High idle on my engine

[Joe Flanagan]

I've noticed that when I run my engine the idle seems high. I say "seems" because I have heard other flatheads run, notably Rodney B's, and mine isn't nearly that quiet. I have adjusted the idle mixture so that it runs smoothly. When I attempt to adjust the idle speed, all I can do is speed it up. The lowest setting (where I have it now) sounds too high to me. I have not actually checked RPMs, which I will attempt next chance I get.

Also, I have not yet adjusted the valves at operating temperature. They don't make any noise, but I'm going to check them at least and make sure they're according to specs. Would valve adjustment have anything to do with idle speed? My first thought is that it would not.

[jd52cranbrook]

Check for a vacume leak.

[Joe Flanagan]

Well, the first suspect would be the port where the line to the windshield wiper line goes into the intake manifold. I have a bolt in there now with teflon tape but maybe it's leaking. Can you check this sort of thing as in modern vehicles, by shooting some carb spray at the suspect area?

[aero3113]

Well, the first suspect would be the port where the line to the windshield wiper line goes into the intake manifold. I have a bolt in there now with teflon tape but maybe it's leaking. Can you check this sort of thing as in modern vehicles, by shooting some carb spray at the suspect area?

you can prob use the carb spray,people also use propane from a torch (don't lite it just use the gas)

[aero3113]

Check the carb mounting bolts also

[greg g]

UNLIT PROPANE TORCH. Hook a Vacuum gauge to your wiper port and see how it reads.

Take a look at the actual screw for the idle adj. See if there is an aig gap between the screw and the stop when you say you can't adjust lower. If this is the case you main linkage may need to be adjusted as it may not be allowint the throttle butterfly to close all the way. If the trottle butterfly is not fully closed (look down the carb with a good light to verify) The idle circuit is not engaged so it won't respond to adjustments to the slower side. rpm should be in the 450 to 550 rpm range on a healthy engine.

My guess the noise issue compared to Rodneys is likely mostly from the fan.

[Joe Flanagan]

Thank you, everyone, for your answers. That gives me plenty of work to do. I will get on it as soon as it stops raining here. Probably another two days or so. I think Greg might have hit on something because the way the idle speed screw sits in relation to the stop just doesn't look right to me. I might have the linkage buggered up a little. Haven't really taken the time to investigate.

[Tom Skinner]

Joe,

If your Idle Mixture Screw is not conicle at the tip-that is to say maybe it has been screwed in to far and damaged, then you will never achieve a smooth/slow idle. if it is damaged repair or replace it.

It could be something as simple as that without using propane etc.

I have found that looking for the simplest solutions first save time and money.

If I knew how to attach pictures here I would attach a picture of a normal Idle Screw but I never can figure out how.

I got lucky once and attached a picture of my car and me to my name in the directory.

Tom Skinner

Huntersville, NC

[Joe Flanagan]

Thanks very much, Tom. I will take a look at the end of the screw. So it should kind of taper to a point at the end?

[Tom Skinner]

Yes-but not a sharp point

[mackster]

when my engine was running, it sounded like it was bearly on until you stepped on the gas. . .I heard another near by and it was very much alike. Wonder how yours sounds?????

[Jim Yergin]

Joe,

I will be interested in what you find. I have the same problem with mine. The idle adjustment screw is back all the way and not even touching. I tried but could not find a vacuum leak with the propane technique.

Jim Yergin

[Joe Flanagan]

Sounds like it's racing a little. The front clip is off, so that might be part of it.

[Joe Flanagan]

The throttle cable is not attached at the moment.

Jim, I'll keep this thread updated so you can check in.

[DutchEdwin]

Joe,

When I first started up my engine I didn't check my carb settings.

The engine ran very bad. My case was float needles not shutting off making a hard idling engine. After I cleaned the carb with thinner (all the chambers and passages). cleaned it about 3 times with letting the thinner do it's work for 10 minutes to dissolve the gunk and blow all the passages with an airgun at 6 bars. Installed the overhaul kit, adjusted all the settings that had to be done according to the manual. Man they were way off. Also took the time to get the play out of the rod connections by adding little washers to the joints. Now the engine is idling smooth, and can be adjusted easy. When you do a thing like this, get a timing light, tachometer to read the engine rpm and a vacuum meter to read the engines vacuum. This will make things a lot easier to diagnose and less frustrating, although I'm still not fully satisfied about my settings but the engine sounds good and runs good and I do not want to steal your thread so I do not talk about that here. good luck.

