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1949 Plymouth SD goes *blaaaaah* when accelerating


Oliver Klozoff

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Been working on this problem for a while... well more my dad then me, haven't been able to get to the garage in a while. 

Rebuilt Stromberg BXVD3 carb, New fuel system sans pump, points rotor etc. Vac is good. Put a manual choke on... I forget what else...

Starts and idles perfectly but given throttle it bogs down. Cup your hand over the carb and revs fine. Pa thinks it just needs a new carb, thinks this one's "worn out and sucking air somehow" 

Any thoughts? 

Read my previous post about it giving me a hard time if you'd like...

 

Thanks! 

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That’s odd that you have that carb on a Plymouth. That’s normally on a Dodge with fluid drive. Try this test. With the engine running spray carb cleaner around the base of the carb. If the idle picks up there is a leak. It could be worn throttle shaft bushings or a leak at the base gasket. 

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3 hours ago, Doug&Deb said:

That’s odd that you have that carb on a Plymouth. That’s normally on a Dodge with fluid drive

 

Would this cause a problem on my engine? It's what the car came with. I also have the original carb, condition unknown. I'd have to rebuild it and test it. Fitment would require re-routing fuel lines. 

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I’m not sure about the bushings. I’ve never had to replace them. I don’t think that carb would cause your problem. It has a dash pot that you don’t need with the manual transmission. It might be worth while to rebuild the original carb although you have to wonder why it was pulled in the first place.

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On my older B&B carburetor there is a "power circuit" which handles the transition from idle up. It is actuated by manifold vacuum through a passage through the mounting flange. When it wasn't working the symptoms were similar to what you describe. If the mounting gasket for the carburetor is installed wrong then a small hole that provides the vacuum can be blocked.

 

I don't know if your Stromberg, or even later B&B carburetors have that. But if there is a small hole in the mounting flange of the carburetor there is likely supposed to be an equivalent hole on the gasket.

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If the power valve or step up isn't working it can ironically cause stumbles either from running too rich ( jet stays upen) or lean stumble (jet doesn't open).  Only difference rich fouls plugs, makes black smoke, and gives terrible fuel mileage like 8 mpg or less.

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4 hours ago, Plymouthy Adams said:

you cannot block the vacuum source

 

 

My Pa is on the phone right now, he said the manifold does NOT have any other holes for vac. Just the main intake hole. There IS however a hole on the Stromberg that was covered with the gasket we made. He also verified the Carter has a vac hole as well. He said earlier today it started and idled for about 20 mins and when he took the carb off it was pretty hot... vapor lock?

 

Also, spraying around the carb did cause an increase in rpm. Whether that's a bad gasket or bushings as mentioned above has yet to be determined.  

 

He has the Stromberg off now, and there was somehow water in it... idk how. We had drained the tank day one and replaced all the fuel lines. Will check the fuel bowl.

 

Pics of carbs and intake base:

https://imgur.com/a/45qdygm

 

One of yinz from western pa and not doing anything this weekend....? 

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Should we rebuild the Carter? 

 

Also, Pa mentioned an adapter and adding a 2b carb of some kind. Idk....

 

Is there a less costly carb option should we decide to completely replace the whole thing? So you think the Stromberg is workable?

Edited by Oliver Klozoff
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you quoted me wrong, you CAN block the intake....the statement was "be aware you cannot bock the vacuum source" and expect it to work"

 

sounds like you are not near the car, not doing the work and only reporting what is told without personal observations on your own. and the manner of most gaskets is that the manifold source is present by the very design of the gasket that does ensure no matter how you place the gasket the port on the carb base will be open to the manifold vacuum source...left, right, top, or bottom.  Now if you or your pa made the gasket without regard for the port...I have no clue  Look at your own pictures.  The outline of the original gasket is clear on the intake with the 4 open slots so no matter what position you place it the gasket will port manifold vacuum to the small hole in the base of your pictured carb.  Without that, you will not operate the power piston to enrichen the mix.  

Edited by Plymouthy Adams
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6 minutes ago, Plymouthy Adams said:

you quoted me wrong, you CAN block the intake....the statement was "be aware you cannot bock the vacuum source and expect it to work"

 

sounds like you are not near the car, not doing the work and only reporting what is told without personal observations on your own. and the manner of most gaskets is that the manifold source is present by the very design of the gasket that does insure no matter how you place the gasket the port on the carb base will be open to the manifold vacuum source...left, right, top, or bottom  Now if you or your pa made the gasket without regard for the port...I have no clue  Look at your own pictures.  The outline of the original gasket is clear on the intake with the 4 open slots so no matter what position you place it the gasket will port manifold vacuum to the small hole in the base of your pictured carb.  Without that, you will not operate the power piston to enrichen the mix.  

 

Ok I got you, idk the hole on the carb opened directly to the main intake ... thought you impled there was a second hole on the manifold. 

 

No I'm not there, the cars about an hour away at my parents, i can only get up there on the weekends and my dad isn't internet savvy enough to post here lol

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5 minutes ago, Doug&Deb said:

A bit north of me. Unfortunately I’m fighting a problem with my Dodge and that’s my weekend project or I’d be glad to help. Do you have access to another carb? Even if the linkage won’t hook up it might tell you something.

A quick jaunt up 79! Beers would be provided of course!  

 

Hes currently putting the Carter on, it's condition is unknown as it was just rolling around the trunk when I bought the car. Shouldn't take long lol

Edited by Oliver Klozoff
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1 minute ago, Plymouthy Adams said:

inform him please the gasket has to be thick original style that is slotted for the vacuum source....else..you are not installing properly and cannot expect different results even with original carb....the gasket must be correct.

 

How thick was the original gasket? Bc the kit came with a rather thin one. 

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