2V carb swap - runs like crap

[Anonymous]

I have a '65 Mustang coupe, 200 CID, 3 speed tranny. I purchased a remanuf Autolite 2100 carb from Advance Auto Parts on top of an adapter from Summit Racing. Bought a new throttle cable and used brackets which work fine. Even kept the same pedal and rod under the dash, with extensive modifications. But, I can't seem to get the carb tuned. No RPM guage, so not sure if idle is set right. Of the 2 screws on the bottom in front, the left screw has to be screwed out about 3 turns to get the car to idle at all. The right screw makes NO difference at all, screwed all the way in, or all the way out. Runs OK at idle - little miss. Runs terrible above idle. Vacuum advance was not working, but that is now changed. The car actually ran OK before the Vacuum advance was changed, but still wanted to die on takeoff. Timing is another issue. The mark on the harmonic balancer is off from timing marks, like 1/6 the circumference of the pulley - 1 cylinder. I put everything together right, all marks alligned. Ran good with the old 1 barrel on it for 3 months, with NO vacuum advance. Last day of driving with the 1 bbl, the car stalled. Had to hold to the floor to restart, and high RPM's to even move without the car dying. I baby'd her home. When it died, gas came back up through the carb. I wanted to upgrade the carb anyway. But, now I need help/advice to get my 65 moving again.

 

[simon]

hi and welcome on the board,

sounds like your setup is severely mis-tuned. I can think of many causes for your 2100 not performing anywhere near like the former 1bbl.

Vacuum leaks might be one, especially when using spacers and adaptors.

Concerning your 2bbl, purchasing a so-called "rebuilt" carburetor form any parts vendor is the proverbial luck of the draw. Usually, most carbs sold as "rebuild" units perform like they have been worked on by some ham-fisted winos in a back yard somewhere in Tijuana, and need another proper rebuild.

What sort of distributor are you running, anyway? Is it still the original 1965 vacuum-only-advanced "load-o-matic", recognizable by a d-shaped solid shaft, or is it a '68 or later dual-advance distributor?

 

[ludwig]

some ham-fisted winos in a back yard somewhere in Tijuana,

You saying that ham-fisted winos only live in TJ? For your information, we have ham fisted winos right here that can mess up a rebuilt carb too.

 

[Ferris Bueller]

Never has a carb been rebuilt by me successfully without someone else finishing the job. And I haven't had a drink in over a year.

 

[addo]

Drink of what? Berryman's carb cleaner? :roll:

 

[Anonymous]

Running stock load-o-matic single advance distributer, pertronix ignition, flamethrower coil.

 

[simon]

Running stock load-o-matic single advance distributer

not gonna be working properly with a 2100, which has no spark control valve.
SCV-controlled load-o-matic advances by venturi vacuum which your new two barrel carb cannot provide to your distributor.
No matter where your vac. line is connected to now, it means your timing is not advanced at any time you crack open the throttle.

first get yourself a 1968-up dual advance distributor (and some softer springs to experiment with later - Mr.Gasket part#925D).

second, a coil-triggered tach might be a good idea.

Did your car run well when the 1-barrel carb was still in place?
I suggest putting the old onebarrel back on, just for getting the timing and distributor dialled in correctly; as long as you don't know if your new "rebuilt" 2100 is really working like its supposed to.

Personally, when dealing with a questionable carb, I'd drain the gas from the 2100's bowl, remove the top, remove the venturi boosters and idle air screws and check every passage with compressed air. Keep in mind this might void your return warranty.

fourth, before you put the 2100 back on, rule out any vacuum leaks by either checking the surfaces of carb flange, spacer and/or adaptor for straightness, if you can't get the engine to idle at all. If it idles, check the questionable areas with an unlit propane torch or break cleaner (caution!)

 

[Lazy JW]

Running stock load-o-matic single advance distributer, pertronix ignition, flamethrower coil.

You need to be able to crawl before you can walk. If it won't idle well, that is the first thing to adress, and it likely won't idle well with that distributor on that carburetor. The load-o-matic requires a matching Spark Control Valve on the carburetor to send the proper vacuum signal. Without this it probably won't be able to be properly tuned. Maybe time to upgrade to a DS2?

Trying to tune an engine, especially one that has been modified, without the proper tools is really a good way to get frustrated. Beg, borrow, or buy a handheld tach, timing light, and a vacuum gauge. Learn how to use them and life will be a lot easier in your quest for performance.
Have fun,
Joe

 

[Anonymous]

I am getting vac advance when I crack the throttle now, verified with timing light.

I'll get the tach and vac guage too. Planned on it anyway.

Car ran well with 1 bbl installed, without vacuum advance working. I can put it back on for now to get it going again, BUT, why would it have started dying at takeoff when it was not doing it gefore?

