1952 Pontiac Chieftain Carburetor Troubles

[MercMontMars]

Hi there, I have a 1952 Pontiac Chieftain with a swapped 1954 Pontiac Straight-8 as the original motor was blown (hole in the block.) Equipped with Hydra-matic transmission. I recently acquired the vehicle and have since done a lot to it, basically doing my best to remove the "previous owner syndrome." I was able to drive it to my shop but since it hadn't been up to temperature in at least 25 years multiple things failed such as the carburetor and the original fuel pump. I was amazed that this motor ran as it was because pretty much everything was beaten and neglected. 

 

But on to the problem. I had the carburetor rebuilt and I installed an Edelbrock 2-5psi electric fuel pump until I can rebuild the original mechanical one. Motor starts right up with the choke closed, I let it high idle to warm up then bring it down by tapping the gas. Everything looks and sounds good, but upon hitting the gas I hear a hiss from the carburetor and the motor dies if I keep my foot down. It will rev up if pushed up and down, but I can't drive the car like that. A couple observations I made is that the throttle linkage looks very rigged and it's always laboring the accelerator arm on the carb so the motor is never at true idle, idle screw isn't even making contact with the acc. arm. I forced it into place and the motor ran like a straight-8 should, smooth as butter. But I can't keep it there and still stall out after the carburetor makes a loud hiss on acceleration. 

 

It may be worth noting that the vehicle is still on a 6v system but I have it on a 12v battery w/ 12v coil for now just for cranking amps. I will run it on 6v once everything is tuned and running right, but the 6v batteries do not like partaking in turning the motor over again and again.

 

 

Sorry for the huge paragraph, I'm trying to be as descriptive as possible. I'm hoping that there is a Straight-8 specialist here or someone who might recognize my problem, as I've tried almost everything and nothing works. Healthy motor and runs great but I can't use it and it's very frustrating! I will upload videos of the issue when I can.

 

 

[Andy J]

You have your heat shield mounted wrong.Turn it over and put the angled part over the exhaust manifold.It should also have a hole in it that the heat tube from the manifold goes through.That may be your problem.Unscrew the heat tube from the choke control and just pull the tube out of the manifold.It shouldn't be fastened.

[Rusty_OToole]

Dealing with old lash up repairs is the worst. Sounds like you already diagnosed it. Suggest you start by putting everything back to factory spec starting with the carburetor and linkage.

A factory repair manual will be worth its weight in gold.

I would start by doing a compression test. If you have decent compression across the board go on and do a complete major tuneup starting with checking valve clearance if possible, then ignition, finally carburetor. You may need to get a kit and overhaul the carb. If you do this don't go by the sheet that comes with the kit, go by the factory manual.

I never have any luck throwing random parts at a problem. I either have to diagnose a specific problem or if the motor is messed up generally, go right back to basics and check everything.

It would be nice if some Pontiac expert could come up with some slick trick to fix everything in 2 seconds. But failing that, you will have to go thru and check everything  and fix whatever comes up bad. Be encouraged by the fact that if everything is right it will purr like a kitten, it has no choice.

[john hess]

I would open the cap on the carb front.. (2 Phillips screws) the metering valves are in there.... you are supposed to add a few drops of oil to them occasionally.... should say that on the cap. 

Also, check the function of your heat riser valve. exhaust manifold will have a small shaft through it. hopefully it turns.. it will have a small crescent moon shaped weight on the front. it should rotate about 90*

there is a spring on the other end of the shaft... (should be).. if not, and the shaft moves, you can roll the weight clockwise towards the block... this will manually place the riser valve in the warm engine position... lube all your linkages... the simple things make a big difference. check for intake manifold leaks.... that will make for difficult trouble shooting idle issues.... one thing at a time and keep us posted. 

 

 

[MercMontMars]

@Rusty_OToole Thanks for the reply! I haven’t done a compression test yet, but I definitely will. With what I’ve done so far though, I got to experience a glimpse of that straight-8 magic. When I forced the linkage into the proper position, the motor idled so smooth I thought I killed it. Could balance a dime on the thing! Old cars are so picky!

[MercMontMars]

@Andy J My mistake, thank you. It was installed that way when I bought the vehicle, says a lot about the previous owner. I’ve never had good luck with previous owner monkey work. Will install it properly and see if that makes a difference.

[MercMontMars]

@john hess Thanks for the reply John! I haven’t oiled that yet as I figured the carb rebuilder would, but I’ll oil it again just to be safe. Haven’t had a look at the heat riser valve yet, but definitely worth checking out. Thanks again!

