Low idle Problems

[Anonymous]

I'm having a problem maintaing a low idle. The carb is a single barrel Autolite/Holley on a stock 1966 170 with electronic dizzy. When I set the idle at the recomended 600 revs it stalls after letting off the accelerator from a high rev. I have been setting the idle up higher, but then it runs a little rough. I have not found vacuum leaks using WD40 around the carb, intake and vacuum lines. The vacuum reading off the intake manifold is a steady 18.5 inches at 600 rpm. The timing checks out fine. I can get it to idle at 600, only if I slowly bring it off of a high idle. Any ideas as to how to slow this horse down would be appreciated.

 

[Mercury Mike]

Is it an autolite, or a holley? If it's an autolite, and you have an automatic transmission version of it, make sure that you have the anti-stall dashpot correctly adjusted. It gives an extra shot of gas when you let off the pedal, allowing it to return to idle smoothly, rather than dying.

 

[fordconvert]

Does the idle mixtue screw respond or make any differnce? Where is the timing running at idle and is that with or without vac? Where are you getting the vac from? I assume DS2 dizzy? Single advance?

 

[pedal2themetal45]

Isn't 600 a little low anyway??? I think is should be between 650 and 700 shouldn't it guys??? and If its an automatic it would be 650 in drive not Nutrail. I'd say kick the idle up a little and if its running rough adjust the mixture and the timming at the new idle.

""""""65stang200 wrote:
anti-stall dashpot correctly adjusted. It gives an extra shot of gas when you let off the pedal"""""""

No it don't give it an extra shot of gas it stops the carb from returning to idle to fast and stalling the motor when ildes are low.

tim

 

[ludwig]

I think your idle is too low. When you put it in gear it pulls the engine revs down to a stall condition.

Warm idle for an automatic should be 700 and set in drive. Assuming that the timing is correct, get the idle rev right, then check your fuel/air mix with the vacuum guage. Run the mix screw in until it starts to starve out. Then back it out until the vacuum peaks. That should be a good mix. If it starts to get too hot, back it out a touch more. Running lean can cause a hot condition.

It is also possible that the timing is not as right as you think if the outside ring on your balancer has slipped. Use the vacuum guage to time for the highest vacuum. Then put the timing light on the mark and see if it is in spec. If not, you have to find TDC in the first cylinder, then put a tick on the balancer with a white pen or some other visible marker. You will have to time from this new mark that shows the true TDC.

 

[fb71]

Idle speed for an auto trans car is 750-850 rpm in Park/Neutral, and 600-700 rpm in Drive. Manual trans car should be 650-750 rpm in neutral.

 

[rommaster2]

wow, its good to know this info, i'll have to check my idle when i throw the engine back in and get it tottally right. I had it idling nice before we rebuilt the engine though so shouldnt be an issue. Man though when we were first starting, we got it to idle at probably about 50 to 100 rpms, the damn thing would just go BRRR...................................................................BRRR......................................

It was pretty great.

 

[Mercury Mike]

50 to 100 RPM?!

 

[Anonymous]

The 170 is in a bronco with a manual trans, so there is no dashpot. 600 is the specs for tuning and I plan to take it up about about 50 rpm's after I can get it running well The vacuum gauge is screwed into a brass fitting I put into place just below the carb on the intake. This the fitting where the vacuum wipers come off of.