C & M block differences

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Jul 21, 2003 | 02:13 PM

#16

CJJTulsa

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C & M block differences

The 351C was made from 70-74, and the auto was available all 4 model years. The cranks won't interchange, but I'm not sure if the flexplates will or not. Seems like the 400 (same as the 351M) with the small bellhousing pattern used the same flexplate with the FMX tranny as the Cleveland, but I don't know for sure. If so, then the flexplates should interchange.

Jul 21, 2003 | 10:49 PM

#17

Brian460

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From: Paola, KS

C & M block differences

The 351M-400 is a 429/460 bellhousing and IS different then a 351C which is the same as the small blocks (289, 302, 351W, I-6)

I believe but not positive on this that the flywheel from a 351W will work.

Jul 22, 2003 | 06:13 AM

#18

CJJTulsa

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C & M block differences

Most 400s are the 429/460 style, I was referring to the "FMX" block that used the small style (C4/FMX) bellhousing pattern. I think it would use the same flexplate as the Cleveland, that's why I figured the "M" block flexplate would be the same. Unless the 351M is balanced different than the 400. I have that flexplate, but never saw where Ford put a number on it.

Jul 22, 2003 | 11:35 AM

#19

johnsalterego

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From: Dallas/Fort Worth

C & M block differences

flexplates are balanced and counter weighted like harmonic balancers; I can't find anything that states the balancers will interchange between 351w's and Clevelands, so I doubt the flexplates will either, but I wouldn't swear by it. the number of teeth on the ring gear will be wrong for the 351M/351C swap - even if it would physically fit I doubt the starter would work right. Since the cranks are different weights vibration would also likely be a problem...

Jul 22, 2003 | 12:02 PM

#20

CJJTulsa

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C & M block differences

I would suspect you're right; but there is a post by Brian S. (who looks to know his stuff) on another board about using a 400 balancer on a 351C. If that would work, seems like the flexplates would also interchange, unless the 351M is different than the 400. The crank is, but the 400 crank is entirely different than the Cleveland. We need a good interchange manual.......

Jul 22, 2003 | 12:19 PM

#21

GT40man

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From: Jax FL

C & M block differences

they still balence the same weight

Jul 22, 2003 | 12:46 PM

#22

bubbaf250

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From: (near) Denver USA

C & M block differences

The imbalance weight is the same for all 335-series engines (351C, 351M, 400) at 28 oz.

Ford calls their front-end part a "harmonic balancer" because it provides both external balance and harmonic damping.

Even though all 335-series engines have the same imbalance weight, the crankshaft harmonic frequencies are determined by the design of the crankshaft, which is unique for each engine type. That's why Ford used a different harmonic balancer part for all three engines, with the same imbalance weight.

Ford always used a single flexplate part for both M-block (351M/400) engines, and although the flywheels were different originally (same casting with different clutch plate mounting), Ford now offers a single flywheel service part for both engines (drilled with both sets of mounting holes).

The 400 with the "small-block-style" bell housing would have to use the 351C flexplate, as the standard 400 flexplate wouldn't fit inside the smaller bell housing.

Jul 24, 2003 | 09:45 PM

#23

78ford100

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From: Western IL

C & M block differences

I took the flexplate off the Cleveland today and compared it to a 302 flexplate I had on the wall. They look identical, same diameter,same bolt patterns, same 28oz weight. Would a 302 flywheel with the 28oz weight fit?

Oh, by the way, does anyone know if a 4bbl stock manifold will fit the stock 2bbl heads?