Mopar Action On-line – Tech Questions

Tech Question

Roy Sommer, Hamilton, Ontario

Hello Richard:

I have an nos Accel dual point small block Mopar distributor that I just picked up at a recent swap meet for very little coin. Problem is I want to use it on a 440 block. I’m a good welder and I intend to remove and lengthen the distributor shaft to RB block size. I know factory dual point units had contact points facing in different directions for small and big blocks since they rotated in opposite directions. As an engineer can you tell me if there is a difference or any problem that may occur if the contact points are not facing in a certain direction when they are opened? If they must be facing a certain way then this project won’t go ahead. Keep that great Mopar tech coming!


Think about it! In a smallblock, as the RPM increases, the cam (or reluctor, in electronic distributors) is rotated CCW, opposite distributor rotation, as the RPM increases, advancing the timing. Put that unit in a big block (CCW distributor rotation), and you’ll have a very nicely operating mechanical RETARD system. Duh!

Ditto the vacuum advance, which, incidentally, is an absolute MUST in any car which sees even a small amount of street use.

Basically, the guts of SB distributors are mirror images of big block dizzys.

The only exception to the above would be for a welded-fixed-timing (no advance) unit for a drag-only car. I think the point rubbing block vs. cam deal would work fine in the opposite direction — the cam is symmetrical. That setup, though, is very tough on starters and ring gears!



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