Carb Help needed please!

Fred K-OR

Fred K-OR

Well-known member
As some of you may know, I am the one that knows little about the finer workings of the old Model A. So I always have lots of questions.

Being bored in these winter months, I decided to try my hand and rebuilding an extra carb. Well I got all the main pieces I needed, upper and lower bodies and ordered new parts from one of the vendors and got everything put together. Put it in the old coupe, was surprised it started, but the old rig just did not run well at all.

The problems: 1) it is running to rich. Ruff running with black smoke out the tail pipe. Turn the GAV all the way in but does not make any difference. But I did find that I needed to put in the little fitting in the GAV hole. Put this fitting in, started it with the GAV all the way in and still the same problem
2) second problem is that when I take it out for a drive, when I press on the gas, the carb backfires and it almost quits. This does not make sense based on problem #1 above.

So what am I doing wrong? Do I have something plugged up somewhere? If so where" Do the upper and lower bodies I pickup up have a problem in them somewhere? I did use all new parts for all the things that can be changed in the carb. I was thinking that I should swap out the upper and lower bodies with a known good one. This may be my next step. Bought the new parts from one of the best suppliers in the industry. Please help this old bored guy.
 
Great to ask questions,!!! We all need to learn.Did you set the float.? What are your jet sizes? Are all passages clean? Do you have the jet in side the GAV ?do you have any books for specs?
 
I don't know how thorough you where in rebuilding the carburetor, but all brass plugs should be removed and the passageway cleaned, especially under the GAV needle. In most vendor carburetor kits, the jets are not the correct size. Before using they should be flow tested. Fuel float should be checked for leaks and set to the correct height.
 
jm29henry said:
Great to ask questions,!!! We all need to learn.Did you set the float.? What are your jet sizes? Are all passages clean? Do you have the jet in side the GAV ?do you have any books for specs?
Click to expand...

I did set or checked the float.
The jets were all new purchased from Brattons. So I assumed they were the correct sizes.(maybe this assumption is my problem). I tried to blow all passages out with air. I did put the jet inside the GAV.
So tried to do the things that I heard were the things to do. But somewhere I have not found the problem(s).
 
AL in NY said:
I don't know how thorough you where in rebuilding the carburetor, but all brass plugs should be removed and the passageway cleaned, especially under the GAV needle. In most vendor carburetor kits, the jets are not the correct size. Before using they should be flow tested. Fuel float should be checked for leaks and set to the correct height.
Click to expand...

I have not removed the brass plugs which in this case, maybe I should do being I purchased the upper and lower bodies and do not know what shape they are in. I did check and set the float valve for adjustment and float for leaks. But looks like I need to get into it more!
 
Jet Sizing-all old washers removed from jets including gav.No washer on idle jet!
 

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Fred K-OR said:
I did set or checked the float.
The jets were all new purchased from Brattons. So I assumed they were the correct sizes.(maybe this assumption is my problem). I tried to blow all passages out with air. I did put the jet inside the GAV.
So tried to do the things that I heard were the things to do. But somewhere I have not found the problem(s).
Click to expand...

New jets are not correctly sized and to be successful in the rebuild jets must be flow tested and appropriately resized to provide correct flow. Also if passages are not verified clear you will not be successful in your rebuild.
 
Gary WA said:
Jet Sizing-all old washers removed from jets including gav.No washer on idle jet!
Click to expand...
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Gary, looks like you have done a few carbs. I am still learning and have a lot to learn.

I think the first thing I need to do is make sure all the crud is out of the lower part of the carb. I saw a lot of rust in this part and thus I am thinking that some of the passages are plugged up.
 
Renners Corner sells the flow tested jets. They also have all necessary parts at a reasonable price. I would not drill out the brass plugs. Many carbs have been ruined doing that. I use a fine stainless wire to run through the passages and usually get all the rust and crud out. Good luck
 
AL in NY said:
I don't know how thorough you where in rebuilding the carburetor, but all brass plugs should be removed and the passageway cleaned, especially under the GAV needle. In most vendor carburetor kits, the jets are not the correct size. Before using they should be flow tested. Fuel float should be checked for leaks and set to the correct height.
Click to expand...

I wouldn't drill out and replace plugs. You run the risk of cracking the casting when forcing in new plugs. Not necessary. Glass bead the passages and run paper clips through the passages to check
 
Fred, if that bottom piece was very rusty, you might want to soak it for a day or two in some evapo-rust. It works great for removing rust. As stated earlier, get a piece of fine wire and run it thru all the orifices. That's what I always do when I rebuild them. I would not do any drilling on any of it unless absolutely necessary. Patience, patience. You will get it. Just my 2 1/2 cents. Good luck with it.
 
The problem is that a little too much gas is getting through as opposed to too little. Go through all of the fuel regulation parts of the carburetor, Float, float valve, jet sizes ETC. There are no mysteries in mechanics, only questions whose answers are not immediately obvious!
Terry
 
Hidden passage's need to be open, I believe Tom Eddy has talked written about this! Using a paper clip and bending to get through the passages. Following the step by step and you will successful in your rebuild :-)
 
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