Only running on 2 & 3

[Fast31]

A fellow Model A club member asked me to help him. Before I go over to his place I would like to get some input from you guy's. He recently bought a restored roadster from the US with lots of options added. It is only running on the second and third cylinder. It has a high compression head and the owner suspects it also has a "hot" cam. It came with a downdraft manifold with two Strombergs which is now replaced by the original intake and the Zenith. This did not cure the problem. It also came with a Mallory ignition which is also replaced by an original one, which also did not help. The car came with a box full off spark plugs and some Strombergs, which might be an indication the last owner struggled too. The owner tells me all cylinders seem to have the same and a healthy compression when he cranks it over by hand. I want to start with a leakage test. Any suggestions?

[Mike V. Florida]

Welcome, and you are on the right track with the leakage test. What is being used for a distributor and does he have spark to all 4?

[Fast31]

Thanks for your reply. It came with a aftermarket modern Mallory distributor. It has now the original Model A distributor. This swap did not cure the problem. All 4 plugs spark.

[100IH]

Model A's don't often have problems with firing order because of the original cap has the order built in to it . Since you have a Mallory distributor, you must have the more common cap and wires. Know that the order is 1-2-4-3 in a counter clockwise rotation. I agree that you should do your own compression and leak down test. Any distributor cap could have issues that can cause misfire. Good Luck.

[100IH]

Well, that changes things !

[Gunmetal blue2]

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Do the leak test then make sure you got spark from all plugs. If it does no fire in the order of the 1-2-4-3 but you have spark. The body of the top of the distributor is bad. Make sure that all spark plugs are good. You say he changed things back is he running 6 or 12 volt. Make sure the point are gap .18 to .22. Take the cap off and make sure you have a spark at each contact point. It should have a nice blue looking spark.

[George Miller]

Did he do a compression check? If not that would be the first step. It could be a broken intake valve spring or sticking intake valve. It could also be a leaking intake gasket. When you get a car like that with no history. Who knows what the guy did to that engine.

You said he tried a different dist.

[Tom Wesenberg]

Open the valve on a propane torch, but don't light it. Move it around the intake manifold to check for air leaks.
As mentioned, do a compression test first to make sure you have at least 50 pounds of compression.

[Fast31]

Thanks for all the input. Everything was fine, only the camshaft looked odd and after removal it was clear it's probably a very "hot" cam. The top of the lobes are not as pointy as the Model A's. The cam was swapped for a model B cam and the car idles and runs beautiful now with plenty of power. The cam lobes of the "hot" cam don't seem to have worn down, so it's a bit of a mistery why it was only running on 2 cylinders when idling and on low revs.

[1931 flamingo]

When you replaced the "hot" cam, how far out were the valve clearances??
Paul in CT