[Rusty_OToole]

1 hour ago, MercMontMars said:

@Rusty_OToole Thanks for the reply! I haven’t done a compression test yet, but I definitely will. With what I’ve done so far though, I got to experience a glimpse of that straight-8 magic. When I forced the linkage into the proper position, the motor idled so smooth I thought I killed it. Could balance a dime on the thing! Old cars are so picky!

That is a good sign that there isn't much wrong. Hopefully, a few minor repairs will have everything put to rights.

[carbking]

That carburetor is complaining because of the aftermarket manual choke!

 

Those things COULD be made to marginally work, but everything had to be right.

 

The choke control cable needs to be an absolute straight line from the housing bracket to the choke arm; absolutely no play.

 

When applying the choke to start the engine, ALWAYS (I detest that word, but in this case it applies), push the foodfeet down to the floor, and then pull the choke.

 

Quite possible the choke linkage is interferring with the fast idle cam, causing the issues you mention with the throttle and idle. Not certain, but believe this may alleviate the hesitation/stall issue on acceleration.

 

Would highly suggest:

 

(1) redo the choke cable installation

 

OR

 

(2) refit the original automatic choke

 

Jon.

[Ben Bruce aka First Born]

What Jon said!   I would unhook the manual choke and see what happens.

 

  Ben

[carbking]

14 hours ago, john hess said:

I would open the cap on the carb front.. (2 Phillips screws) the metering valves are in there.... you are supposed to add a few drops of oil to them occasionally.... should say that on the cap. 

Also, check the function of your heat riser valve. exhaust manifold will have a small shaft through it. hopefully it turns.. it will have a small crescent moon shaped weight on the front. it should rotate about 90*

there is a spring on the other end of the shaft... (should be).. if not, and the shaft moves, you can roll the weight clockwise towards the block... this will manually place the riser valve in the warm engine position... lube all your linkages... the simple things make a big difference. check for intake manifold leaks.... that will make for difficult trouble shooting idle issues.... one thing at a time and keep us posted. 

 

 

You don't oil the valves!

 

The oil is to be applied to the "bearing surfaces" in the casting holding the intermediate shaft. The screw holes are open to the shaft. Simply removing the screws and dropping a few drops of oil once a month or so is sufficient. The casting cover itself does not need to be removed.

 

Jon

[roysboystoys]

While the carb is off , look inside the manifold to check if the exhaust has burned through the intake manifold.

I've run into three incidences of this.

[MercMontMars]

@carbking Wow, I had no idea! I figured with the age of the car that was normal, but clearly I’m mistaken. The carb was already hooked up with a manual style choke when I purchased it and was hooked up with a cheap cable kit. Do I need to buy an electric conversion choke? It is a Carter WCD carburetor.

[carbking]

Why not return it to the way Pontiac built it???

 

While original choke caps with the correct lettering are expensive (for car shows); replacement black caps (no lettering) with a reproduction spring are readily available, and relatively cheap.

 

Often, the choke stove in the manifold is burned through. If this is the case, quite easy to fabricate one:

 

Choke stove fabrication

 

I believe you had the carb rebuilt? Check with the carb rebuilder, perhaps he/she can return the choke to original.

 

As to an electric choke? I do NOT recommend using an electric choke with an auto transmission older than the late 1960's UNLESS you live close to Miami, San Diego, or Honolulu, or a similar climate.

 

Installing an electric choke on my wife's daily driver maybe 45 years ago was one of the 3 dumbest mistakes I have made in working on cars since 1959!

 

Jon

Edited March 23, 2023 by carbking (see edit history)

[Bloo]

3 hours ago, roysboystoys said:

While the carb is off , look inside the manifold to check if the exhaust has burned through the intake manifold.

I've run into three incidences of this.

This is a very common problem with Flathead Pontiacs, and a lot of trouble could be saved if more people knew about it. I don't believe it applies to @MercMontMars car though because it has a 2-barrel carb. 1-barrel cars have a replaceable tube in there. On a recent Flathead Pontiac Zoom call, the subject came up once again and the consensus was that 2 barrel manifolds are not built that way.

 

MercMontMars: Look down the two throttle bores in the manifold with a bright light. What you are looking for is pinholes through the bores going toward the outside. The bores are surrounded by exhaust. I don't think you'll find any holes because I think it is all cast iron on a 2 barrel manifold, but it can't hurt to have a close look while the carburetor is off. Those bores were replaceable steel tubing on the 1 barrel cars.

4 hours ago, carbking said:

That carburetor is complaining because of the aftermarket manual choke!

Amen. Those are conversion kits are horrible.

1 hour ago, MercMontMars said:

Do I need to buy an electric conversion choke?

