to just about 1000 and it drops to about 750 in gear. Run-on issue appears to be gone. I beleive the fix was the timing and opening the secondaries a smidge.

I have another small block car with almost the same motor and it runs like a champ, so I setup the 69 as close to the same as I could get it. Sure helps having another car to reference.

[DjD]

I'm sure it's nice to be rid of the run-on but opening the sec throttle blades is just masking the real problem. There is no idle circuit on the secondary side of that carb so all you are doing by opening the sec throttle blade is adding air to the idle mixture.

[dnult]

Opening the secondary throttle plate stop is a trick to cure hesitation and back-fire as a result of having to open the primary throttle blades too far to get a decent idle speed. That condition is often caused by having a cam with low idle vacuum and / or too little idle speed timing. I think you have a different problem (than backfire and hesitation) so chances are the seconary throttle stop is fine where it is.