Why Choice of 396 Displacement?

[Everett Ogilvie]

When the first big block was put into the Corvette mid-'65, why was the displacement 396 cubic inches? It was based on the Mark II racing 427 - anyone know what prompted 6 months of production of a unique engine, which then went to 427? Just thought I would ask for some historical perspective.

[Edward McComas]

Re: Why Choice of 396 Displacement?

I seem to recall reading that when the big block first came out (1965), there was a GM policy (or perhaps a Chevrolet policy) that limited engine size to no more than 400 cubic inches. That policy was recinded / deleted the following year.

[William C.]

Re: Why Choice of 396 Displacement?

GM policy for "A" body, GTO, Chevelle SS, 442, etc kept it at 400 inches or less, until recinded in '70. Full Size Pass cars were ok so 427 was used in '66-up. I believe Corvette got a "Sports Car" exemption.

[Verne Frantz]

Re: Why Choice of 396 Displacement?

Actually a 427 was used in '63 in full sized cars. Very limited numbers; the RPO Z-11 option, based on the "W" block. And the full sized cars were treated to a 409cid as of mid '61 production.
I believe Zora tested a 409 for '63 Vette production, but no one can find any engineering data to support that.
Verne.