carter carb function

[Vgrizzw]

Need help from the den on some basic carter carb operations.  Ill preface that i lost my clutch pedal the other day and went in to replace the master, slave, hose and add a reservoir.  In the process of tear-down I came to my questions.

I removed the carb filter and housing just to notice that the butterfly was wide open and floppy like it wasn't connected....  The passenger side was in fact not hooked up to what i believe to be the choke housing (which would explain my cold start troubles) but the butterfly still didn't close on its own??  Before I dig too deep I want to make sure it isn't vacuum controlled? I also noticed a trim screw missing; one that would hit a "stepped" plastic piece that's on the butterfly linkage.

That being said the car has run good to me since i bought it a couple of months ago besides taking a few turns when she is cold and I'm also getting relatively good mpg so I haven't even thought the carb to be defective other than my choke.

[carnuck]

The choke butterfly only closes all the way when the throttle is opened because the high idle screw is on a step on the side.

[macdude443]

^ Right.  When you start the car cold, you push the pedal once to set the choke.  This allows the choke's bi-metallic spring to snap the butterfly shut (it hangs up on the fast idle cam, the stepped part, as the engine and choke cool).  Once the cold motor turns over and catches, engine vacuum will cause the vacuum actuator at the back of the carb to force the butterfly open to a specified clearance.  This is so the engine gets enough airflow to remain running (if not adjusted to spec this can cause an immediate stall).  As the engine warms, the choke coil opens the butterfly slowly.  The butterfly is linked to the fast idle cam and as it opens, the cam steps will step down until idle speed is reached (you must blip the throttle as it warms up to step it down).  There are two screws.  One for fast idle and one for curb idle.  The two in the front are the idle mixture screws and should not be used to set idle speed.

[Vgrizzw]

Ok, I figured it might be vacuum operated. I'm missing the trim screw for the fast idle cam and the choke wasn't hooked up, but like I said the car runs good. While we're on the subject (and considering my car runs "good") is it worth while to do the 2150 swap? Could my car run even better than it does now? Mpg get even better?

[mo.eagles]

With the Carter on Thing 2 I was getting about 8 mpg and it idled like crap . Put on a 2100 and doubled my mpgs . Not saying that will happen for you but I'm glad I did it . I had to make some brackets for linkage and return springs and such . ( I didn't buy the kits . Rambler mentality I guess )  If your car is already running good as you say it might just need a complete tune up . Ignition and carb .  Plenty of write ups on both .

[Draekon]

I tried a MC2150 for awhile. Could never get it set up quite right. Eventually went to a new Carter BBD and that helped tremendously.

[macdude443]

I tried the 2100.  It was pretty terrible.  I put on a dirty Carter and there was a night and day improvement.  Both my Eagles run the Carters and I've been averaging mid to high 20's in MPG.  The 2100 seems to be an upgrade that many recommend just as a rule, however.  The Carter gets a bad wrap because many don't know how to tune and rebuild it IMO.

[Vgrizzw]

Good to know...I was wondering if its really worth while and its good yet contradictory to hear both sides of the story.  There are so many posts praising the 2100 that it made me think that my car might not be running as good as I believe it is.  I haven't ran the numbers but I feel I'm getting at least 25 mpg, no stalls, perfect idle, and starts right up as long as it isn't dead cold.  I guess if it isn't broke, don't fix it.

[mo.eagles]

I agree , if your getting 25 mpg I would just go with complete tune up and even check valve adjustment . I know they are hydraulic lifters but there is an adjustment procedure .

[macdude443]

Good to know...I was wondering if its really worth while and its good yet contradictory to hear both sides of the story.  There are so many posts praising the 2100 that it made me think that my car might not be running as good as I believe it is.  I haven't ran the numbers but I feel I'm getting at least 25 mpg, no stalls, perfect idle, and starts right up as long as it isn't dead cold.  I guess if it isn't broke, don't fix it.

Yeah, I certainly wouldn't touch it.  Maybe a rebuild but I'd still wait for a significant problem first.  If you take a crusty, poorly running Carter and plop on a fresh 2100, you're surely going to notice a difference, lol.

[carnuck]

Silly question for those who did the MC2100 swap and had problems. Did you also do the ECM Test Bypass and/or GM HEI swap? If you did the HEI swap, did you run full 12 volts to the dist? My friend recently had this issue and a quick check showed he had only 9 volts to the coil.

[macdude443]

I changed to the HEI at the same time as I put the 2100 on.  Ran it straight from the solenoid 12V feed.  The resistor wire had been removed prior.  The HEI was still installed when I swapped the dirty Carter on and experienced a 180 in performance for the better.  I have since re-installed the original ignition from parts I gathered, mainly after being influenced by the stock cars at AMO and the fine performance it's given with my wagon.

[carnuck]

Did you test the voltage? The resistor wire goes to the "I" terminal and coil + at the same time. If you ran the in-cap coil, there is a ground strap inside that I have found missing on several aftermarket dists.

[macdude443]

I never thought to check it after it was installed.  Like I mentioned the car ran 100% better after switching carbs and it ran fine after that until I swapped back to the original ignition.  The bogging and sluggishness went away with the 2100 and no other changes.  It's possible the power valve was shot.  I couldn't find any numbers on it to work with.  I believe we tested the voltage when we installed the distributor but this was years ago and I don't recall.

[carnuck]

The Carter has no power valve