1938 Special carburetor

[Guest 49340]

Hello to all.  I bought a 1938 Special about nine months ago.  The person who owned it before me started a nice restoration but then apparently did a hurry up job to finish reassembly.  There were many loose connections with the wiring, a master cylinder that needed replaced, brakes to be adjusted, etc.  When it ran, it ran great but quite rich.  My mechanic who has over 40 years of experience and is familiar with carburetors has worked diligently on the problem.  Two rebuilt carbs were bought from Carb X.  Neither of them lived up to expectation and did not work as advertised.  My mechanic rebuilt the existing carburetor, got the choke working perfectly, and so on.  The car starts and runs beautifully with none of the "running rich" problems experienced before nor the leaking problems it had before.  We are still, however, having issues with the way it loses power under acceleration on the road.  What I really want to do is replace the existing Stromberg with the same model carburetor which was why I bought and regretted doing so from Carb X.  Basically, that is what I want to do.  I want to replace the carburetor.  The car has an almost new gas tank, cleaned fuel lines, and a rebuilt fuel pump from Bob's Automobilia.  The old carburetor is the last thing that I will attempt to fix or replace before deciding to get rid of the car.  I had a 1937 while in college and loved it.  I am now 71 and bought this car to enjoy.  I has been on the road so little that I am not enjoying owning it.  She is a beauty but not very road worthy right now.

[LAS VEGAS DAVE]

I also have a 38 and am thinking that maybe the problem lies elsewhere. The carb is just so simple other than the choke that its hard for me to me to think that its the problem. Is the float level adjust to the level of the brass plug on the side of the float chamber? Have you ever taken a compression test? Is the timing correct? Does the advance work? When you say it loses power under acceleration the only thing that can cause that as far as the carb is concerned is a bad or improperly adjusted  accelerator pump or a low float level. Other things not carb related can also cause lack of power. If it was my car and the compression test showed good compression on each cylinder I would not worry about it will run fine after its tuned PROPERLY. If the compression test is not so good then no matter how well it is tuned it will never be like what it should be. I have two more GOOD carbs but they would be expensive and I believe a waste of your money.

Dave

[pont35cpe]

49340, makes me think the power valve/metering rods in the carb. not operating properly, or the dist. vac. advance and/or the 3 ball bearings(pivot points of breaker plate)in a bind/worn groove/dirty old grease, which would affect the spark advance.. All equal no power under acceleration.

[Mark Shaw]

I suggest you verify that your mechanic adjusted the timing correctly, and checked the distributor bearings and vacuum advance are working correctly.  Running with a retarded spark will seem like the carb is not working right.

[1939_Buick]

The other thread on this topic http://forums.aaca.org/topic/291546-1938-buick-special-40-carburetor/

 

[JRHaelig]

In the world of Ford flatheads we see symptoms like this and say that if it seems to be fuel related it's probably electric.

Then we look at coil first, condenser second.

 

Could you consider that as well?

[carbking]

Like everyone else posting here, I really don't think it is the carburetor based on the information you have given.

 

But for the sake of argument, lets say the carb is at fault.

 

The first through 10th items I would check on the carb would be the choke!!!!! I read your post that it is working perfectly. I have been doing carburetors professionally for almost 50 years, and I have yet to see a 1938 Buick with the original choke that functioned perfectly. Even Buick techs could not get them to work in 1938!!!!! Which is exactly why in 1939 Buick REQUESTED both Carter and Stromberg to produce replacement carburetors for the 1937 and 1938 Buicks WHICH WERE ACTUALLY SOLD IN BUICK DEALERSHIPS! And why 1937 and 1938 Buick carbs are so rare today, most of them were thrown away in 1939!!!!! And if the choke is not opening completely you WILL lose power above a certain RPM.

 

OK, I am wrong, and your choke is actually functioning perfectly. What else in the carburetor can cause your issue?

 

Losing power under acceleration can be two different issues:

 

(1) hesitation under initial acceleration and then then engine picks up normally (most likely cause vacuum advance in distributor, possible accelerator pump issue, possible power bypass jet and pump bypass jet in carb interchanged (same shape, same thread).

