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What’s the difference between the 351 engine and the 400 engine? And why would someone want to replace their 351 with a 400?
 

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The 400 is a mid block ford while the 351w is a small block. I get mixed up on 351 C and 351 M blocks, but one shares the same block with the 400 and 391 blocks. And why would you want to change? HP buddy.
 

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Depends on which 351 / 400 you are talking about.

If you are talking about the older Bronco - you have the 351M and the 400. They share the same block. Now I'm not a Ford engine expert by any stretch (I cut my teeth on small block and big block chevy's with some pontiacs thrown in for good measure) ..........I'm sure @cobrajoe could school you pretty quick....

But the quick and dirty.

The 400 was Ford's stop gap to replace the FE big block (390 etc) when the middle late 70's EPA stared mandating pollution control, oil prices spiked and gas mileage started to become a factor.

From my understanding the 351M is the same block as the 400 - in essence a destroked 400. And if I remember correctly both were loosely based on the 351C (Cleveland) engine.

From a pure power standpoint in factory configuration there wasn't MUCH DIFFERENCE at all between the 351M and the 400.

The 351W (Windsor) took over for the 351M/400 in the early 80's.
 

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351M uses a 3.5" stroke crankshaft and taller pistons; 400 uses a 4" crankshaft and shorter pistons. Both share the remaining hardware. They are part of the 335 series engines.

I was going to stroke out my 351M to a 400 but finding a 400 crank hasn't been easy. It's great to pick up 49 cubic inches just with a crankshaft and piston swap.

Both suffer from low compression that takes some effort to increase. There is not a ton of aftermarket support for them either.

My 351M has an Edelbrock intake and 1406 carb on it. It actually does good at getting the Bronco up to speed. It won't win any salt flat races, but it's adequate. One plus of the 400 is I've read it is the longest stroke engine Ford made, so it is good for torque.

They get a bad wrap as children of the smog era, and they are significantly handicapped from the factory. The potential is there, but it takes some money to unlock.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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The 400, 351M, and 351C are all 335 series engines. Meaning they had a 3.35" base stroke. They all share the same 4" bore as the 302, 351w, and 300-6. The v8s all share the same bore spacing as well. The Cleveland was the first of the series, then the 400 came out to replace the 390FE. The 351M was a 4 year engine from 78-81 and is the "loser" of the bunch. The cleveland came with 2 styles of head here in America, the 2bbl and 4bbl heads. The 4bbl head is really only good for HIGH rpms.

However, with a bit of generic hotrodding, the 400 or 351M can be a screamer. Slap some early 2v cleveland heads on, boost the compression, slap a cam in and a 4bbl carb on top, and you'll have a good healthy engine.

Another thing about factory stroked or destroked engines. The 351M is a destroked 400, as noted above. The Cleveland is a short deck block and isn't directly interchangeable. Pay attention to cam specs. When they list an rpm range, find out what engine that is for. For instance, the 300 inline six IS a factory stroker of a 240 inline six. Same block, just different rotating assembly. Cams for the 240/300 are spec'd out in 240s. If you put it in a 300, the rpm range shifts down about 1000 rpms. My 300 cam has a range of 2400 to 6800 rpms, but thats in a 240. In my 300 that range is now 1400-5800.
 

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See..... you guys don’t need me.
Don’t forget, even though the Cleveland is part of the 335 series, it uses the small block (289/302/351W) bolt pattern & the 351M-400 uses the 385 series big block (429/460) bolt pattern. Also, to confuse you even more, the 351C has a dry intake, and the 351W uses a wet intake, even though they are the same displacement..

EDIT: should be Windsor not M
 

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^^^ thats why you have to make a coolant passage when you install cleveland heads on a windsor or 400 block. A pair of chopped up cleveland heads will also fit on a 300 inline six...

Also, the 400 or 351m never came with a factory 4bbl. Only 2 bbl carbs.
 
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See..... you guys don’t need me.
Don’t forget, even though the Cleveland is part of the 335 series, it uses the small block (289/302/351W) bolt pattern & the 351M-400 uses the 385 series big block (429/460) bolt pattern. Also, to confuse you even more, the 351C has a dry intake, and the 351M-400 uses a wet intake, even though they are from the same engine family.
I know the 351M/400 intake is dry and it appears the Clevelands are too. My water neck is on the block just in front of the manifold. I thought the location of the water neck was one of the telltale signs separating the 335 series from the Windsor group?
 

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Sub'd because I have all these 400's to deal with.
 

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I know the 351M/400 intake is dry and it appears the Clevelands are too. My water neck is on the block just in front of the manifold. I thought the location of the water neck was one of the telltale signs separating the 335 series from the Windsor group?
Correct, sorry should have been W not M.


In all serious, at my age, I should probably should not take my phone and just wait till I get home and do it on my computer. Editing just doesn’t work for me on the phone
 

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I know the 351M/400 intake is dry and it appears the Clevelands are too. My water neck is on the block just in front of the manifold. I thought the location of the water neck was one of the telltale signs separating the 335 series from the Windsor group?
Thats correct. Also, the timing cover on the windsor is 3 dimensional. On the cleveland, its more of a flat plate and the timing chain sits back in the block a bit. Basically the 2" thickness of the windsor timing cover is built in to the cleveland block. And they all have the CP cleveland casting mark on said extension. Though 302s also have the CP marks from being cast in cleveland.
 

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CP or CF (Cleveland Foundry)?

While denoting the differences and potential issues between the 351M and 400's... you guys might want to repeat the water jacket crack issue, specific to the early 400's with the MCC (Michigan Casting Center) blocks.

An old but informative site with relevant info... at least, some of it was saved.
 

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Cleveland foundry but looks more CP then CF. Interesting symbol.

Bubba’s page is a great reference.
 

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If someones needs a 351C, I have a '70 2 bbl. w/ a C4 I'll let go cheap. I'm cleaning house; sold two 427's today.
 
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