1966 427 390 bellhousing

[Tony C.]

Hi
I have 1966 427 390 with a build date of 4/1966 with a bell housing that has a casting number 3899621 The judging guide said it should be # 3872444 Noland Adams Books says some 1966 427 390 where found to have casting number 3899621 what do you think is correct. If 3899621 is incorrect what is it for.
Thanks Tony

[Joe L.]

Re: 1966 427 390 bellhousing

Tony-----

I seriously doubt that the 3899621 was used for a Corvette originally built at the time yours was. The GM #3872444 was used for 1966 Corvettes with 427. In fact, the 3872444 has also been found on very early 1967's, too, although most 67's with big block (except L-88) used the GM #3899621. The GM #3899621 continued to be used for all Corvette big block applications except L-88/ZL-1 through the 1974 model year. The 3899621 was also used for all 1969-81 Corvette small blocks except 1970-72 ZR-1. It was used for many other Chevrolet applications with 14" flywheels.

Notwithstanding the above, I would not completely rule out that the 3899621 was originally used on your car. Functionally, there's no reason that it could not have been. And, it may be that for some period, say the later 1966 through early 1967 period, the 3872444 and 3899621 were being used randomly for Corvette big blocks. The 3872444 and 3899621 are absolutely functionally equivalent for a Corvette application. The only difference between the 2 bellhosuings is the configuration of one of the reinforcing ribs seen at about the 11:00 o'clock position-----on the 3872444 the rib is narrow and peaked (like all the other ribs); on the 3899621 the rib is wide and flat. I believe that this change was made for clearance on some other, new for 1967 Chevrolet application, possibly Camaro.

One thing to keep in mind: the 3872444 was discontinued from SERVICE and replaced by the 3899621 in November, 1966. So, if any application originally using a GM #3872444 needed to have the bellhousing replaced after that time, the replacement obtainable through GM dealers would be the 3899621.

[Tony C.]

Joe thanks for the help *NM*