351M/400 inter-changeable?
Senior User
Joined: Sep 2003
Posts: 364
Likes: 0
From: Hartland, MI
Any as long as you change enough junk
The 315M and 400 are two different engines
Well a 351M or a 400 are the only direct bolt in's. The 460/429 share the same bellhousing, but accessories and mounts are different
The 315M and 400 are two different engines
Well a 351M or a 400 are the only direct bolt in's. The 460/429 share the same bellhousing, but accessories and mounts are different
Senior User
Joined: Sep 2003
Posts: 364
Likes: 0
From: Hartland, MI
If there is a sticker under the hood it will usually say Engine Family 351M/400 and then after that or next to that it will say Eng CID 351M or 400 depending on what you have CID means Cubic Inch Displacement If the sticker is not there I dont know of another way to tell if its a 351M or a 400 besides tearing a head off and measuring the stroke
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Welcome to FTE!
There is no way to find out except to measure the stoke. If the engine is original in the truck the VIN code will list the engine size. Check out the Read First: FAQ thread at the top of this forum for VIN number information.
There is no way to find out except to measure the stoke. If the engine is original in the truck the VIN code will list the engine size. Check out the Read First: FAQ thread at the top of this forum for VIN number information.
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Posting Guru
Joined: Dec 2002
Posts: 1,346
Likes: 4
From: missouri
what are you asking which motor you have
measure the distance between the top two transmission bolt a 302 351w are closer than the 351m/400 460 429
measure the distance between the top two transmission bolt a 302 351w are closer than the 351m/400 460 429
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New User
Joined: Jan 2005
Posts: 24
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From: Crete, NE
on a 351 M the thermostat housing is seperate from the intake manifold bolts vertical pointing towards the top tank of the radiator at an angle, the winsors comes out pointing straight up bolts horizontal. but the only way to visually tell if it is a 400 or 351m is crack the heads off that baby. Also heard that the 400 harmonic balancer is thicker. don't know if it is true.
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
No, the harmonic balancer is not the same between the 400 and 351M. The 351M will fit onto a 400 crank but it is not the same balancer. For long engine life, you should have the correct balancer for the engine.
The only difference between 351M and 400 are crankshaft, pistons and harmonic balancer.
I have no idea how you would tell which one it is without pumping the volume on a cylinder.
Good luck,
Doc
The only difference between 351M and 400 are crankshaft, pistons and harmonic balancer.
I have no idea how you would tell which one it is without pumping the volume on a cylinder.
Good luck,
Doc
Tuned
Joined: Mar 2004
Posts: 454
Likes: 0
Well, you ask around and you will get different answers to that. Some mechanics tell me it is the same...some tell me it is not. You say it is different, but several others in this forum say it is not. So who knows, really....
I guess the machine shop could have changed mine without my knowing. It looks VERY similiar, though
I guess the machine shop could have changed mine without my knowing. It looks VERY similiar, though
Junior User
Joined: Mar 2004
Posts: 87
Likes: 0
From: Texas
if the only difference is the stroke why not just put #1 on tdc and pull the spark plug off and then put a little rod down and mark where it is and then do the same to #4....mark the difference and there ya go?
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