The Stovebolt Site Forums The Shop Area Engine Shop Langdon's Carbs performance issue

After messing with different older duel carb setups I bit the bullet and bought a pair of Carter/Weber's from Tom. I have them installed and they are idling well.

Problem: When I go for a test drive after a block of some hard acceleration and regular driving it will sputter and stall like it isn't getting enough fuel. I can reduce speed(it didn't like being in third really at all) and limp it home in second. It can't be my fuel pump, it is relatively new.

I did notice while tuning that hitting the throttle should cause the vacuum advance to turn the distributor. When I do it will barely turn it. Alot less from the other setups I had on there. I double checked the connection and I am on the correct port on the carb.

Also, while getting it to run the front carb would flood and shoot fuel out of the vent? dumping alot of fuel into the intake and caused the engine to stall. I adjusted the float a couple of times and it seemed to fix this. Did I adjust it too much that it would cause this condition?

1958 235, fenton intake and exhaust, pertronix converted dizzy

Thank you for all ideas and help!!!

Maybe you did adjust it too far and now your running out of gas when you get on it. Have you called Tom and told him whats happening?

I would suspect the pertronix myself, I have had horrible luck with them. I have the new one they sent me which is an entirely different design than the one I returned, which is suspicious to me. But I am afraid to install it the truck runs so well with points. And it didn't run so well with pertronix.

Baldy- No I haven't. I've been only able to work on the truck on the weekends.

Brokenhead- I have had the pertronix for 5+ years now with no problems. It was working just fine with the last carb setup, why would it crap out with a new carb swap?

yeah a lot of people use the pertronix with great success, I haven't. It would be like, why did the transmission start slipping after I changed axle bearings in the rear end? (that sort of thing.) all I am saying is it would be something to check...they are not exempt from failure any more than anything else.

Somehow I don't think a new carb should be flooding.

TRUCKERNIX- I would think so too. Some dirt may have held open the needle/float from my priming it. But even after clearing and cleaning fuel would intermittently shoot out of a hole located in the top of the secondary venturi. It would shoot from the front carb and hit the back of the valve cover.

I don't know that carb and I don't know what happens to the warranty after you take the top off.

I have known people who really like that setup.

I have heard nothing but good things about this carb setup. This is actually the first time I have heard of a problem. Him and patricks are pretty much stone pillars in this hobby. Just give him a call, he WILL make it right if there is a problem. And he is extremely qualified to give you the correct answer. I would start there.

Call Tom Langdon and see what he advises.

I have that set-up and it has been 100% reliable, with no adjustments needed.

How did you set up the choke?

I went through two new airtex fuel pumps before getting a good one.

I took some bad advice (from here) and tried a fuel pressure regulator (unnecessary with an original 4-7 psi fuel pump).

To be safe, I put on two fuel filters, one in the supply line and one at the input fitting on each carburetor.

The Pertronix unit seems an unlikely cause of the symptoms you descibe.
Why would it affect only one carb?
Why would it affect the vacuum advance?

I don't know why the pertronix would do that. all I know, is it has caused me incredible grief, and is very easy to check. As long as you aren't sittin alongside the road in a windy rainstorm. The fella stated it couldn't be the fuel pump as it is relatively new, which in itself is a poor assumption, I have seen too many "NEW" things fail. Also several people in the past have stated they saw virtually no difference with the vacuum advance connected or disconnected, I certainly can't tell the difference in mine. (I forgot to reconnect it once) I was just throwing that out there, it would be very easy to eliminate that as a problem. The general concensus is to call Tom Langdon, there is no doubt in my mind he will take care of him. There is no point to not just go to the top in this situation, he is a very nice man, and knows what he is talking about.

I fail to see how ruling out the pump is a poor assumption when it is relatively new and I am getting too much fuel to the carb. Fuel is shooting out of the vent hole onto the rear of the valve cover.

