Will a 6 cyl 3 spd bellhousing fit a car 4 speed trans?

[ScottH]

May be buying a 67 c10 with a 6 cyl 3 speed manual trans soon. Would like to drop in a sbc with a saginaw car 4 speed trans. Was wondering if anyone knows if I can use the same bellhousing? Concerned that the center hole would not be the correct size.

Any info is appreciated.

Thanks

[Baddflash]

Can't say for sure if it will fit the m21 or what ever you're using but the 3spd/6cyl bell has a smaller hole than the 4spd/350 one.

[Mike C]

Yes. There are 2 different registration hole sizes on the bellhousing, the smaller car one that is also the same as the SM420 along with the truck 3 speeds, and the larger SM465 register.

You must use a 168 tooth flywheel with the truck bellhousing to my knowledge as a 153 tooth block mount starter won't clear the bellhousing mount built in.

The car transmissions bolt into the bellhousing with all 4 bolts going through the tranny and then threading into the bellhousing.

The truck trans bottom bolts screw into the transmission from inside the bellhousing at least with the iron ones I have. It could be all of mine are from 4 speed trucks but I don't think so.

You should be able to use a lock washer and nut on the inside of the bolt and make it work.

[MikeB]

The bell-housing will bolt on the the small block. Flywheel may even work, assuming you have a pre-1986 small block (2-piece main seal), but I'd replace it or have it ground. And as said above, 153T and 168T bell housings are different sizes. I kind of like the smaller one for moderate horsepower engines, because the starter location allows for more exhaust clearance, especially headers. But if this is a budget job, then run what you've got.

[ScottH]

Thanks guys, really appreciate the great info.

One followup question, not sure I am clear on the flywheel issue. I'm guessing the 6cyl 3spd setup comes with a 153T flywheel, and would have the corresponding bellhousing. Can I use this setup with a sbc / 4 speed assuming I have a starter that works with it?

[Baddflash]

I believe both engines run the same size flywheel, same number of teeth, same starter.

[MikeB]

Originally Posted by ScottH

I'm guessing the 6cyl 3spd setup comes with a 153T flywheel, and would have the corresponding bellhousing. Can I use this setup with a sbc / 4 speed assuming I have a starter that works with it?

Hard to say what size flywheel/bellhousing the 6 cyl engine used. Trucks may have used the 168. But, yes, a Muncie, Saginaw, or B-W 4 speed will bolt to either one. As mentioned in a post above, the monster SM465 will not.

Another term you will hear is "clutch diameter", which is the diamter of the clutch disc. The 153T flywheels use a 10.5" clutch disc & pressure plate, while 168T uses 11". Also, the clutch disc you'll need will be either 10-spline or 26-spline, depending on the 4-speed transmission input shaft.

So, therefore you have:

11" x 10-spline
11" x 26 spline
10.5" x 10-spline
10.5" x 26-spline

[ScottH]

Thank you!

[Mike C]

168 tooth flywheels can be any and all of the above when it comes to clutches. My Jimmy has a 12" clutch stock from '72. Most 168 tooth use 11" in cars but not sure what you get in 6 cylinder trucks as I've never messed with one!

I'm fooling around with some 153 ci 4 cylinders for jeeps right now, and they use same parts as the 6 cylinders and I just found out the bellhousing thing with a mid 50's bellhousing bolted to my engine test stand. You might be able to use a starter with an unsupported nose and run the 153 tooth flywheel but I don't have a 'Denso style starter (other than the one in my Jimmy that I don't want to take out!) to test.

Notice not starter... I'll swap to a car bellhousing once I retrieve it from the farm.