1972 bell housing # ?

[Calvin C.]

Is the correct bell housing for a 1972 350 four speed car #403.

thanks
cal

[John H.]

Re: 1972 bell housing # ?

Yes (unless it's an LT-1).

[Calvin C.]

Re: 1972 bell housing # ?

Thank you
cal

[Joe L.]

Re: 1972 bell housing # ?

John-----

You've got to take off that Camaro hat! That thing is messing with the "Corvette side of your 'noggin'". All 1972 Corvettes with 4 speed used a 14" flywheel with the GM #3899621 bellhousing EXCEPT ZR-1 (LT-1 engine with special HD performance package). The ZR-1 did use the GM #3858403 bellhousing (for those 20 that were ever made).

[John H.]

Re: 1972 bell housing # ?

Joe -

Yup, must be the "hat" again, but now I'm more confused - last time I botched that answer, you corrected it, and I made a (wrong, apparently) note that doesn't agree with the Colvin book either. My messy chart shows the 403/small flywheel/clutch on all '64-'72 small-blocks (except LT-1), and the 621/big flywheel/clutch on '73-'81 small-blocks plus '70-'72 LT-1. Throw the eraser, I'll duck and pay attention, if you'll help me fix my chart

[Joe L.]

Re: 1972 bell housing # ?

John-----

Why, of course, I'll help you with the chart. Some of the information in Colvin's book regarding bellhousings is not completely accurate. In fact, the bellhousing section (which only appears in the Corvette By the Numbers book and not the others) is just about the only chapter where there are weaknesses. Nevertheless, there's a LOT of good information there and I'm very glad that he added it to the book. Anyway, here's the deal, but this applies specifically to Corvette applications; other Chevrolet cars, including Camaros, used different bellhousings in many cases:

1964-68 ALL small block-----GM #3840383 or GM #3858403 bellhousiings. These are pretty much identical bellhousings. However, the '383' usually has no bosses for clutch cross shaft on the upper sides of the bellhousing; the '403' has them on one side or both sides (I've seen both configurations). Sometimes, neither is drilled and tapped, sometimes one is drilled and tapped, sometimes both are drilled and tapped. This provision is superfluous for Corvette applications since the boss/tapping is not used for ANY Corvette application. The '383' is mostly seen in earlier C2s with small block (64-E66). After that, the '403' is used mostly, if not exclusively. All applications used 12-3/4" flywheel;

1965 L-78----Usually GM #3858403; some might have used the 3840383. Both would be equally functional for a Corvette. All used 12-3/4" flywheel;

1966-E1967 Mark IV (except L-88)-----GM #3872444. This bellhousing is used with a 14" flywheel. All 1966-67 Corvettes with Mark IV (except L-88)used a 14" flywheel;

L1967-74 Mark IV (except L-88/ZL-1)-----GM #3899621. This bellhousing is used with a 14" flywheel. It is identical to the 3872444 EXCEPT that one of the reinforcing ribs on the upper, left side is configured differently (probably for clearance purposes for some chassis application besides Corvette);

1967-69 L-88/ZL-1-----GM #3858403. Used with 12-3/4" flywheel;

1970-72 ZR-1-----GM #3858403. Used with 12-3/4" flywheel. It is possible that some very early 1970 LT-1 without the ZR-1 package also used this set-up. I've never been able to confirm it, though;

1969-1981 ALL 350 (except ZR-1 and, possibly, 1978 L-48 with 4 speed)-----GM #3899621. This bellhousing was used with a 14" flywheel. Some GM PART #3899621 bellhousings used during approximately the 1978-81 period carried casting #464697. Most 3899621 bellhousings carry the 3899621 casting number, though.

1978 L-48 with 4 speed----MAY have used bellhousing GM #3858403. I've never been able to confirm this. I wish some folks with original 1978 L-48s with 4 speed would "report in". This bellhousing would have been used with a 12-3/4" flywheel. 1978 Corvettes with L-48 and 4 speed DID use a 10-1/2" clutch. However, it's possible that this clutch was used with a "dual-drilled" 14" flywheel. In that case, the GM #3899621 bellhousing would have been used.

1982 -----no bellhousings used; all 1982 Corvettes were THM-700

[John H.]

Re: 1972 bell housing # ?

Thanks, Joe - much appreciated! My messy old chart is history, now that you've provided "the right stuff"

[Joe L.]

Re: 1972 bell housing # ?

John-----

I'm real confident about the accuracy of the information, too. The "question marks" are early 1970 LT-1 (non-ZR-1) and the 78 L-48 with 4 speed. If I could get the answers to those, I'd have the whole 64-81 period covered.

It's real important to keep in mind, though, that my information only applies to Corvettes. The bellhousings/flywheels used for other Chevrolet applications over the same period are, in some cases, different. So, when you're wearing your Camaro hat, forget all about this information.