Bell housing cover plate

[Kurt G.]

Over the last couple of months I've been restoring the front end of my '72 350/4 speed and ran into a bit of a problem yesterday when I got the car back on its wheels and started it up for the first time in awhile. I have a strange clicking noise that is rpm sensitive. The only parts that came of the engine that are close to any moving parts are the lower bell housing dust cover and the starter. When re-installing the dust cover I wasn't sure if the upper edge of the cover fit under or over the upper section. Which is correct?

[Joe L.]

Re: Bell housing cover plate

When re-installing the dust cover I wasn't sure if the upper edge of the cover fit under or over the upper section. Which is correct?

Kurt-----

I don't really understand what you're describing here. However, the upper edge of the cover (slightly offset section) should fit tightly against the block.

Here's another tip: if your cover is original to the car, it will likely not have raised "tangs" on either side of the semi-circular central "cutout". These tangs are designed to clip behind the rear semi-circular lip of the oil pan. If you don't have them I strongly recommend obtaining a current example of the cover, GM #3843943. This is the original part number but the cover was changed somewhere along the way to include the "tangs". These "tangs", when installed as designed and as I have described, will absolutely prevent contact of the crankshaft with the cover. Yes, this cover is probably not "correct" for your year model. In this case, I say to hell with correctness. The minor deviation to correctness is far less important than the functionality imparted by the revised cover. Of course, if the car is a "trailer queen" the original cover will work just fine.

[David L.]

Re: Bell housing cover plate

Enclosed are photos of an original 3788422 cover in red (replaced by GM # 354497 in Jan. 1976) as well as a NOS 3843943 cover with the raised "tangs" as mentioned by Joe. The original black paint on the NOS cover is not the best quality as the edges of the cover have surface rust even though it has been stored up in my dry garage attic for the last 28 years.
I do not have a 354497 cover.

Joe,
It's interesting that the 3788422 cover is listed for the 1970 Camaro Z28 but the 3843943 cover is listed for the 1970 Camaro SS350 and all 1970 Chevrolet models w/396,400,454 engines in my 1970 Chevrolet Parts Catalogs (Jan. 1970 & Oct. 1970).

Dave

[David L.]

Re: Bell housing cover plate

My 1972 Corvette Parts Catalog (Sept. 1971) lists cover # 3788422 for the 1972 Corvette w/4-spd. (350) and the 3843943 cover for the 1972 Corvette (350)(exc. A.T., 4 Spd.).

Dave

[Joe L.]

Re: Bell housing cover plate

Enclosed are photos of an original 3788422 cover in red (replaced by GM # 354497 in Jan. 1976) as well as a NOS 3843943 cover with the raised "tangs" as mentioned by Joe. The original black paint on the NOS cover is not the best quality as the edges of the cover have surface rust even though it has been stored up in my dry garage attic for the last 28 years.
I do not have a 354497 cover.

Joe,
It's interesting that the 3788422 cover is listed for the 1970 Camaro Z28 but the 3843943 cover is listed for the 1970 Camaro SS350 and all 1970 Chevrolet models w/396,400,454 engines in my 1970 Chevrolet Parts Catalogs (Jan. 1970 & Oct. 1970).

Dave

Dave-----


The GM #3788422 and successor GM #354497 are used for applications with bellhousings designed for 12-3/4" flywheels (e.g. GM #3840383, GM #3858403) The 354497 is very similar to the 3788422 except it has the clips ("tangs") added. I've posted photos of a 354497 in some past thread.

The GM #3843943 is designed for applications using a bellhousing designed for 14" flywheels (e.g. GM #3899621). Early versions did not have the clips ("tangs"). Later versions, as the one you pictured, did have them. Just when the change took place, I don't know. However, I think it was probably about the mid-70's. In this case, the part number did not change when the clips were added.

[David L.]

Re: Bell housing cover plate

Dave-----


The GM #3788422 and successor GM #354497 are used for applications with bellhousings designed for 12-3/4" flywheels (e.g. GM #3840383, GM #3858403) The 354497 is very similar to the 3788422 except it has the clips ("tangs") added. I've posted photos of a 354497 in some past thread.

The GM #3843943 is designed for applications using a bellhousing designed for 14" flywheels (e.g. GM #3899621). Early versions did not have the clips ("tangs"). Later versions, as the one you pictured, did have them. Just when the change took place, I don't know. However, I think it was probably about the mid-70's. In this case, the part number did not change when the clips were added.

Joe,

That makes sense.
There is an error in the 1970 Chevrolet parts catalogs. My 1970 Chevrolet Passenger Car Specifications (dated Feb. 1970) shows RPO L48, RPO Z28, and RPO L34 using an 11" clutch which would require using the 3899621 bellhousing. The 1970 Parts Catalogs lists the 3858403 bellhousing for the 1970 Z28 which can not be since it used a 11" clutch.

Dave

[Joe L.]

Re: Bell housing cover plate

Joe,

That makes sense.
There is an error in the 1970 Chevrolet parts catalogs. My 1970 Chevrolet Passenger Car Specifications (dated Feb. 1970) shows RPO L48, RPO Z28, and RPO L34 using an 11" clutch which would require using the 3899621 bellhousing. The 1970 Parts Catalogs lists the 3858403 bellhousing for the 1970 Z28 which can not be since it used a 11" clutch.

Dave

Dave-----


Yes, 1969 Z-28 used the '403' bellhousing with 12-3/4" flywheel. However, 1970 did not. Perhaps the 1970 Z-28 application was originally scheduled to use the 69 set-up but that was changed without GMSPO being notified in time.

[David L.]

Re: Bell housing cover plate

Dave-----


Yes, 1969 Z-28 used the '403' bellhousing with 12-3/4" flywheel. However, 1970 did not. Perhaps the 1970 Z-28 application was originally scheduled to use the 69 set-up but that was changed without GMSPO being notified in time.

I totally agree.