[Joe Flanagan]

Thanks Edwin. Don't worry about stealing my thread. All that information is useful. I rebuilt my carburetor and cleaned it out very thoroughly. The float is set per factory specs. Needle is new. I haven't had the time lately to really dive into this. Good point about the vacuum gauge, tachometer, and timing light. I'll make sure I have those on hand. Frustration is something I don't want. Here's a question: I have a tach/dwell meter but can I use it on a six volt system? I thought I read a thread here where someone (Shel?) had trouble getting one to work.

[Flatie46]

A friend of mine just got an old mustang going that had been sitting for years. He pulled the tank had it cleaned and sealed. He replaced all the lines from tank to carb and rebuilt the carb. Now you wouldn't believe the trash he's cleaned outta the carb[ 3 times ]. I know some of it was in the fuel pump but it's amazing what kinda trash you'll get in you carb even when you've gone through the system. Just something to think about.

[Joe Flanagan]

Thanks, Flattie. I will check that out as well. It wouldn't surprise me if I have stuff coming up from the tank even though I had it dipped and stripped.

[P-12 Tommy]

Thanks Edwin. Don't worry about stealing my thread. All that information is useful. I rebuilt my carburetor and cleaned it out very thoroughly. The float is set per factory specs. Needle is new. I haven't had the time lately to really dive into this. Good point about the vacuum gauge, tachometer, and timing light. I'll make sure I have those on hand. Frustration is something I don't want. Here's a question: I have a tach/dwell meter but can I use it on a six volt system? I thought I read a thread here where someone (Shel?) had trouble getting one to work.

Hey Joe, I hook the power of my tach to another car(12 volt) and it works fine.

Tom

[Merle Coggins]

I have a tach/dwell meter but can I use it on a six volt system?

How many wires on your tach/dwell meter? Mine has 2 and is marketed for 12v systems. The directions say to connect the red one to the wire between the coil and distributor and connect the black one to ground. Since most 12v points systems use a ballast resistor to reduce the voltage at the coil, I figured it should work on my 6v system. I connected the wires reverse of the instructions, since the current flow of a pos ground system is reverse of a neg ground system, and it works great.

If yours has power wires besides the signal wires then you'll need to connect it to the right voltage power source. But if it's self powered it'll work on 6v.

Merle

[DutchEdwin]

I have a tach/dwell meter but can I use it on a six volt system? I thought I read a thread here where someone (Shel?) had trouble getting one to work.

Jo, I used the 6V battery from my car. No problem, even out of the garage I could see the mark clearly. In case you cannot, someone suggested in an earlier post to use the wire that runs between the coil and distributor cap. You get more light as the strobe flashes on all 6 sparks but read the timing only on the #1. I tried that and it works but I had enough light on the #1.

[Joe Flanagan]

Thanks, Edwin. I started my engine today and discovered why the idle is high:

The throttle sticks. I pushed it down with my finger and the car idles beautifully. Rev the throttle and it sticks back up on high idle again. Push the throttle down with my finger and the idle is nice. It's just sticking. So I guess I'll need to do some cleaning and de-gunking.

[greg g]

Check the high idle cam ( a piece of sheet metal wrapped around the trottle shaft to provide a ramp for the idle screw to ride on. Its kinda redundant if you have a working hand throttle so it can be removed. 60 + years of wear may allow it to hang up and interfere with the screw reagdless of the linkage being correct.

[Joe Flanagan]

There is such a creature on the carburetor. I've called it quits for the evening. Have to diagnose a problem with my daily driver now.

[P-12 Tommy]

Joe, Also check your floorboard grommet where your gas pedal linkage goes through. My throttle used to hang up a little and discovered mine was missing. And check the linkage return spring on your engine.

Tom