clutch kit

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Sep 28, 2018 | 11:56 AM

mustang81

Thread Starter

Laughing Gas

Joined: Jan 2006

Posts: 883

Likes: 7

From: New-brunswick,Canada

clutch kit

i order a clutch on ebay but it dont fit. He said it will fit 6.6 and 7.5??? I ask the ebay buyer to send it back but he want my vin #. it was a 351m 1979 f-250 4x4 with a c6 auto original so its useless to send him that vin #. I switch to 400 crank and tim piston and match a 4 speed manual. Did someone here have a 1979 400 4x4 with a 4 speed np435 that i can use the vin # so i can order the good clutch ? thanks,Serge.

Sep 28, 2018 | 04:11 PM

mark a.

Lead Driver

Joined: Mar 2004

Posts: 8,924

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If you are using a 351M flywheel you need a 11 1/2" clutch. The 400 used a 12" clutch. You can use either flywheel on either engine.

Sep 29, 2018 | 10:48 AM

mustang81

Thread Starter

Laughing Gas

Joined: Jan 2006

Posts: 883

Likes: 7

From: New-brunswick,Canada

so i must have the 400 clutch and the 351m flywheel. the clutch is to big
i buy a 4 speed with the flywheel and pedal clutch and linkage. i should check that if it was a 351m flywheel from the guy i bought it from. I didnt know he have 2 flywheel one for the 351m and one for the 400 if i understand good ?

Sep 29, 2018 | 11:53 AM

mark a.

Lead Driver

Joined: Mar 2004

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Yea, I never understood why the 351M needed a smaller flywheel either, strange as it is.

Oct 1, 2018 | 07:12 PM

mustang81

Thread Starter

Laughing Gas

Joined: Jan 2006

Posts: 883

Likes: 7

From: New-brunswick,Canada

is it ok to run a 351m clutch on a 400 ?

Oct 2, 2018 | 10:39 AM

dogdays

More Turbo

Joined: Sep 2003

Posts: 516

Likes: 27

I can't believe it. So much misinformation in such a small time.

There is no such thing as a "351M clutch." There is an 11" Long style clutch used in Ford 351Ms..

The 351M and 400 use the same flywheel casting. The 351M is drilled for an 11" pressure plate. Not 11 1/2" The 400 is drilled for a 12" clutch pressure plate.
It is a minor task to have a machine shop drill and thread new holes to allow the 351M flywheel to accept a 12" pressure plate. It cost me $35.

Ford engineers put in the clutch the engine demanded. I'm sure there were design standards. Clutches have torque ratings and the 400 has more than the 351M.

HOWEVER, there have been probably millions of 11" clutches behind big blocks. It's not a big deal. Just a regular 11" clutch should have no problem with a normally aspirated 400.

Why doesn't everyone use the largest clutch they can? An increase in diameter nearly always increases the spinning momentum of the clutch disk and it is that momentum that the synchronizers have to burn off when you shift.

R.