I'll try to get ahold of Tom as soon as I can.

if you had said, "it isn't the fuel pump because I am getting the proper pressure and volume", that would be one thing, but merely being "relatively new" doesn't mean it is working properly. Too much pressure is not working properly as well, not likely, but I have seen some bizarre things in my career, I had gas just pouring out of my carb, and I had virtually zero pressure, which turned out to be a little tiny piece of rust stuck in my relatively new fuel pump, with really relatively new fuel system consisting of every part from and including a brand new gas tank, hoses, lines, pump, filter, everything except for the filler neck which had a couple of rust flakes on it and apparently one less after a while since it got stuck in my fuel pump. That is why I say that.

What kind of choke set up?

What kind of fuel filter(s)?

Electric chokes on both carbs are hooked up and working. They open up after a short period of the key being in the on position.

I have a stock glass bowl fuel filter just before the tee that splits off to supply fuel to each carb.

"Sounds" like a bad carburetor.

Update: I double checked all the settings on the carbs. I basically just retuned from the start. The engine runs/revs, sitting still, just great. Now when putting it in gear and letting the clutch out it wants to stall and die. No power at all. When I am able to get it rolling it is sputtering and chugging. No power under load whatsoever. I have read this could be an electrical problem? What say ya'll?

What did Tom Langdon say? Perhaps you are shorting the ignition circuit through the chokes somehow, I am assuming that is all you have done electrically during the carb change. What is your battery voltage, pertronix quits at 5.3 volts according to their tech fella, a 12 volt system is probably 10.6, but you would have to call them. Do you have vacuum leaks? These intakes are kind of funky to seal, and here again I am assuming, but is this a whole new intake? I would really call Tom, if I am not mistaken he was an actual GOOD engineer at GM at some point in his career and really does know what he is talking about. However someone said he was at some big car event for the next few days, but I don't know this for a fact.

Apache,
If it were mine, at this point I would verify a good strong spark--capable of jumping at least 3/4 inch to ground.
Then I would try to drive it on 1 carb at a time by releasing the connecing linkage leaving one carb at idle.
Of course it won't run normally but it should run and drive on 1 good carb and probably not on the sick one.Then we can go to work on the problem.

I'd send a private e-mail to Carbking for any persistant carb issue.

disconnect the wires to the chokes and block them open, and see if it makes any difference? Because despite some of what I said, changing carburetors shouldn't really create an electrical problem. But you need to prove it before you discount it, at this point anyway.

Any updates???

Well I figured it out. I haven't had much time to work on the truck lately because of work, but finally I got to it. I was going to try one last thing before calling Tom and it did the trick.

My vacuum advance went bad. I don't understand how it was just fine before the carb swap and some how during or after it went bad. With out it advancing the timing the truck would not move. My replacement came this past week, I installed it today and what a world of difference.

I didn't think the advance was that important. I knew it was for fuel economy and what not, but I didn't think it made the difference between being able to drive and not being able. Anyone else experience this?

my experience with it, is that it made no discernible difference one way or the other whether the vacuum advance is operating or not. I drove around for I don't know how long with it disconnected completely. (not on purpose) As a matter of fact this is the first time I have heard of it affecting anything. But tis wonderful you figured it out. (the "tis" part is because christmas is coming) But then again, I'm not presently running any heat to the manifold. And haven't been for a year now, and it runs great.

I am also pleased that your problem has been lessened. If your vacuum advance had a leak in it, it might have caused vacuum-leak problems.

A vacuum advance might improve performance a little, and might improve gas mileage more than a little, but I agree with brokenhead that one is not necessary. Big GM trucks with the same gasoline engine used on smaller trucks came from the factory with no vacuum advance.

Thanks fellas!

I thought that the vacuum advance wasn't that crucial either because of the big trucks and other things I have heard. Could it just be with the Langdon setup/carbs that this is so?

When the diaphram in my vacuum advance went bad, my truck would not run worth a flip.

Just another data point. `Twas a stock `53 powerglide engine with a manual choke rochester.

kurt

If there was a leak in the vacuum advance unit, you'd have significant problems.