41 Ford rough running, backfiring, and hard engine vibration

[30aadoodlebug]

So I'm at wits end with this car. Two good rebuilt carbs, 2 different good distributors. New Vacuum lines, voltage regulator and it still runs like crap. Im running duals, and I get a little smoke out the left pipe no matter how rich or lean the carb is adjusted. Engine is vibrating like crazy at idle, and when I first start the car cold, I often only run on four cylinders. I have the idle backed all the way off, and shes still running high.

Im at a loss here. I'm hoping its not a valve issue. I did notice that one of the wires going to the ignition switch is hanging on by only a few strands.

any help would be appreciated

[Ggmac]

Lets start .
Have you taken a compression test ?
Correct firing order ?
Plugs new and gapped ?
Are the four that running on one side or 2 on one side and 2 on the other ?
What carb ? Any adapters ?
What distributor? 6 or 12 volts ?
Have you used a vacuum gauge , if so whats the reading ? Is it steady needle ?
More to come , but basics are needed
Sounds like a vacuum leak .
What year or version of the flathead ?

[30aadoodlebug]

new plugs. correct firing order. holly 94. 11a crab distributor with after market coil set up. its a rebuilt engine from 5 years ago with less than 3000 miles on it. its a late 41 pencil block. I have not done a vacuum test on the plugs yet.

[Anteek29]

I'd focus on both a vacuum test and a compression test...let us know.

[cadillac512]

Quote: "Engine is vibrating like crazy at idle, and when I first start the car cold, I often only run on four cylinders. I have the idle backed all the way off, and shes still running high."


This REALLY sounds like a vacuum leak...and a fairly large one at that. Look at all the intake manifold vacuum ports,the intake manifold gasket (even if you have to remove the intake) and maybe spray carb cleaner around the sealing surfaces of the intake and carb with the engine idling. You'll hear the leak and the engine will smooth out if you find one.



Terry

[Veeder]

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I suggest you take another look at the firing order in fact install a new distributor cap on that side or swap them. Firing order is easy to screw up on this distributor. I have a brother who lives in Carlisle so if you want a second set of eyes on it for a quick look let me know. I think I know the 11A distributor fairly well

[Ggmac]

Is it 2 cyl on one side and 2 on the other ? Important
Compression?
What coil mods ? If too much spark , it can arc inside the cap .
Aluminum intake or cast iron ?
Do your windshield wipers work? If not , remove and plug vacuum line , if yes , temporarily remove and plug vacuum line .

[30aadoodlebug]

Definitely a huge vacuum issue. I plugged the vacuum hose to the wiper and she's leveled out. This was a perfectly running and driving car three weeks ago. The firing order is correct. I triple checked it. my gut tells me its in the engine and hopefully the intake manifold. I have another one, and plan to make the switch this weekend. stay tuned. also, I am rebuilding the wiper motor, and have an nos 41 wiper switch to put into the car as well.

[Phil Gillespie]

Having a vaccum gauge fitted at dash gauges can certainly assist with many engine running fauts including your present ;hicup".
Phil NZ

[supereal]

Double check that the spark plug cables are in the correct position. Swapping plug wires can produce that problem. If they are correct, it is possible that one or more wires are shorting inside the metal conduits between the distributor and the plugs. Use an ohmmeter on each cable to see if the inner conductor is broken. This this can be true if the conductors are non-metallic carbon type. If they check out, inspect the inside of the distributor cap for evidence of one or more cracks or carbon paths.

[Ggmac]

Does it have a PCV valve installed?
I do love the 41 fords .
Good luck