Identifying 351 M or W?
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From: New Orleans
Identifying 351 M or W?
I have an 82 F250. I can not guarantee the engine is the original engine or not. I do know it is a 351. How can I identify a 351W from the M if there are no labels or tags?
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Windsor valve covers have 6 bolts, M blocks have 8. However, M blocks and Clevelands have the same heads; meaning a C has 8 bolts also. Your engine is most likely not a C. There is a noticable difference in size, but you would only be able to pick up on it if you have some experience with these engines. Are you sure that the engine is 351 ci? A 302 and 351w are the same in appearance; as is a 351M and a 400.
Ernie
Ernie
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From: spartanburg, SC
351M/400 are considered smallblocks. There bore and bore spacing is the same as 302/351W. 351W smallblock heads bolt on. 385 series and FE heads don't fit, there too big.
302 and 351 are different too. 302 has 8.2" and 351W has 9.5" deck.
302 and 351 are different too. 302 has 8.2" and 351W has 9.5" deck.
Last edited by F150daniel; Jun 9, 2005 at 01:00 AM.
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From: Las Vegas
The two quickest/easiest way is look at the fuel pump........if the 2 bolts are horizontal it is a W. If the 2 bolts are vertical it is an M.
The other instant recognition is the thermostat housing...........if the thermostat is on the intake manifold it is a W. On the extended front of the engine it is an M.
The debate of big or small block will always go on..........my opinion is like stated above; the bore and bore spacing make the M's small blocks(they are the same as the 302/351). the heads will interchange with a few water passage mods.
In other words, nobody calls a 351W a big block because the block is physically bigger than the 302.
The other instant recognition is the thermostat housing...........if the thermostat is on the intake manifold it is a W. On the extended front of the engine it is an M.
The debate of big or small block will always go on..........my opinion is like stated above; the bore and bore spacing make the M's small blocks(they are the same as the 302/351). the heads will interchange with a few water passage mods.
In other words, nobody calls a 351W a big block because the block is physically bigger than the 302.
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Ford did not use the term big/small block back in the "old" days. They used engine families. Nevertheless the small/big block terms can be handy at times. The only thing "big block" about the 351M/400 is the transmission bolt pattern which matched that of the 426/460. This was done to allow a larger clutch to handle the torque produced by the 400 etc. There were a few "small block" 302/351W pattern 400's produced.
Engine Identification (rev):
======================
351C/M/400 335 series: 8 bolts in rectangular valve covers. Timing chain housing is part of block. Thermostat housing on block. Exhaust bolt holes diagonal.
351M/400 335 series: intake is 12.7" wide the 351C is narrow.
351W/302/5.0L 6 bolts on trapezoidal valve covers. Thermostat housing on intake. Exhaust bolt holes horizontal.
429/460 385 series: 7 bolts in rectangular valve cover
352/360/390/427/428 FE series: Intake goes under valve covers.
-There are other indicators but these are enough to distinguish engine families.
Engine Identification (rev):
======================
351C/M/400 335 series: 8 bolts in rectangular valve covers. Timing chain housing is part of block. Thermostat housing on block. Exhaust bolt holes diagonal.
351M/400 335 series: intake is 12.7" wide the 351C is narrow.
351W/302/5.0L 6 bolts on trapezoidal valve covers. Thermostat housing on intake. Exhaust bolt holes horizontal.
429/460 385 series: 7 bolts in rectangular valve cover
352/360/390/427/428 FE series: Intake goes under valve covers.
-There are other indicators but these are enough to distinguish engine families.
Last edited by Torque1st; Jun 9, 2005 at 02:14 AM.
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From: New Orleans
I've seen a small V8 in a 84 F150. I am guessing this is the 302? If so, my engine is much larger. I forgot to check the engine last night, but it rained also, so I wasn't outside much. I'll print this off and take it home with me to check tonight. So far, without dissassembling and basic engine knowledge, here is what I should check.
1) Valve Covers
2) Fuel Pump
Correct?
1) Valve Covers
2) Fuel Pump
Correct?
Postmaster
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From: Las Vegas
Originally Posted by myowneq
I've seen a small V8 in a 84 F150. I am guessing this is the 302? If so, my engine is much larger. I forgot to check the engine last night, but it rained also, so I wasn't outside much. I'll print this off and take it home with me to check tonight. So far, without dissassembling and basic engine knowledge, here is what I should check.
1) Valve Covers
2) Fuel Pump
Correct?
1) Valve Covers
2) Fuel Pump
Correct?
And/or the thermostat housing.........the thermostat housing is probably the quickest way to determine.
You say your motor is "much larger".........very few people I know can instantly tell a 302 from a 351W. (Hint: it's the distance between the top of the water pump inlet/outlet and the bottom of the head if you don't have a tape measurer.)
That being said, I'm guessing on you having an M. You're sure you have a 351?
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From: New Orleans
Actually, I got scrapping around the engine last night trying to count the valve cover bolts and I discovered the sticker saying it is a 400. I still counted the bolts. There are 8. I couldn't find the fuel pump in the dark.
Postmaster
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From: Las Vegas
Originally Posted by myowneq
Actually, I got scrapping around the engine last night trying to count the valve cover bolts and I discovered the sticker saying it is a 400. I still counted the bolts. There are 8. I couldn't find the fuel pump in the dark.
You're actually in worse shape than before..........
The sticker will read "351M/400" so now you'll want to know which one you have!! The only way I can figure on that(and I've never done it) is stick a soft, straight piece of plastic or wood in the spark plug hole and attempt to measure stroke......good luck.
At least you know it's an M.
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From: New Orleans
Well, most my questions are moot points for me either way, except for general knowledge. I have decided to get rid of this truck. I keep sinking money into it and it is not what I really want. I want a 4x4 manual and this is a 2x4 auto. Too much time and money to do conversion.