 

(2) engine accelerates to a certain RPM and just won't do more (if carburetor, low float setting, wrong main metering jet, power bypass jet and pump bypass jet interchanged, vacuum piston incorrect (wrong length) or stuck, no vacuum to vacuum piston (cheap generic rebuilding kit with incorrect gasket).

 

I also read that you have a rebuilt fuel pump. Did you do a pressure test and a volume test? If the fuel pump is faulty (remember, you got two faulty rebuilt carburetors) then the carburetor fuel level could drop causing a loss of power.

 

And finally (and I have factory documentation on my next statement): In the early 1950's, Carter had 1000 cars with "professionally diagnosed carburetor issues" brought to their factory in St. Louis. Approximately 3 percent were low compression, 93 percent were ignition, and 4 percent were actually carburetor related.

 

The car is gorgeous, and I can certainly understand your wishing to drive it. Stay with the diagnosis, and be prepared for the culprit to be something very simple that has somehow been overlooked (at least that is what normally happens to me)

 

Jon.

[Mark Shaw]

If you are still hell-bent on replacing the carb, here's one for you:  Yes is is for a Chrysler, but all the internals should interchange...

 

https://portland.craigslist.org/mlt/pts/6062584815.html

 

Edited April 18, 2017 by Mark Shaw (see edit history)

[LAS VEGAS DAVE]

The first thing I do when I get a new car or motorcycle is take a compression test. Without knowing how good or how bad the compression is its crazy to start blaming anything. I'm always surprised by the number of people that do not do that simple test. If you put a brand new out of the box fuel pump, carb, distributor and spark plugs in a car with compression that is to low or all over the place the motor will still have no power or run bad. A vacuum test is also a good test but I prefer the compression test to start with. As an example when we first got our car it had one low cylinder, adding oil to the top the piston on that cylinder bought the compression back up to the others. I suspected it had a stuck ring from sitting. It took a number of days with different oils (SEA FOAM, MARVEL, AUTOMATIC TRANS, ETC) to unstick it but eventually it worked and is now even with the others. Its always easy to blame the carb or ignition but in order for a valid diagnosis to be made the compression must be known. The fear of taking the head off to do a valve job or even worse to remove the motor to replace pistons or rings keeps many from taking a compression test but its the only way to know how to proceed on a motor that is not running good.

Edited April 17, 2017 by LAS VEGAS DAVE (see edit history)

[pont35cpe]

53 minutes ago, Mark Shaw said:

If you are still hell-bent on replacing the carb, here's one for you:

 

https://portland.craigslist.org/mlt/pts/6062584815.html

 

Mark, isn`t the `38 Buick carb. a 3 bolt with the starter switch in the base?

[carbking]

Mark - that one resembles a Chrysler.

 

Jon.

[LAS VEGAS DAVE]

That one is not like the one in my 38 Buick.

 

[DonMicheletti]

The Special carb has only 3 bolts

[Guest 49340]

I appreciate all of the replies.  This thing has driven me nuts for about 5 months, and I am running out of patience.  I think that unless some miracle happens the car is going to go up for sale.  I am going on 72 years of age and do not wish to spend whatever time I have remaining on this car.  It took me 47 years to buy a replacement for my 1937 Buick which was a basket case, sort of, but ran like a champ.

[pont35cpe]

49340, that`s way too nice of a car to give up on.. I think you need to check out the distributor vac. advance and the pivot points of the breaker plate. If it`s never been cleaned, dried dirty old grease at the pivot balls/groove could be the problem. Your old `37 and that big back seat area probably has some memories of your younger years..

