Are 3A & 4A Distributors Interchangeable?

[The Professor]

Found myself a replacement 3A distributor yesterday in the junkyard with about 177k miles on it. Doesn't feel like any shaft play and the mechanical advance does move. On my way out I walked past a Corolla with a 4A and only 109k miles on it.

I was curious if there was anything about the 4A distributor that would prevent me from using the lower mileage unit on my 3A-C.

[Petros]

I think they are the same distributor, or similar enough where it will swap out no problem. you may have to swap out the connector, or it may have a slightly different advance curve, but that should be better anyway.

there was a form member that was using a 4ac distributor in his Tercel, I do not recall who, it was a long time ago I read the post.

[The Professor]

They look identical, though the last set of numbers on the little I.D. tag are slightly different. May have to go back and nab the low mileage unit...