I will do that I did put a new vauum wiper motor on the car like three or four weeks ago maybe one of the old original hoses finally broke somewhere. I didn't mess with the car today but I do plan on pulling the carb off just to check the passages on the fuel circuits as well as to clean out the carb since it has been getting fine rust particles in it. I feel more comfortable doing this so I can rule out the carb for sure as I start looking for a vacuum leak.

 

It sure won't hurt to go through the carb. It will be interesting to see how much crap the filter didn't stop..

 

Went through the carb on Thursday at work. Was slow and boss wasn't around after lunch so I took a break and tore into the carb. Honestly what I saw still had me concerned as it was not that dirty inside. There was very fine rust particles throughout the carb but I blew everything out including the filter with carb cleaner and compressed air.


Threw it back on the car after work with the idle mixtures set to 3 turns from seat and once the bowl got filled up started up and ran smooth. Had to turn the idle speed screw down half a turn to take it back to its 800-850 rpm idle that it had before.


I don't think it was anything to do with the carb internally but I did notice the four nuts that held the carb down did seem a little loose. So its hard to say if the cleaning did the fix or reinstalling the carb and tightening down the carb after installation.


All I need to do is replug in the vacuum wiper hose to the power brake port on the back of the carb.

 

What does the manual say? Usually 1 and 1/2 turns out from seated. Whatever that figure is in the manual, use it. It's only a ballpark figure to get started, literally. But it will need leaning out, not enriching, for final adjustment. The reason being, as I mentioned earlier it is possible to get the engine to run, but it won't run right. Here's why - we want the idle circuit to be the only source of fuel at idle. So set the idle mixture to starting spec, then adjust RPM screw to get it to start and run, in that order. It may run like %h!t, but that's OK.

THEN turn the idle mixture screws IN equally, the Idle RPM will increase, readjust RPM screw down to spec. Continue back and forth until idle smoooths out until no improvement can be had - maximum vacuum or RPM increase. With my truck, the sweet spot ends up with both idle mixture screws 1/2 turn out from fully seated for example.The idea is to make the carb work, we want maximum velocity and atomization of the fuel by leaning out the fuel/air mixture as much as practical. Another way to tell, the butterflies should be almost completely closed at idle. This is important.

 

The valves are almost closed all the way as it is now. I tried turning down to 2 turns out but engine wants to run rough. I could compensate by bringing the idle speed up on the screw but that will then open the valves enough to start bringing in fuel from the primary circuit.


Not sure if a 2bbl will be able to run on 1/2 turn but I can give it a try I believe right now I got it set at 3 1/2 turns on passenger side and 3 turns on driver side.


As far as the manual goes, that is out the window as this is a early to mid '70s Motorcraft 2100 2bbl carb. The manual would only cover the Holley 4000 which will help me greatly when I get around to rebuilding it so I can put it back on the car.

 

Well every engine is going to be different, and also carburetors, production tolerances, etc. BUT, there is a stock setup starting point for that engine. Typically that will be plenty rich, and the needles are turned in for "lean drop". 3 turns out would have most idle mixture screws falling out? That just doesn't sound right. Hm.

 

I know it sounds excessive but I have unscrewed it 6 turns and they didn't fall out when I was messing with it before I took the carb apart to clean it again.


I do still want to try and get the rpm more rock steady and remove the vibration in the car itself which is more when its in gear. So I will keep that in mind and play with the settings some. Might try turning the idle mixture screws in and idling the speed up to see what that does.

 

The 800-850rpm idle speed sounds high. Do you have a manual for it? The correct idle speed will apply no matter the carb used.

You can tune the idle circuit with a vacuum gauge. Adjust the idle stop screw for the correct idle speed. Fit a vacuum gauge, and adjust the mixture screws in or out, until you have the highest vacuum reading. The idle speed will change while you do this. Re adjust the idle stop screw for the correct idle speed and repeat the mixture screw adjustment, again watching for the highest vacuum. Repeat until you've found the ideal setting.

As a test of the idle circuit, with the engine idling, you can screw one of the mixture screws all the way in. If things are good, the engine will die. If it keeps running, then you are getting fuel from someplace other than the idle circuit - a blown power valve or the equivalent, the throttle opened too far and activating the boosters, etc.

 

Once I can locate my vacuum gauge I will try to do some more tuning on it. I have it set at 800 as in gear it is 600 rpm at idle. The shop manual spec is to set it initially at 475-500 in neutral then make final adjustment in drive to 425 to 450 rpm.


I honestly don't believe I can idle this engine down that far and I am confident that if I did the generator light would come on just idling. But I will give it a try and see if I cant idle it down to spec.

 

It should idle 475-500 in neutral with no problem, if it won't you have a problem somewhere. Be sure to recheck the timing at that RPM, running at the higher RPM might have the advance unit advancing and giving a false reading if it wasn't disconnected.

 

Oh I can idle it down to 600 easily in neutral probably even 400. Just know that anything under 600 rpm and the generator light starts to flicker on.


Well I finally found my vacuum gauge will probably work on the car tomorrow during lunch.


I ran the car some and its not quite perfect on running weather is cooling up some so that might be part of it as the engine hasn't been running in cold weather so will be a first for me. But hope to get the engine running back smooth and if I can get it to idle down around 450 in gear I will.

 

The generator light coming on is a separate problem and turning the idle up isn't a good way to correct it...

 

It's not so much of a problem as a quirk of generators. They just don't produce current at idle, so the regulator cutout disconnects to prevent backfeed. One reason alternators replaced them. It's true, the maintenance adjustments for carburetor tuning and such need to be done at idle spec.

 

Thats not entirely true, Yes an alternator will charge better at low RPM but millions of cars ran with generators and low idle speeds without the light coming on. I've owned dozens from the 50-60's era over the years without a problem. Still have a generator on my 60 truck and it idles at 475 without the light coming on.

 

well I took and set my idle speed screw to half turn from fully closed I then used vacuum gauge and my tach/dwell meter to set the carb. Down side, I cant get the idle speed below 750 if I close the throttle plates all the way. Half turn out is 800 rpm. I do how ever have a very steady idle now and almost 19" of vacuum at idle that is steady.


I believe the only way I could get the idle speed to go down is to adjust the timing which I really don't want to do as the car starts too good and runs too good to go screwing with it.


In gear I am running right at 625 rpm in gear and no generator light.






I also turned one idle mixture screw in all the way, engine ran very rough and quickly stalled out. So the carb is set ideal based off what I have heard to date.