66 bellhousing

[Jeremy Hedges]

I am working on a very late 66 427/390hp, it had a 621 on it when I took it apart. I noticed in Nolans book that a late L36 also had a 621. The Judging manual states that all 427 have 444. What is going to be correct?

[Joe L.]

Re: 66 bellhousing

Jeremy-----

I wouldn't rule out that very late 1966 with 427 received a GM #3899621 bellhousing, but I very much doubt it. Early 1967 with big block (except L-88) generally used the 3872444, so that makes it doubtful that late 66 used the '621'. However, there may have been "overlap". Both bellhosuings are 100% functionally interchangeable for a Corvette, so there's no fundamental reason that either could not have been used.

One note, though: I have noted that some of the bellhousing information in Noland's survey DEFINITELY indicates a replaced bellhousing for that particular car. For example, he shows a 1965 L-79 with the 3899621 bellhousing. I can guarantee you that bellhousing was never originally installed on ANY 1965 and certainly not a 1965 L-79. Period. However, Noland does not represent that everything shown in his survey is representative of an original car---it's just what he found on the particular car.

Bellhousings are a fairly often-changed piece.

[Kent D.]

Re: 66 bellhousing

My july '66 427/390 has a 444 bellhousing on it.

[Philip C.]

Re: 66 bellhousing

my april 66 425 orig motor bought 1990 my nov 1st 427 400 orig motor I bought in 1980 and my april 67 435 orig motor clutch trans rear carbs etc have 621 bells, Ive not seen a 444 in an orig car yet and Ive seen many, could it happen I guess my 10 cent Phil 8063

[Clete M.]

Re: 66 bellhousing

In 1972 I bought an original 390 hp A/c, built Feb 1966. Had a 444 bellhousing on it.

[Joe L.]

Re: 66 bellhousing

phil-----

I would expect the 3899621 bellhousing on the 67's. Most, if not all, 1967's did use the 3899621. The '621' on the April 1966 L-72 surpises me. However, it's late enough in the model year that a "phase-in" of the '621' may have begun.

[Joe L.]

Addendum

One other thing I should have mentioned: the GM #3872444 bellhousing was only available in SERVICE for a VERY limited period of time. It was released for SERVICE in November, 1965 and discontinued from SERVICE in November, 1966. At that time, it was replaced for SERVICE by the GM #3899621. So, if for any reason any 1966 had required a bellhousing replacement after November, 1966, the GM dealer would have sold them the 3899621.

In the old days, of course, a lot of Corvettes were fitted with scattershield-type bellhousings for certain racing requirements. If the original bellhousing was lost (like in a former owner's garage) and a return to stock configuration were desired, the 3899621 bellhousing would be the one obtained at one's Chevrolet dealer.

The 3899621 bellhousing is VERY common since it was used for so many years on so many applications. The 3872444 is quite rare; next to the 60-only GM casting #3764691, it's probably the rarest of all Corvette bellhousings. It was used only for the 1966 model year in Corvettes, Chevelles and a few other applications with 14" flywheels.

GM says that the 3872444 was used for all 1966 Corvettes with 427. However, I would not preclude, at all, that late 1966's might have received the 3899621. As I mentioned previously, the '444' and '621' are 100% functionally equivalent in a Corvette and, if available, could very easily have been used in a 1966.

The 3899621 differs from the 3872444 only with respect to the configuration of one of the reinforcing ribs at about the 10 o'clock position as viewed from the rear. On the 3872444 the rib is narrow and peaked (like the other ribs). One the '621' the rib is wide and flat. Presumably, this was done to provide clearance for some 1967 chassis application that used the 14" flywheel. My guess would be that application was the 1967 Camaro SS 350 and SS 396, but I don't know that, for sure. The rib configuration difference is completely irrelevent in the Corvette application.

[Tom P.]

Re: Addendum

If this works, here is a comparrison of the aforementioned 444/621 ribs. The 621 is on top.