I suspect I know what @carbking is going to say here, but I'll wait and see. In my opinion what you need is the original part. The black plastic piece is what needs replacing. The right one will have a thermostatic spring inside. With the black thing removed, there is a little piston inside the housing. It must be free to move with the linkage. Start soaking it in penetrating oil if it is stuck. There might or might not be a fine brass screen where the hot air comes in from the little tube.

 

EDIT: I see @carbking responded while I was typing. A burned through choke stove, while a common problem on many cars, won't be a problem on this one. It is very hard to see how the flathead Pontiac choke stove is built while the exhaust manifold is still on the car, so I think you'll have to take my word for it. The exhaust manifold, despite it's looks, is a rams horn design, and the spot that little tube goes to has nothing but hot air.

 

What you DON'T want is the choke sucking exhaust through the little tube. The little tube is for hot air only. The little tube looks like it goes to exhaust on this car but it does not. Be careful with that little tube. It's super easy to break. It can be replaced, but that's just more work....

Edited March 23, 2023 by Bloo (see edit history)

[MercMontMars]

50 minutes ago, carbking said:

Why not return it to the way Pontiac built it???

 

While original choke caps with the correct lettering are expensive (for car shows); replacement black caps (no lettering) with a reproduction spring are readily available, and relatively cheap.

 

That’s my goal, I’m just slowly fixing all the knuckle-headed “repairs” done by previous owners. This is my first flathead straight-8 and it’s sometimes hard to tell what’s rigged and what’s factory. I have the original, or what I think to be the original choke cap and it has lettering on it that reads “General Motors, Rich< >Lean.” 
 

I’m assuming it wasn’t doing it’s job if someone rigged it so ridiculously with a manual choke and everything, so I’ll try getting a new one to see if that helps. 

[Oldtech]

Going back to the original dilemma, Two things come to mind. 1. Check the ignition timing. late spark could aggravate the issue. 2. Look down the carb and work the throttle and make sure the accelerator pump is squirting - in both barrels.

[carbking]

3 hours ago, MercMontMars said:

@carbking Wow, I had no idea! I figured with the age of the car that was normal, but clearly I’m mistaken. The carb was already hooked up with a manual style choke when I purchased it and was hooked up with a cheap cable kit. Do I need to buy an electric conversion choke? It is a Carter WCD carburetor.

If you wish to learn more about automatic chokes:

 

Automatic chokes

 

Jon

[Rusty_OToole]

The choke cap has a bimetallic spring inside that opens and closes the choke. They weaken over time and don't work right. If the one you have is the original best replace it as Carbking says. It may no longer be strong enough to do the job.

[MercMontMars]

@Oldtech Will definitely time motor better when I have it running, I know for sure it is off but with all the carb issues it’s hard to accurately do this. Carb is squirting as it should, I had it rebuilt so that is all good there. Thank you for the reply!

[MercMontMars]

@john hess Yup, I’ve found the crescent moon shaped weight. It rotates freely and returns to its position via a spring/coil. What does this do? First time I’ve dealt with one.

[Bloo]

That sounds like it probably works. There's a flapper in there that changes the direction of the exhaust. When cold, it brings hot exhaust up around the bores under your carburetor. When the manifold gets hot, the bimetal spring relaxes and the weight falls down and holds the flapper in a different position. Then the exhaust goes straight out.

 

 

[MercMontMars]

@carbking You were definitely right about the choke being wrong! I removed the cheap aftermarket cap and it’s all wrong.. thankfully the internal piston mechanism is still there but I unfortunately do not have the original spring driven cap and I’m having a hard time finding it. I will let you know what happens once I install the right part. I could put a universal one in but it’s a very shallow fit, I need a Carter WCD specific one. 

[MercMontMars]

I have this but it’s off of an 80s Rochester carb and doesn’t fit quite right. I assume this coil type mechanism is what I’m needing. Am I looking at it wrong and a universal one will infact fit? Sorry for all the questions, this is the oldest car I’ve worked on and there are so many previous owner rigs it’s driving me nuts!

[Oldtech]

What you have there is the conversion part for the ORileys or whoever, manual choke conversion. Yes you need the correct unit with the spring.  Early automatic chokes were a royal pain in the winter up here in the cold country and I got pretty good at fixing / modifying them to work. Most anyway.  Quite a few old timers went with these conversions instead of following through with getting the automatic to work.  Some factory ideas just didn't work in this country. Like the mid 70's ford ones with the electric that didn't cut in until the choke hit 50 degrees or so.  If you didn't let the vehicle warm up and headed for town at -35, it NEVER got to 50 around the carb and the choke never came off.  Cure was to pry the pins out and toss the bimetal. then it would work.  ( off topic... I know)

Edited March 25, 2023 by Oldtech (see edit history)

[Rusty_OToole]

The coil is a bimetallic spring. It is made of 2 different metals laminated together. The 2 metals expand at different rates when heated up. This makes the spring expand when it gets hot and tighten up when it cools off.

