1956 Cylinder heads

[Edward M.]

When during the 1956 year (calendar date and / or approximate VIN #) did the change from 306 to 762 cylinder heads occur?

[Jack H.]

Re: 1956 Cylinder heads

NCRS and Noland Adams agree the '306 heads were used on early engines (210/225 HP) with short-lived, 2-bolt exhaust manifolds while most later engines (225/240 HP) used the '762 casting heads with 3-bolt manifolds.

Noland identifies the approximate change over point as being between VIN 1658 and 1663, but I wouldn't try to hang my hat on that since Noland's data is pretty well aged today. Plus, Noland actually says, "However, some late original 1956 Corvettes have been observed with the earlier '306 heads. Apparently, their use did not end when engine types were changed between 1658 and 1663."

[Bernard M.]

Re: 1956 Cylinder heads

It's my opinion that the 306 heads continued to be used in Corvette single 4bbl applications after the switch to 762s was made for 2x4s. I don't have my judging guide at hand, but I believe it substantiates that. The 306 heads were used throughout the passenger car line for 1x4 cars.