62--74 Corvette Distributor Mainshafts

[Christopher R.]

Are all the 62-74 Corvette distributor mainshafts the same? 62-74 Corvette distributors are the tach drive distributors. I thought they were all the same, until I saw 2 different ones listed in a vendor catalog. The catalog didn't make the distinction clear to me. So I looked in a 1973 edition of the Chevy parts catalog, and found that Chevy had many different mainshafts. What're the differences among them? I'm trying to figure out what one I need to buy.

[Terry M.]

Re: 62--74 Corvette Distributor Mainshafts

Chris the differences in the distributor main shafts relate to the shape of the auto cam at the top of the shaft. This cam effects the characteristics of the centrifugal advance curve -- along with the springs and weights, of course.

[Mike E.]

Re: 62--74 Corvette Distributor Mainshafts

62, for example, has both centrifugal advance and vacuum advance--those would be different profiles.

[Wayne M.]

Compare mainshaft autocam shapes ....

.... as others mentioned. One on left (stamped and underlined "54") is from a (probable) service 1111157 TI distributor ('66 and '67 L79 w/K66).

On the right, stamped "247" we have the shaft from a 1111267 K66 tach drive distributor for '67-69 Camaro Z28's (over-the-counter ?).

But the shaft itself is different for Fuel Injected cars (gear to drive fuel pump and tach), and on the 1111263 ball bearing (no vac adv.) K66 racing distrib.

[John H.]

Re: 62--74 Corvette Distributor Mainshafts

Chris -

There were MANY different Corvette tach drive mainshafts, depending on the autocam characteristics, but only one or two are still around (or reproduced); doesn't matter much which of the two you buy - anyone with a Sun machine and an assortment of weights and springs can set up whatever advance curve you like.