I have found a 1979 Bronco I want to buy it has a 351C in the truck and a C6 Trans. I have owned a couple different vechicles from this time period, I want to know how to tell the difference between a 351C, 351M and 351W. By looking at it, I can't go pulling the truck apart before I buy it. Let me know as soon as ya think of something.

 

The quickest way of differentiating between the different familys of Ford engines is to simply count the valve cover bolts.
2 bolts: 239/256/272/292/312 (produced from 1954 to 1964)
5 bolts: 332/352/360/361/390/391/406/410/427/428 (FE engine)
6 bolts: 221/260/289/302/351W
7 bolts: 429/460
8 bolts: 351C/351M/400
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The early 351W has four extra intake manifold bolts (13, 14, 15 and 16). If you see them, it's definitely a 351W.

Windsor engine characteristics

Thermostat housing bolted to the front of the intake manifold

All 289/302/351's have intake bolts 90 degrees to the ground

289/302/351's have evenly spaced exhausts aimed 90 degrees from length of head

5/8" (18mm) spark plugs

The 351W and 302 are very different:

The 351W has a taller deck height than the 302. (a 302 will have the intake almost flush with the base of the distributor... where it goes into the block..... a 351w will have about 1/2 inch lip there where the intake meets the block.)

Since the deck height is taller the intake manifold is wider on the 351w than on the 302.

The 351W uses a larger main journal than the 302. there are 2 physical ways of telling a 302 vs. a 351w. Also, in between the frost plugs on a 351W there will be what appears to be a triangle or diamond (the way I was told) indented cast into the block...a 302 doesn't have those.

a 351W is wider between the heads compared to a 302 (the intake manifold is wider by about 1-1/2") and 351 pistons have a different pin height. You can use 302 pistons in a 351 if you stroke it to a 393

quick ID tip: The lower thermostat housing bolt on the 302 will be below the top of the water pump and you won't be able to put a socket on it. On the 351W you can remove the bolt with a socket.

Cleveland engine characteristics

The thermostat housing is on the block extension which contains the timing chain

deck height makes a 351c intake not fit on a 400, Spacer plates are available to use a 351C intake on a 351M/400, but it's more practical to use these mainly for large port intakes on 400s using 351C 4V heads.

351C manifolds are dry, no water passages or thermostat housing....thermostat housing goes into the front of the block.

spark plugs will be the smaller 14mm type

The Cleveland (351C) has the small 300/302/351W bell housing pattern.

The 302C is a de-stroked Cleveland, the block is identical to a 351C, but the crank rods and pistons are all engine specific. The 302C heads are the small combustion chamber, small runner heads.

M-series engine characteristics

The 351M/400 was only available with small ports, same as 351C 2V. An Edelbrock Performer for these are wider and should say Performer 400 on the top.

351M/400 manifolds are dry, no water passages or thermostat housing.

There is about a 1" rib cast onto the block on the taller 351M/400 which runs along side the distributor going from the front of the block extension back to the intake manifold.


This is a very rare Ford 400 block, one of a very few cast to fit the standard Cleveland bellhousing. These blocks have blank engine mount bosses which can be drilled to suit standard Cleveland engine mounts making them a direct replacement for a 351C (assuming no height/width problems).

All engines in the M series (family) have the vertical bolt pattern on the fuel pump. That includes 351C, 351M, and 400.

M-block engines have the taller intake manifold front mating surface (almost an inch above the distributor mounting hole and front cover housing) and is quite apparent

The only real differences between a 351M and a 400 are the crank and the pistons.

351M and 400 heads are identical, are also nearly identical to 2V Cleveland heads

The 351M and almost all 400's have the large bell housing pattern like the 429/460.

The only 100% positive way to tell if you have a 351M or 400 is to drop the oil pan and check the casting numbers on the crank. They should be on the side of the first counterweight. A 400 crank will have 5M, 5MA or 5MAB casting code. A 351M crank will have a 1K casting code.

400 with 302 bellhousing was made in '73, and will also have the regular 400 bellhousing mount casting. Top 2 bellhousing bolt holes are 5 inches apart on a 302, 7 3/4 inches on 400.

 

Not that I can possibly add much further detail to JBronco's information there but I can say that IF you have found a 79 with a 351C in it then you found a 79 that has had the engine swapped. The 351M and 400 were the only two mills offered in the 78-79's.

 

It's been a long time since I played with the Cleveland stuff, but didn't they have a 2 or 4(designating 2 or 4 barrel heads) cast into the top corner of the heads next to the valvecover? I don't believe this was done on the 351 modified? Also, 351 M use the 429/460 bolt pattern for transmissions where the 351 C uses 302 bolt pattern.

302:


460:

 

351C = 1970/74 Ford/Merc Passenger Cars only.

351C/351M/400 do not have a 'typical' timing cover, just a flat plate.

The fuel pump bolts to the left (drivers) side of the block. The bolt pattern is at 6 & 12 o'clock, the only fuel pumps to have this pattern.

 

Correct, but he trying to differenciate between a."m" & a "c" if I read this correctly?

 

All the Cleveland heads I've seen had the 2 or 4 on the corner, no M heads with numbers cast on them.Valve covers are the same so some people either don't know the difference or just trying to pass an M block off as Cleveland to make you think it's something it's not.