Curb idle speed

[Stang_1973]

So Ive now checked into one of the reasons i have engine run on. I think my throttle plates were open too far so i decided to check curb idle speed. And i found that i was at about 1000 rpm when in D. According to justmustangs.com specs page a stock 73 302 should be at 575, so im guessing my throttle blades were open too far. However my car is not stock at all comnpared to a 73 302.

according to the mods in my sig, should my curb idle speed remain at 575 or should it be higher or lower?

 

[woodsnake]

Each engine responds differently to everything. A carbureted is not an exact science.

My hot rodded 289 idles at around 750. You will just have to find what works best for your engine.

I will agree that 1000 seems a bit high, but not unreasonably so.

A vacuum guage and a timing light are your best tools on these old POS Fords.

(Oh wait, I was just reading that 5.3L thread.......I LOVE old Fords!)

 

[brianj5600]

I you have run on it is not the carb. Anytime the engine is turning, it is pulling air and fuel in through a carb. Carbrated engines turn off by removing spark. My guess is that your ignition system is getting power from something. Does pertronics have a tech line?

As far as idle, it should not take 1000 rpm to idle with that cam. The later intake valve closing will cause it to need more initial timing. I would use 14 degrees minimum initial timing. Even 20 degrees might be needed to get it to idle best. It may require limiting mechanical advance depending on what distributer you have.

 

[Stang_1973]

I thought it was timing a while a go but a fellow stangnetter said timing shouldnt be the problem....

anyway, i got my idle down to 600 without it dieing and it seems to be doing pretty good. You can tell it has a mild cam more now. before it sounded like way too accelerated.

Ive been meaning to get a vacuum gauge so i can better tune the carb, and prolly a timing light to see where that is.

But so far i havent had engine run on since bringing it down.

any other experiences with mild setups like these or suggestions are definately appreciated.

 

[Stang_1973]

actually what the fellow stangnetter said was that it could be that fuel was getting into the engine if the the throttle plates were far too open at idle allow the fuel to diesel out, or ignite in hotspots, causing the run on.

And sisnce closing the throttle blades or bringing down the curb idle speed, has apparently stopped the run on, i guess that was it. but i simply want to know what the best idle speed would be with my setup.

 

[brianj5600]

600 is plenty low. I don't think there is a specific number. At 1000 it probably slammed into gear from neutral. Much above 700 gets a little uncomfortable when putting it in gear unless the converter is loose.

 

[Stang_1973]

yup it would lurch into gear everytime. Had to be standing on the brake and when at stop lights id have to press down pretty hard to keep the car from moving. The car would go through all three gears without using the accelerator!