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Old 10-06-2020, 02:10 PM   #1
durk
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Default 1941 convertible backfire to carb, with video

Hi,

I am from the Netherlands so sorry for my bad english.

i just bought a 1941 ford in america. The owner said it ran perfectly.
I think he and I have a different view on that.

The engine idles well. When I accelerate slowly, the engine also runs reasonably well. when I kick the gas I sometimes get a backfire or the engine throttles. It seems like the mixes are not right. or that he gets too much gasoline.
I've already turned the air nozzles and no response.
Below is a video. It is not very easy to hear.
If it is not good enough I can make another movie.

(the rattling is the license plate holder)

https://youtu.be/LPnzcfypPlU
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Old 10-06-2020, 02:23 PM   #2
drolston
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Default Re: 1941 convertible backfire to carb, with video

I would run a compression test to determine the overall health of the engine rings and valves. A sticking or worn intake valve can cause popping back through the carburetor.

How does the engine behave when driving?
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Old 10-06-2020, 02:27 PM   #3
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Default Re: 1941 convertible backfire to carb, with video

It's hard to say "exactly" what is going on even with your video.....I would check the vacuum line and make sure that it is solid and hooked up correctly, its seems like the timing isn't advancing when you accelerate?? You say that you have messed with the air mixture screws with NO results, that certainly is a problem!!! IF you are not getting any results from turning the mixture screws then at minimum the throttle shaft is worn and pulling air around the shaft. The timing seems okay as it starts quickly and seem to idle nicely.....I would look at the vacuum line to the distributor and make sure its solid and not compromised, then I would look at maybe sending the carburetor to Charlie (here on the barn CharlieNY) and having him rebuild your carburetor, then you have a more solid foundation to work from IF you continue to have problems!!!!

Last edited by rockfla; 10-06-2020 at 02:38 PM.
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Old 10-06-2020, 02:54 PM   #4
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Default Re: 1941 convertible backfire to carb, with video

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Originally Posted by rockfla View Post
It's hard to say "exactly" what is going on even with your video.....I would check the vacuum line and make sure that it is solid and hooked up correctly, its seems like the timing isn't advancing when you accelerate?? You say that you have messed with the air mixture screws with NO results, that certainly is a problem!!! IF you are not getting any results from turning the mixture screws then at minimum the throttle shaft is worn and pulling air around the shaft. The timing seems okay as it starts quickly and seem to idle nicely.....I would look at the vacuum line to the distributor and make sure its solid and not compromised, then I would look at maybe sending the carburetor to Charlie (here on the barn CharlieNY) and having him rebuild your carburetor, then you have a more solid foundation to work from IF you continue to have problems!!!!
sorry, that's because of the translation. I meant that the engine did not improve when I turned the air mixture screws.
When I turn it, the engine starts to spin faster or when I turn it off the engine stops.
It looks like a brand new carburettor.

I'll check the vacuum and compression tomorrow.
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Old 10-06-2020, 03:15 PM   #5
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Default Re: 1941 convertible backfire to carb, with video

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sorry, that's because of the translation. I meant that the engine did not improve when I turned the air mixture screws.
When I turn it, the engine starts to spin faster or when I turn it off the engine stops.
It looks like a brand new carburettor.

I'll check the vacuum and compression tomorrow.
Are you sure on what OR how to properly adjust the carburetor??? I meant its "Hard to tell" even from your video, not your English prowess!!!
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Old 10-06-2020, 04:50 PM   #6
mike d
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Default Re: 1941 convertible backfire to carb, with video

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Have you checked the fuel pump `output pressure . too high will cause problems!
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Old 10-06-2020, 06:18 PM   #7
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Default Re: 1941 convertible backfire to carb, with video

Check your accelerator pump setting and discharge .
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Old 10-07-2020, 05:11 AM   #8
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Default Re: 1941 convertible backfire to carb, with video

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Check your accelerator pump setting and discharge .
i dont know how...?

De feulpressure is 4,35 psi. (0,3 bar)
I connected a meter to the pump and started it for a few seconds.

https://www.mupload.nl/img/mh4pyiz6n.jpg
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Old 10-07-2020, 05:59 AM   #9
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Default Re: 1941 convertible backfire to carb, with video

The easiest first..spark plugs must not be sooty and be gapped at .025....I like Autolite 216's or a little hotter for tired motor ...437's. If the distributor was not set up
correctly , dwell most important, you can get that lag and pop. For sure the carb needs
help. If you have not joined the V8 CLUB think about doing that. There are many
great Flathead guys in the Netherlands. E mail me if you wish cas5845@yahoo.com
I can at least get you information about the V8 CLUB.
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Old 10-07-2020, 06:27 AM   #10
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Default Re: 1941 convertible backfire to carb, with video

way too much. should be around 2psi, you may need use an inline regulator
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Old 10-07-2020, 07:08 AM   #11
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Default Re: 1941 convertible backfire to carb, with video

Fuel pressure is too high 2 to 2-1/2. The high pressure will cause engine to flood with fuel, since the carburetor fuel shut off valve was not designed for the pressure you have.

