351M 400 flywheel question
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351M 400 flywheel question
Ok, I'm converting my truck to a standard transmission from a C6, how can I tell if my engine is a 351m or 400? What would happen if I used a 351m flywheel on a 400, or if I used a 400 flywheel on a 351m? Will I have to change the starter if I change the truck to a manual transmission?
Posting Guru
Joined: Feb 2009
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351m and 400 are the same engine, just stroked different. Flywheel is the same. I'm not certain on the starter, but I think it's the same for two or four wheel drive. A good parts house could look it up, or Mike or NumberDummy will probably be along shortly with part numbers...
Postmaster
Joined: Mar 2011
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From: Taxachusetts
351M = 3.50" stroke, 400 = 4.00" stroke, different pistons, too.
351M/400 Flywheels are the same diameter, 180 tooth ring gear for the standard trans,
164 T for the auto. So, yes - you will need a new starter also.
You also need a new harmonic balancer - depending on which (351 - 400) crank you install/have. The 351 balancer is not only 6* retarded from the 400 but weighs in a few pounds less (thinner outer ring). The (400 cu.in.) automatic HB is a hoss of a different color, too.
Ford Parts Specialist
Joined: Nov 2006
Posts: 88,826
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From: Simi Valley, CA
351M uses an 11" clutch, 400 uses a 12" clutch. Flywheels can be substituted...as long as the correct clutch size is used.
Same 351M/400 starter: A/T & M/T ~ 2WD/4WD makes no difference.
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