69 Torino Cobra 428CJ - Ford Muscle Forums : Ford Muscle Cars Tech Forum

dmac · 02-16-2013, 05:17 PM

A friend brought me this car to get it running right. It is an original car. The engine was overhauled by a reputable shop and the car has not been driven much since then. I originally thought the carburetor (4150 Holley) needed overhaul and put a kit in it. It is clean and all the settings are correct per holley instructions. The car has a comp cams aftermarket cam in it but per comp cams website it is correct for the application and should have a lumpy idle. The engine will not idle correctly. It oscillates RPM and seems to miss at idle. Runs good on the highway. The plugs are new. Wires are new. Firing order is verified correct. Timing has been checked. Compression checks good on all cylinders. Carb overhaul seems to have had no effect. The pcv seems to pull a lot of air through the engine. Would a defective pcv cause a problem like this. I am not very familiar with Ford vehicles. The cam can be heard at idle but the engine shakes and acts like it is missing in addition to the lumpy idle. The point gap is correct also. Engine seems to like around 18 to 20 degrees BTC with vacuum advance disconnected and plugged. Any help appreciated from some of you Ford Experts.
Thanks,
dmac

bartlettracing · 02-16-2013, 05:41 PM

I would test vaccume , and disconnect and plug all vaccume lines first. if you find nothing wrong there I would pull spark plugs and see what they look like. make sure there all firing. then if nothing to bad I would pull valve covers and see if every thing looks good there. make sure it didnt wipe the cam,broken rocker,bent push rod ect ect .....

My427stang · 02-17-2013, 06:10 AM

Questions

1 - Where are the two idle a/f mixture screws set? They should end up around 1 1/8 turns out at best idle and set the same. Ending up somewhere else or not having an effect is an indicator of a vacuum leak.

2 - Is the ported vacuum that feeds the distributor alive at idle? It should be dead at idle. If it has vacuum, the primary plates are too far open, which could be because the secondary idle is closed too much, or it could be that it has a vacuum leak and the idle has to be opened too far to compensate

3 - Have you tried letting it idle with the vac advance unhooked? Some Ford distributors end up with a worn pigtail to the points, at some locations of the distributor pla6te, the wire can break contact or short out. Not common. In addition, if this helps and the vacuum is alive at idle, it may just be tuning or again it could be a vacuum leak

4 - Finally, see if he can find out if they used Felpro Printoseal intake gaskets. They do not work well on an FE

It of course could be a wiped cam, hopefully not

dmac · 02-17-2013, 11:21 AM

Thanks for the tips. I think there is some ported vacuum at idle. I will check the throttle plates. The plugs look ok and are new. I have adjusted the idle mixtures with a vacuum gage to get the most vacuum. I think they did best around two turns out. Will re-check that. I have run the engine with no vacuum advance and it makes no appreciable difference. I really have felt it was a vacuum or carburetion issue but can't put my finger on it. I'll go through your list of possibilities. Thanks again.

dmac · 02-20-2013, 06:04 PM

The problem is the carburetor. Put a known good 650 Dbl Pumper on it and it runs great. Thanks for the tips.

My427stang · 02-21-2013, 04:37 AM

The problem may have been fixed with another carb, but if you had ported vacuum alive, you were into the transition circuit which affects idle AND makes the transition circuit not work properly when it should be working

This also can drive the incorrect a/f mixtures, which when correct, should be somewhere around 1 1/8 turns out on a 2 corner idle like the D0ZF-AB

Not saying the carb is good, it may indeed need work, but it was not correctly set up if the ported vacuum was alive at all at idle.