Can you identify the carburetor. It appears to be a 94 look for more identifying numbers.
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Old 10-07-2020, 07:54 AM   #12
rockfla
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Default Re: 1941 convertible backfire to carb, with video

Durk
Many have posted here, ALL with good advice/counsel. Given ALL the "potential" suggestions, some by what I would call "experts"........You seem like you want to drive your car and enjoy it.......With that said, and I know it will take "extra" time being you're in the Netherlands.....and NOT a whole lot of extra money......but smart money & great insurance would say


Pull the fuel pump & carburetor and send it to ChalieNY.


Pull the distributor and send it to Mike at Third Gen Auto, 35fordTN here on the FordBarn



Let them BOTH work their magic on your components and you KNOW that all are in 100% working order and will be assured of having many enjoyable carefree hours of driving that fine 41 of yours!!!
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Old 10-08-2020, 02:02 PM   #13
durk
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Default Re: 1941 convertible backfire to carb, with video

just an update on this side of the ocean.

Thank you all for thinking along.
Good idea rock fla, but I want to try it myself first, if I can't I can send it indeed.
Terry, it is indeed a 94 I think.

I did the following today. I was allowed to borrow parts from someone with a well-running 1940 pickup.

I transferred the spark plugs, complete ignition, fuel pump and carburettor to my engine.

And guess what. Still the same problem.
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Old 10-08-2020, 02:46 PM   #14
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Default Re: 1941 convertible backfire to carb, with video

At this point, have you done a compression check on the motor??? What do your plugs look like???? AND I will say....at least on the distributor issue.......Just because its running good on an engine doesn't necessarily mean it's "right" as you "MAY BE" (obviously don't know that for sure) are experiencing????? Having the distributor set up on a machine, knowing the points and dwell are set in a "simulated" running condition, knowing it advances correctly.... removes ALL doubts!!! AS well as having a known good condenser!!! Just saying!!!!
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Old 10-08-2020, 02:58 PM   #15
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Default Re: 1941 convertible backfire to carb, with video

If you want to try your self Remove the carb and pull all the jets then blast it out (all the holes ) wth at least 100 psi of air ,prob the holes in the cast iron base with some copper wire ,
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Old 10-09-2020, 03:01 AM   #16
durk
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Default Re: 1941 convertible backfire to carb, with video

yes i did a compression test. I forgot to mention in my previous comment.
Compression is between 70 and 110 psi. (cold)

I understand your reaction that I don't know 100% that the ignition is perfect. But if one block runs well and the other continues to experience exactly the same problems, you can still say that the problem is not with the ignition.
I have placed my ignition on the 40er pickup and it runs perfectly.

It is so strange that the engine idles perfectly and at full throttle. And if you accelerate slowly, it's okay. And when you give full throttle from idle, the engine chokes.

does anyone have any ideas what I can check?

Last edited by durk; 10-09-2020 at 08:56 AM.
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Old 10-09-2020, 04:09 AM   #17
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Default Re: 1941 convertible backfire to carb, with video

Do you think you might have a lazy valve spring, or intermittently sticking valve? Swapping all the parts from a known good car eliminates all of those parts. All that is left is the base engine unit.

It drives ok if driven slowly or accelerating gently.

The only thing I can think of would be to put as many gentle miles as possible on it and see if it improves. You could try adding something to the fuel or directly down the carb, a locally available version of Marvel Mystery Oil. (I'd try auto trans fluid straight down the carb. be prepared for lots of smoke.)

If it is a sticking valve it will free up with use. It may have gone tight during the time taken during shipping and may have been ok when the previous owner had it. He may have only ever driven it gently and slowly.

Other than that I'm completely stumped.

Mart.
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Old 10-09-2020, 04:16 AM   #18
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Default Re: 1941 convertible backfire to carb, with video

Quote:
Originally Posted by durk View Post

It is so strange that the engine idles perfectly and at full throttle. And if you accelerate slowly, it's okay. And when you give full throttle from idle, the engine chokes.

does anyone have any ideas what I can check?
It sounds like the engine may be starving for fuel (not choking)
Try moving the accelerator pump adjustment to the outer hole if it is not there.
If there is an improvement, then the pump is faulty.
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Old 10-09-2020, 04:21 AM   #19
durk
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Default Re: 1941 convertible backfire to carb, with video

the car drives well indeed. if driven slowly or accelerating gently.

tried all 3 holes. no improvement unfortunately.
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Old 10-09-2020, 04:36 AM   #20
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Default Re: 1941 convertible backfire to carb, with video

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the car drives well indeed. if driven slowly or accelerating gently.

tried all 3 holes. no improvement unfortunately.
While trying to accelerate, did you pull the choke to see if there was any improvement?
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