Holley 4150 HELP

[Xterminator]

Hi! I sure hope someopne out there can help me out. I recently bought a 69 GTX. Its got a Holley model 4150 on it. When I first got it, it ran but wouldn't idle below 1500 rpm. The guy I bought it from was a broker and didn't have any history on the car. I was able to track down the previous owner but he wasn't very helpful. Seems he bought the car 9 years ago and it mostly sat in his garage. He also had a Roadrunner and decided to concentrate on that, so he sold the GTX. The broker retarded the timing so it would idle below 1500 rpm. When I started to work on it , I found that the fuel system, including the carb, was full of rust. I got a new tank and sender, cleaned out the fuel lines with carb cleaner and compressed air till it ran clear, and rebuilt the carb. The carb bowls had about a half inch of rusty sludge in them. I was surprised that it even ran. After cleaning and rebuilding the carb, It still will not idle below 1500 rpm. The carb sits on an adaptor plate (i guess) that's about a half inch high. All the extra vacuum lines have been plugged and the mechanical choke has been replaced with an electric one. At idle(after warm up) the choke is wide open and both primary and secondary throttle plates are in the closed position. I even disconnected the throttle linkage and set the idle screw completely counter-clockwise. Still idles at about 1500 rpm. HELP HELP HELP! Bill E.

[dwc43]

Sounds like a vacuum leak. It it's stock it should not need that plate. I'd ditch it. Never known a stock one to have a plate.

[motorhead]

Once you have made sure that you do not have a vacumn leak check to be sure that the secondary throtle plates are not adjusted open too far,this adjustment is on the passenger side of carburator and if incorrectly set up will cause engine to race and backing off the primary screw will not change it (in most cases the carb needs to be removed to make this adjustment as the screw is upside down and you can not access it while bolted to intake)this is something to consider after what you have already done to find your problem
hope I was of some help
Good luck

[Boozoo]

Just so we're all on the same page here.....

When you say it won't idle below 1500.... is that because it won't adjust any lower or because it dies when you try to go lower?

PS... one of the "dumbass" things that bit me once was the throttle cable was adjusted far enough back on one car I looked at that it became the limiting factor after the idle screw was backed out. All my cars prior to that had been 50's vintage with mechanical linkage hehehe


PPS Have you reset the timing to something you're comfortable with yet? You can set it for total advance for now and check the initial advance when you get the idle sorted out.

[Xterminator]

I think I'm gettin close. I took off the carb and backed the secondary limit screw out and that brought the idle down quite a bit. Before it just would not go any lower, it wouldn'd die, just no adjustment. I even took the throttle linkage off just to be sure that it was not the problem. Still idles a little high but I' going to check all the vacuum lines and gaskets again for leaks. Maybe I'll find it there. I might even back off the secondary limit screw another quarter of a turn. The advise I got on that was to turn it until it just touched the stop and then go another quarter of a turn. You were right on. A small ajjustment on that screw sure makes a big difference. Another thing I found was that the last owner or the one before, hooked the throttle linkage to the wrong spot on the Holley. Full throttle on the pedal only opened the butterflies about 3/4 of the way. I drilled out the linkage lever on the carb and repositioned the throttle cable. Now the butterflies are closed with the pedal fully up and I can get full throttle when it's to the floor. Maybe that was a good thing because he never got to run it at full throttle. Guess 3/4 was good enough for him. Thanks for all the info. Bill E.

[Joe Brown]

Which intake manifold are you using. If your using a M-l Mopar then check the carb stud holes. Mopar drilled some of these all the way thru, which gives you a big vacumn leak. The 4150 doesn't cover the unused carb stud holes. You can tell easily by starting the car and put your finger over the carb stud holes. Hope this helps.

[Xterminator]

I think it's the stock intake that originally had a Carter AVS on it. There's an adaptor plate between the manifold and the Holley which seems to take care of the difference. I' did get the idle to settle down by adjusting the secondary butterfly stop. It was backed out to far. Bill E.