[Guest 49340]

The distributor and all electrical components of the engine were worked on, checked, and in good order.  This car has been an enigma wrapped in a mystery.  When first bought, it ran rich.  Over a short period of time, the master cylinder began locking up the brakes after short drives.  Master cylinder replaced.  Brakes work well.  After driving the car with the master cylinder fixed and knowing it would stop and the brakes not lock up, the carburetor began leaking.  Gas came out the needle valves, throttle linkage, etc.  It leaked everywhere.  The gas tank was replaced by the previous owner but Sea Foam was put in to help clear things out.  I am guessing that lead to the blocked sediment bowl on the fuel pump.  Somebody put a 1939 fuel pump on this car before I got it.  A replacement fuel pump was installed.  After cleaning and rebuilding the original carburetor (prior to the new fuel pump), the car started and ran well at idle.  The automatic choke did what it was supposed to do thanks to my mechanic.  Yes, the choke is working fine now.  The car did not have any power on the road and acted gas starved, hence the new fuel pump.  The old pump was loaded with all kinds of junk which must have come out of the tank and lines.  The car starts and runs with the new fuel pump, but the carburetor started leaking around the gaskets.  I do not want to put another 5 months of my life and money into this car.  I would gladly buy a rebuilt Stromberg AVV-1 for it or replace it with a different type of carburetor and adapter plate.  I cannot find either of these.

[West Peterson]

49340

I hope you don't give up. I suspect that if you reveal your location, we could help you find someone in your area to give you some help.

[LAS VEGAS DAVE]

 I would recommend you try a fuel pressure regulator which is obtainable from Summit. I run one on my car after rebuilding the fuel pump and it stopped the same problem you are having. You probably don't need a carb. I spent the last two years searching for original carbs that were complete and found and purchased two of them. I spent much time and money on them so I have two spares. I tested each one on my car including the chokes and they both work fine. I would part with one but I'm fine with just keeping them for spares, they are hard to get. If you come to the point where you or your mechanic think you need a new carb contact me.

[jeff]

Don't be discouraged!  To me, it sounds like you have made great progress on many fronts.  Let us know where you are located, perhaps there is someone in your area.

 

I agree with the comments on ignition advance.  Sounds like that is worth a look.

 

Your fuel delivery issues (tank, lines, sediment, pump replacement...) all sound good - one thing I didn't see mentioned was the float.  Two issues could have been at play - sediment keeping the float needle valve from closing, or a leaking (sinking) float.  Both would give you a rich condition, with the car spitting and coughing.  These might have been corrected when your carb was rebuilt. 

 

I didn't see where you mentioned which carb is on the car now - of course, if someone put an inappropriate carb on there, that could be an issue.

 

If you replace your carb, you may want to consider a Stromberg AAV-167.  It was the recommended replacement for the AAV1, and I believe it is what the dealer would have installed on your car if it came back in in the early '40's.  Gives you a better choke arrangement.

 

Keep the discussion going - we'll get you through this.

 

Jeff

[MCHinson]

49340,

 

Welcome to the AACA Discussion Forum. In the discussion in the General Forum, you had several people give you some excellent advice, just as you have in this discussion. It is difficult to diagnose the problem over the internet without seeing the symptoms in person. If you have tried multiple carburetors, I suspect that it is something relatively simple that your mechanic is overlooking in the ignition system. I would suggest going over the ignition system carefully. I would make sure you recheck the point gap. I would change the condensor. It is not unheard of to find a new cheap foreign condensor to be defective out of the box. Change the coil, preferably with a known good working coil. On the ignition circuit, make the changes one at a time so you can identify what part fixes it when the problem is finally solved. 

 

If it is fuel related, I would suspect you need a fuel pressure regulator. I don't recall the proper pressure but off the top of my head I think it is something around 3 or 3 1/2 psi. I am sure someone will chime in with it. I would also make sure that the fuel lines are all clear. Is it possible that the fuel lines are full of gunk from the old tank? Unless you have changed the fuel lines or checked them, they could be suspect. If they are full of junk, your new fuel pump may also be full of junk now. 

 

After going through all of that step by step, then contact Las Vegas Dave and buy one of his spare carburetors if none of the cheaper and more common issues solves the problem. 

 

Most carburetor problems ARE electrical. I have been helping a friend work on a 1937 Ford recently and we were convinced that it was a fuel problem. After we eliminated all of the fuel supply system, we finally got around to fixing the electrical problem that was causing the issue with that car.