[BigMike]

I have 2 bellhousings to choose from when I convert my '71 Nova 6cyl Powerglide to a 4-speed:

I have one on the shelf, a "621" with flywheel and clutch in good shape.

I also have a '74 parts car with a 6cyl 3-speed. I understand the 6cyl bellhousing, flywheel and clutch will work behind a V8. Is this so?

However:

Recent postings warn a that truck bellhousing has a too large center hole for a Muncie or Saginaw. Is there a "Truck 621"? What is the diameter of the truck center hole? The car center hole? I can't find the answer with the search function. I see that the truck center hole is 3/8" larger but I don't know the correct diameter of either.

The engine is a mild 305 that will eventually be replaced with a 327. Someday.


Thanks.

 

[JTW]

Mike,

The register bore for the 621 bellhousing should be 4.68", which would allow it to mate up with a Saginaw or Muncie 4 speed. I have a 621 loose in my garage at the moment and it's register bore measured 4.68". I'm not aware of a 'truck' 621 with a larger register bore, but if yours measures 4.68" you should be fine.

The bellhousing behind the 6-cyl. in your '74 parts car should be the smaller Chevy bellhousing which would limit you to a 10.5" clutch. The 621 is the larger bellhousing which can accomodate a 168T flywheel and an 11" clutch.

You could probably use either one, but if you are planning to build a strong V8 you may want to use an 11" clutch with the 621 bellousing.

 

[BigMike]

Thanks JTW, that was what I was looking for. I never heard of a "truck 621" either but then I'm no expert.

Now I need to determine if the flywheel and clutch that came with the 621 bellhousing is 11" stuff. I got it with a 283 I bought a few yrs. ago.

As I need to buy new clutch stuff and I starter I guess I have my choice of 10.5" or 11" depending on which bellhousing I pick.

I've been a member here quite a while but don't post much as nearly everything I need to know I find with the search function.

Thanks again.

 

[nova656567]

I agree with JTW on most of the info, but question the part regarding fitting a 168 tooth flywheel with the 71 bellhousing. I think you can fit 168 tooth with the stock bellhousings from 68 & up. Let me know if I'm wrong on this.