I don't want to tear into the carb YET anyway. Never had much luck myself rebuilding, so I don't want to take any chances.

 

[Lazy JW]

I am getting vac advance when I crack the throttle now, verified with timing light...

Maybe so, but it won't be the correct value. The SCV sends a modified vacuum signal. The ported vacuum you have tapped into will give a vacuum roughly identical to manifold vacuum as soon as the throttle uncovers the vacuum port. This vacuum signal will be quite high at low throttle opening which will yank the vacuum advance in your Load-o-matic to maximum advance.

It really is important to have a distributor and carburetor that match.
Joe

 

[Anonymous]

I put a $39 rebuilt 68 distributor and used autolite 2100 on my 68 200 engine and she runs great.

Sounds like some passages in the carb may be dirty if the left idle screw does nothing.

Also timing could be off. Verify that and start at about 8-10 degrees BTDC.

 

[Anonymous]

Thanks for all the great information. I'll do some more work and let you know how it goes. Sounds like I just didn't know what I was doing with the upgrade.

 

[addo]

When I started messing around with the Fords, it was pre-internet and the same types of problem occurred. People would say "All you have to do is..." and when you went about it, soon became apparent the advice was very third-hand.

The 2100 is a pretty simple carb, but as the specific gravity of fuel has changed, I am somewhat skeptical of well-made older carbs ever being as (potentially) good as they once were. The change in fuel density would to my mind, particularly affect transitions in the fuel circuit.

I'm just saying this so you are aware that the endpoint may still be imperfect compared to EFI (we are so spoiled these days!)... The distributor will certainly benefit from being changed to a more ideal type to work with the carb, though.

Cheers, Adam.

 

[mikeyo]

If you have an idle mixture screw that won't make any change at all something is wrong with that carbs idle circuit (dirt?) would be my guess.
May not be all the problem, and I have learned the whole load-o-matic bit yet, but all the two and four barrel carbs I have rebuilt both idle screws responded to adjustment and both were set roughly the same.

 

[JackFish]

If the curb idle screw is in too much it will put the throttle plate up on the transfer circuit slot, leaving the idle mix screw useless.
It follows that that could mean that the idle mix is too lean or the timing is too retarded.
Or it's not being set under the right conditions.

 

[powerband]

There is a saying that Carburetor is French for "Don't F&$# with it" , as was previously noted - you should reference the original or a loaner carb to verify the carb itself is not at fault. I have two 5200 Holley/Weber's, one runs great and jetting changes makes subtle changes - the other one ALWAYS has a bog off idle. I've re-jetted , changed power and accel as well as flow testing and still bogs. I put the jets from the good running carb in it and it still bogs although the other one runs good with any jets.

Currently I've been working on an Old School 3 Holley / Offy 3X1 carb setup. with the original 1904's carbs . The Clifford built six has three clean - rebuilt and modified early Holleys. I tested them individually and only ran OK. two of them ran badly and I put "Rebuild" kits in them which stopped leaks but didn't help the performance at all. I bought three old Holleys on sleezbay (cheap) one ran great, other two not too good. The use in three carb setup shows up any faults like loose throttle shafts leaking vacuum and rich idle problems.

Powerband

 

[Anonymous]

Just trying to learn here, so can someone answer the question why my original 1 bbl started dying at take off, when all was well for 3 months? I do know it was running rich at the time of problems. Idled fine, and steady driving was OK. Just take off was a problem.

 

[JackFish]

It could be the accerator pump diaphragm, or a sticky enrichment valve.

 

[Lazy JW]

...The car actually ran OK before the Vacuum advance was changed, but still wanted to die on takeoff.....

....Ran good with the old 1 barrel on it for 3 months, with NO vacuum advance...

Lots of industrial engines such as tractors run fine with static timing set at some value BTDC and no additional running advance. They typically operate in a relatively narrow rpm range.

Our Ford sixes are a close cousin to those engines. No doubt yours was able to "get by" with no functional advance as long as you had a fair amount of initial advance dialed in.

Obviously, something changed. Did you "fix" the advance BEFORE swapping carbs? You may need to put the 1 barrel carb back on and correct the ignition problems before trying the 2-barrel.

I suspect you have multiple problems. Get the ignition sorted out first, then tackle the carbs.

Are you running points?
Joe

 

[Anonymous]

Running pertronix ignition with flamethrower coil. Swapped to a 68 dual advance distributor now, running much better, but still stalling on takeoff. Runs great at cruising speed, with good acceleration. Still have the air/fuel adj screw on the carb that does NOTHING when adjusted. Still haven't checked for vacuum leaks, but that's my next step.[/img]