1966 427/390 Roadster

[John Hocking]

I am getting mixed messages on the right numbers for the 1966 427/390hp exhaust manifold. The car in question has #'s 3880828...but the book I am using says they should be 3884504/3892307 for the left and right. The car is a 1966 427/390hp 4 speed. Please help?!?!?!?!?!

[Mark L.]

66 Exhaust Manifolds

The right side is 3880828 and the left is 3880827. The part numbers stay the same through 1969. Your car should not have the smog holes unless it was sold originally in CA. I would suggest you obtain the 66 Judging Guide as it is a wealth of info on part numbers, finishes and configurations.

[Joe L.]

Re: 1966 427/390 Roadster

John----

The book that you're using is incorrect. The GM casting #3884504 and 3892307 manifolds were used on 1966-67 passeneger cars with hydraulic lifter big blocks. These manifolds are of a configuration NEVER used on Corvettes.

Incidentally, 1966 passenger cars with L-72 used the same 3880827 and 3880828 manifolds as Corvette. The Corvette manifolds will fit on most 65-69 passenger cars with big block, although they were not so-used except for the 1966 L-72 (and, 1965 L-78 passenger cars which used the same 3856301/3856302 manifolds as Corvette). The Corvette manifolds will not fit Chevelles, Camaros, or Chevy IIs and, basically, that is why the "log" type manifolds were developed. However, the "log" type manifolds used on passnger cars were generally different than those used on Chevelles, Camaros, and Chevy IIs. The passeneger car "log" manifolds were more of a "hybrid"---sort of "between" the Corvette and Chevelle/Camaro/Chevy II manifolds as far as runner configuration goes.

This brings up an interesting side note. Why was the 3856301/3856302 manifolds used only for the 1965 model year? After all, the Corvette big block manifold requirements did not change after 1965 as far as fitment goes. Plus, the 3880827 and 3880828 are nearly identical to the 3856301 and 3856302, respectively. So, why the change? Well, there is one significant and functional difference between the 2 sets of manifolds. The later have provisions for a boss of A.I.R. fittings; the 1965 manifolds do not. Beginning with the 1966 model year, exhaust emission controls began to come into play, first in California. So, for 1966, the manifolds were redesigned to include a boss suitable for A.I.R fittings. A few other minor changes were made, too, but the primary change was the boss addition. Not all 3880827 and 3880828 manifolds are drilled and tapped for fittings, of course. GM #3880827 and 3880828 was BOTH the casting number and part number for the manifolds not equipped for A.I.R. GM #3880833 and 3880834 were the PART numbers for the 3880827 and 3880828 casting manifolds equipped for A.I.R.

[Wayne M.]

There's also the air heat tube on the RH 302

which was eliminated on the 828 in 1966 (but the boss remains). But I agree, were those minor changes that called for only a part # change while retaining the casting #.