Quick bell housing question

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May 4, 2016 | 07:18 PM

jimkari

Thread Starter

Racer

Joined: Apr 2005

Posts: 484

Likes: 5

From: Madison Wisconsin

Quick bell housing question

I am considering switching my '73 L-48 from an auto to a manual trans. I've been doing some research, but I am a little confused on the clutch / bell housing size. It seems like 11" was the standard size in '73, but when I spoke with a Corvette salvage guy that's been in the business for 40 years, he said the 11" is hard to find and the 10.5" is much more common. Based on what I researched, it appears GM went to the 11" clutch around 1970. Can anyone set me straight on what is the right clutch / bell housing I should use?

Thanks,

Jim

May 4, 2016 | 08:09 PM

jnb5101

Le Mans Master

Joined: Jul 2006

Posts: 8,117

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From: charlotte north carolina

The larger 11" bell housings are more expensive, but either a 10.5" or a 11" clutch and flywheel can be used with them. For your application (unless you plan serious mods to the engine) a 10.5" clutch will meet your needs. When you order the flywheel, make sure you order the correct style(one or two piece rear seal). Also, a stock type clutch is your best bet. Some of the after market clutches have throw-out geometry problems.

May 4, 2016 | 08:11 PM

righthanddrive

Pro

Joined: Dec 2015

Posts: 578

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From: colo

You can use either one, but you may need to change your starter if you have the larger flexplate ( I believe it is 163 tooth )

You also have to know the teeth on the input shaft of the transmission for the correct clutch plate.

The 10.5 " bellhousing will not fit over the 11" clutch set-up.

There are lots of 11" bellhousings to be found, but there are 2 different size holes for the transmission faceplate shaft, although there are adapters available to reduce the size of the hole.

You also have the clutch pedal, 'Z' bar, neutral safety switch among other parts to add into the mix to switch over,not to mention the hole for the shifter.

Good Luck,

Ed

May 4, 2016 | 08:14 PM

cagotzmann

Melting Slicks

Joined: Jun 2011

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Quote:

Originally Posted by jimkari

I would remove the transmission inspection plate and count the number of teeth on the flex plate. It will be either ~ 168 or ~ 153 teeth.
This will then determine which is the next step. Your flywheel would need to match the count ( or change your starter as well ).

The bell housing choice depends on the transmission you will be using.

4,5, or 6 speed. ?

Last edited by cagotzmann; May 4, 2016 at 08:16 PM.

May 4, 2016 | 08:17 PM

rgwoehr

Burning Brakes

Joined: Aug 2015

Posts: 876

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From: Columbus, IN

I'm pretty sure 11" is the correct one to use. Original GM 10.5" bell housings are easier to find than the 11" ones but it's not impossible to find them. Be careful if you're buying one on eBay because there are a bunch that are just listed as 11" bell housings, but they are truck bell housings which have a larger hole for the bearing retainer and won't work with a passenger car tranny without an adapter. You can tell them apart by looking at the bottom. Truck ones have a "bump" that the car ones don't. You can see it in photos here: http://www.4speedconversions.com/486.html

May 4, 2016 | 09:07 PM

jimkari

Thread Starter

Racer

Joined: Apr 2005

Posts: 484

Likes: 5

From: Madison Wisconsin

Thanks guys, very helpful information. I really appreciate the quick response. I'd like to avoid changing the starter if I can because I just purchased that when I was doing my body off restoration.

Jim

May 5, 2016 | 08:01 PM

larrywalk

Melting Slicks

Joined: Oct 2002

Posts: 2,317

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From: St Louis MO

Quote:

Originally Posted by cagotzmann

No need to count teeth! If the starter has staggered mounting bolts, you have the larger flywheel/flexplate with 168 teeth. If it has an inline bolt pattern, it uses a 153 tooth flywheel/flexplate.