idle RPM's on stock 260

[chillzatl]

What should a stock 260 be idling at? I'm at around 800rpm cold and 1200 RPM once it warms up, in park. Thanks!

Oh, another question. I saw on the 260 spec sheet that the F code should have a .016 plug gap and the D code a .035 gap. Anyone know why they have such a big difference when spec wise, they're so similar?

[Comechero65]

260 /289 same specs - .032"- .036" plug gap. The .016" is most likely the point gap.

If it's idling that high after warm up, either the choke is not opening all the way or the high idle mechanism is not resetting all the way. Break out the carb cleaner.
Ron

[Groover]

Can not imagine the .016 spark gap? Book says .032 - .036 number. Book says about 500 RPM curb idle (warmed up, in drive with your foot on the brake) -- for an automatic.

I'm assuming your 1200 rpm is in Park. That seems a little high to me.

For my stock rebuilt 260 it runs about 800 RPM in Park or Neutral to get about 525 in drive with foot on the brake. In the summer I can set it lower, but in winter if I lower it, it sometimes stalls out in drive.

For a manual, you can run it a little lower I'd say.

Here's book on the plugs:
http://falconfaq.dyndns.org/display1.ph ... Page=9-031

Here's book on the RPM:
http://falconfaq.dyndns.org/display1.ph ... Page=8-073

Believe there was a Service Bulletin that later said set 25-50 RPM higher than the book value to avoid some stalling issues.

So curb idle of 525-575 seems about right.

What happens if you lower yours?

[chillzatl]

Derp, yes, that was points gap... -1 for not paying attention...

So it's 11-1200 in park, 600ish in gear. If I lower it to around 800 in park, it drops to 450ish in gear and runs rough, lots of vibration. The motor isn't jumping/shaking but it feels rough through the steering wheel, like it's struggling to not die out. Revs great though, but once it goes back to idle it's super rough.

[Groover]

Well I guess practical says the lowest you can get for curb idle and have it run smooth. So if that's it, then that's it, but the spread does seem a bit high. Maybe like noted above, your choke is not opening all the way? or you have some sort of fuel leak bypassing the idle circuit? Bad power valve?

[comethead]

600 rpm drop when shifting into drive? Doesn't sound right.
Seems like rechecking idle mixture and speed would help.
Also, could there be a torque converter issue affecting engine idle speed when in drive?
What changes from park to drive? Something is pulling the engine speed waaay down.
Good luck!

Joe

[chillzatl]

Thanks for the replies. Is there any sort of base setting for the choke that would be considered stock? I tried opening it up some and it kicked the car out of high idle, but as mentioned, it was really rough idle in gear. I tried going the other way, closed the choke off some, which kicked it into high idle, then adjusted the idle screw down. This got me at around 900 RPM park idle and 500ish in gear and everything was smooth. The weird thing now though is that the cut out that I mentioned previously in another post is back. Also the rumble of the motor just doesn't feel right. There's a surge to it. Instead of a steady brbrbrbrbrbrbr rumble I'm getting a brbrbrBRbrbrbrBRBRbrbrbrbrBRbrbrBR. Hope that makes sense. In both cases, regardless of how I set things, the car pulls pretty hard through the gears.

Just to give a little more background. The car was pretty much all original. I've replaced the carburetor, fuel pump, plugs, wires, distributor cap and vacuum advance valve. Thanks again for the help and suggestions so far!

[gmsnowball]

Check your timing and your idle air adjustment. Use POP's tried and true method, a 1/2 inch wrench and a screw driver is all you need to tune a SBF. Oh, you also need a good ear.
I had idle problems with my new motor until I sicked the 1/2 wrench after it.

[chillzatl]

Check your timing and your idle air adjustment. Use POP's tried and true method, a 1/2 inch wrench and a screw driver is all you need to tune a SBF. Oh, you also need a good ear.
I had idle problems with my new motor until I sicked the 1/2 wrench after it.

I set the timing this past weekend. It was slightly advanced, but not too bad out. Which screw is the idle air adjustment? THanks!

[Groover]

Check your timing and your idle air adjustment. Use POP's tried and true method, a 1/2 inch wrench and a screw driver is all you need to tune a SBF. Oh, you also need a good ear.
I had idle problems with my new motor until I sicked the 1/2 wrench after it.

I set the timing this past weekend. It was slightly advanced, but not too bad out. Which screw is the idle air adjustment? THanks!

Screw(s)... two on the front of the carb. Pointing out at slight angles off of perpendicular to the carb.

Here's the whole setup for an autolite 2100:
http://falconfaq.dyndns.org/display1.ph ... age=10-024

[Tbart]

Maybe vacuum leaks. Base of carb, intake, hoses. Set idle mixture by adjusting screws at front base for fastest idle. Then turn it down with the throttle stop screw. That's how I do it anyway.