66 289 high idle issues

[Bret Weymouth]

I am helping a friend on a 66 Mustang. I do not know what the specs are on the motor. The previous owner bought it from a Ford Dealer Mechanic. It sounds pretty good so I would have to say it is not a stock cam. It has a Edelbrock performer manifold and a Holley 600. Trans is a C4. We went to put a Electronic distributor in it. I would get it all timed @ 08 deg adv then hook the vacuum advance line up and nail the gas and the idel would take off and the timing would be way advanced and take a couple minuites to come down. The distributor was one of the e-bay Procomp's. I called procomp and they said there was an adjustment inside of the cannister and take an allen key. They could not tell me what size allen key and I could not get it to adjust. My friend went and bought a stock rebuilt distributor. I installed and the same thing. With the vacuum advance line off of it and plugged I have it timed @ 8 deg adv. I nail the carb and only get a couple deg advancement and runs great. I plug the vacuum line in and do the same thing and the iddle goes way up and the timing goes off the chart. My 8 deg timing mark is setting at almost 12 oclock on the motor when doing this. I unplug the vacuum and the timing goes back and the idle is fine. Is there a vacuum reducer that should go in line to reduce the vacuum to the advance cannister? Any help with this would be appriciated.

Thanks,

Bret

 

[woodsnake]

I think you have leak some where, or a split hose.....

 

[2+2GT]

If you are getting vacuum advance at all during idle, the advance is connected wrong. It should be on the ported vacuum port on the carb. The 66 289 should be connected like this diagram. The advance port on the Holley in on the right side of the front bowl metering plate. BTW, the advance curve of both the vacuum and centrifugal advance almost certainly needs to be set. Even fresh reman distributors are usually way off, and need to be adjusted. The best way by far is to pull the distributor and have it done in a distributor machine.

 

[Bret Weymouth]

Thank you for the information. I do have it in the metering block and it is not advancing off of a idle. It is once you nail the throttle the vacuum kicks in the advance goes too far and takes a long time to come back to the correct iddle. It is almost like it gets stuck. This has happened with both the Porcomp and the stock rebuilt distributors that I have tried. I will look for someone with a distributor machine and get it dialed in.

Thanks,

Bret

 

[woodsnake]

Do you have the vacuum advance with with the adjusting screw in it? There's like a 3/32 hex head or something in there you can adjust it with....

 

[S-Car-Go]

This sounds way wrong. With vac adv, disconnected it idles at 8* BTDC, and then advances a "couple of degrees" when you rev it? That's a problem. You are going to want something like ~30-36* total by 3,000 rpms, not a couple of degrees. Every car is a little different. That's for the the mechanical advance.

Vacuum advance should not be effected at idle, plugged into the metering block. Hook up a vac gauge and see what you are getting at the carb and if it takes a long time to bleed down after you rev it. Maybe you have a cracked metering block? Something goofy with the carb if this is happening with more than one distributor.
BTW, it doesn't hurt to drive w/o vac advance. It's for milage. Tune the car with the mechanical advance first, then tweek the vac advance with the 3/32 allen. Or as 2+2 suggested, have it done on a machine.

 

[Bret Weymouth]

thank you i will give it a try and see what happens.

 

[woodsnake]

Also, if you have a vacuum gauge, you can check and see what kind of vacuum you are getting. That will show you if you have a leak, or help determine if you have a cam in it.

The two things that a guy must have if you are going to work on an old car is a vacuum gauge and a timing light! You just can't get away from that......

 

[onlymustangford]

I agree with woodsnake. I was going to suggest that you tee in a vacuum gauge and pull readings from idle, off idle etc and see what you get.

And check it out with a vacuum gauge.

You will also see if what 2+2 said is right. If you show any vacuum at idle you either don't have the hose in a ported vacuum outlet, or something is wrong with that port.

Good time to find out if you have a cracked hose as well.