1966 BB Distributor question....

[Larry S.]

I am wondering if on my (427-425HP) distributor, the dimple on the bottom gear should be on the same side as the rotor contact?? Seems I read that somewhere. Currently, it is not, and turning the bottom gear around 180 deg. will change the setting by 1/2 a tooth. Will that advance or retard initial timming?
Finally, should all GM V8 distributors line up the rotor and the dimple? Thanks in advance.

[Duke W.]

Re: 1966 BB Distributor question....

Drive gear indexing does not change the timing per se, but it changes the orientation of the distributor housing at a given initial timing by about 14 degrees.

This can cause the VAC to interfere with something solid before the initial timing can be achieved.

On C1-C2 SBs if the dimple is 180 degrees away from the rotor tip the VAC will hit either the manifold or coil bracket before the correct initial timing can be achieved, so the gear must be installed with the dimple pointing the same direction at the tip.

A "backwards" gear is easy to recognize on a SB because the VAC will be at the limit of travel -against the manifold or coil braket rather than about half way in between.

AFAIK all Corvette distributors including BBs should have the dimple facing the same direction as the rotor tip.

Duke

[John H.]

Re: 1966 BB Distributor question....

If you have an aftermarket cam, all bets are off - the aftermarket cam manufacturers (and the aftermarket distributor drive gear manufacturers like MSD) don't recognize the GM indexing specs for the drive gear on the cam relative to the dowel pin or for the driven gear on the distributor relative to the shaft (and rotor).

[Larry S.]

Re: 1966 BB Distributor question....

Thanks Duke and John,
No, everything is original (cam, distributor, etc) and I found that the dimple is backwards making it hard to get much timing adjustment.
My 64 Fuellie is the next to check as it has little adjustment on it either.
Thanks again for the wealth of knowledge.