1934 ford backfiring

[34 fordor owner]

I’ve been having a lot of help lately and figured I’d go ahead and let y’all know what how it has been going. I reset my float it was not set properly and was letting too much gas in. With this I set my idle mixture screws by screwing them in until it slows and then half turn out. Also the bad valve is continuing to give me trouble. When I get into second at low speed it backfires then when I get to a higher speed it stops. Like I was told when I first got it running, this engine is old and tired and could be rebuilt. Is it possible to this winter remove the bad valve and put a new one in? Not looking to completely rebuild as of now. Thank you all again for the help!

[34 fordor owner]

Here is a short video of the car going down the road and you can hear the backfiring.

https://youtube.com/shorts/E6duwD3MHQc?feature=share

[T Scott]

I drove a lot of cars in my early years with bad valves, particularly six cylinder stove bolt Chevies, and I don't remember backfiring problems. Got a lot of poof, poof, out the tailpipe and low power but no backfiring. I think you have an ignition issue. Not to say that you don't have a bad valve as well but if you have erratic spark, that will allow unburned fuel to enter the exhaust system and then get ignited. (backfire) If you have a burned (unlikely) intake valve or a stuck (possibly) intake valve then I would expect popping through the carburetor. This may have been discussed in prior posts. If so, I apologize but that's my thoughts.

[drolston]

A compression test will generally tell the tale on valves. Take all the plugs out and block the throttle open so the engine spins fastest and intake is unrestricted. Report back.

[petehoovie]

Originally Posted by drolston

Report back.

There WILL be a TEST!

[34 fordor owner]

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I have done a compression test in the past right before I got it running and the numbers were not great. Also this is what told me I had a stuck valve on cylinder #6. Got the valve unstuck and drove on it and now, a month later did another compression and numbers are still not the greatest.
1:42
2:47
3:50
4:40

5:40
6:50
7:45
8:40
(With all plugs out and throttle plates open)

This engine is probably very old and that sticky valve will continue to give me issues. Should be expected of an old used car.

[jimTN]

May not be a valve. You do have low comp. but it seems to be fairly uniform, no one way lower than the rest. You could have a bad sparkplug wire or a rotor in the dist. crossfiring which was not uncommon in worn, high mileage early Fords.

[drolston]

Well, that's pretty bad, but at least consistent and no dead cylinder. I don't think you have a bad valve. I had a '46 that was about that worn out and drove it daily for a year, adding a quart every hundred miles, - until a fraternity brother was too broke to put oil in it and threw a rod.



So, my recommendation would be to put Motor Honey in the crankcase and Marvel Mystery Oil in the gas to keep you going until you get a replacement engine built, or funds for an overhaul. I suspect the backfiring will clear up if you drive it often enough and hard enough with those additives.



You might check the timing. Start by very precisely adjusting the points, and then advance the setting on the distributor until it pings when accelerating hard in second gear; then back off one mark.

[Southtowns27]

Is it backfiring out the exhaust or out the carb? Have you checked the timing? Done a wet compression check?

[piewagn]

Originally Posted by 34 fordor owner

Here is a short video of the car going down the road and you can hear the backfiring.

https://youtube.com/shorts/E6duwD3MHQc?feature=share

Are you running a Holley 94 carb? I had issues backfiring and I found that the accelerator pump nozzle was not being secured by the cluster retainer that bridges the clusters to secure them. It supposed to simultaneously secure the accelerator nozzle. I was drawing un-metered fuel through the accelerator chamber bypassing the nozzle. I tweeked the retainer and installed a new seal and it fixed my issue. You may want to check that out...

[34 fordor owner]

It is backfiring through the carb. I have had the dome distributor that is on it fully rebuilt and timing set correctly as well as the coil rebuilt before starting it. Also it does have the Holley 94 on it. It has been rebuilt as well but plan on doing it again soon because the gaskets are wet with fuel. Just recently I had to take the top off and set the float right as it was not done so at the time of the rebuild. I have been periodically shooting MMO down the intake valve stem and putting some in the gas. I will go ahead tomorrow and put a little in the oil. Been trying to drive it a good bit each day and get it cleared up. Even if it does sound a little funny it’s a super fun and rewarding car to drive.

[kurt v]

Have you got the wires on the correct plugs?

[piewagn]

Originally Posted by 34 fordor owner

It is backfiring through the carb. I have had the dome distributor that is on it fully rebuilt and timing set correctly as well as the coil rebuilt before starting it. Also it does have the Holley 94 on it. It has been rebuilt as well but plan on doing it again soon because the gaskets are wet with fuel. Just recently I had to take the top off and set the float right as it was not done so at the time of the rebuild. I have been periodically shooting MMO down the intake valve stem and putting some in the gas. I will go ahead tomorrow and put a little in the oil. Been trying to drive it a good bit each day and get it cleared up. Even if it does sound a little funny it’s a super fun and rewarding car to drive.

Make sure to check that accelerator pump nozzle after you tighten the screws…

[34 fordor owner]

Originally Posted by piewagn

Make sure to check that accelerator pump nozzle after you tighten the screws…

Will do! I will also go back and double check my spark plug wires.

[B-O-B]

backfire thru the carb will blow a power valve

[34 fordor owner]

Originally Posted by B-O-B

backfire thru the carb will blow a power valve

Where can I get the carb rebuilt by someone who knows these carbs well? I drove it around the block this afternoon and came back and noticed all 3 gaskets from top to where it connects to the intake are weeping fuel more than normal. It would not hurt to have it rebuilt again. Thank you!