So, the spring closes the choke when cold and opens it when hot. Over the years the spring loses its tension , sags and doesn't work so well anymore so it pays to get a new one.

Adjust it so it closes the choke when the engine is cold and check that it opens completely when the engine warms up. The pipe feeds hot air from the exhaust manifold.

The choke is supposed to open slightly as soon as the motor starts, then gradually open all the way as it warms up. The choke also affects the fast idle adjustment.

Normal starting procedure is to press the gas pedal to the floor to set the choke then turn the key and start up the motor. It should run at a fast idle. After a minute you can pump the gas to release the fast idle adjustment and the idle should slow down.

[carbking]

There are universal choke cap/spring units readily available for Carter; you are simply looking in the wrong places. The one you picture will not work on your carburetor.

 

The original MIGHT be available as well, but probably no need to spend the money for it unless you plan to show the car.

 

While you are looking for the cap/spring, make sure the vacuum piston is not stuck, and the vacuum passage behind the piston is not clogged.

 

Jon

[john hess]

On 3/23/2023 at 10:03 AM, carbking said:

You don't oil the valves!

 

The oil is to be applied to the "bearing surfaces" in the casting holding the intermediate shaft. The screw holes are open to the shaft. Simply removing the screws and dropping a few drops of oil once a month or so is sufficient. The casting cover itself does not need to be removed.

 

Jon

that what I meant.... late night replies sometimes get misinterpreted...

[carbking]

1 hour ago, john hess said:

that what I meant.... late night replies sometimes get misinterpreted...

One of these days, in addition to "spell checker", Microsoft will institute "thought checker" where the software will read our mind and make sure we post what we are thinking!  Well, maybe not such a good idea  

 

Late night posts are the "Monday mornings" of the internet!

 

Jon

Edited March 25, 2023 by carbking (see edit history)

[auburnseeker]

Well google and several other services already have thought checker.  They remove any post they don't agree with or throttle it down so no one sees it.  Problem is when one person who always thinks they are right,  prevents others from being heard, mistakes and out right lies are presented as fact and since it's the only information allowed even if incomplete it becomes the truth and in some situations can be down right dangerous.   Since it then becomes the framework for future ideas and research, everything from then on will be flawed. 

[john hess]

4 hours ago, carbking said:

One of these days, in addition to "spell checker", Microsoft will institute "thought checker" where the software will read our mind and make sure we post what we are thinking!  Well, maybe not such a good idea  

 

Late night posts are the "Monday mornings" of the internet!

 

Jon

my wife already has that feature.!

[rocketraider]

9 hours ago, carbking said:

One of these days, in addition to "spell checker", Microsoft will institute "thought checker" where the software will read our mind and make sure we post what we are thinking!  Well, maybe not such a good idea  

 

Late night posts are the "Monday mornings" of the internet!

 

Jon

I can't even get the thing to understand a Piedmont Vajenya accent when using talk-to-text. I'd hate to see how it would mangle my thoughts.

 

On 3/22/2023 at 8:27 PM, MercMontMars said:

@Andy J My mistake, thank you. It was installed that way when I bought the vehicle, says a lot about the previous owner. I’ve never had good luck with previous owner monkey work. Will install it properly and see if that makes a difference.

Previous Owners Stamp is the bane of every old car owner. I think there's a special farm where these people learn car repair.

[60FlatTop]

20 hours ago, carbking said:

Microsoft will institute "thought checker" where the software will read our mind and make sure we post what we are thinking!  Well, maybe not such a good idea  

I have worked on punch presses that had safety recoil wrist bands that pulled your hands back each time the machine stamped. A system like that set up on the arms of my computer chair....

 

Auto spell and auto fill keep getting me. Ah, for the good old days in Salem where spell checker really meant something.

[JACK M]

An interesting segment on the Today Show a few days ago about AI. (Artificial Intelligence)

Now that the net has been around for a couple of decades, the clouds have gathered all this information and can make generalized (and fairly well documented) decisions about just about anything.

Will the computers take over some day? Kinda scary.

I think they should be banned and let us all go back to the good ol' days.

This morning it was pointed out that 'Tic-Tok' is WAY LIMITED in China.

A whole nuther issue.

Did I say that?

[rocketraider]

Reckon this AI nonsense will be able to diagnose our old car ailments and tell us how to make the repair? Even better find the parts at a reasonable price?

 

Oh, the possibilities...