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-   335 Series- 5.8/351M, 6.6/400, 351 Cleveland (https://www.ford-trucks.com/forums/forum54/)
-   -   351 or 400 crank? (https://www.ford-trucks.com/forums/931586-351-or-400-crank.html)

1980 Ford F-250 02-17-2010 09:16 PM

351 or 400 crank?
 
Okay, I bought a 1980 ford f250 and the guy i bought it from said that it had a 351m in it. I went a looked at the vin number and it said that it had a 400 in it, but when i pulled the engine apart it had 351 stamped on the pistons. So we bought a 400 crank for it and built it to be a 400. Now i have a reason to believe that it was a 400 to start out with. I still have the original crank and if it is a 400 is it worth any money? Is there a way that i can find out if it is a 351 of a 400 crank?

Thanks in advance.

zaaac 02-17-2010 10:09 PM

TMeyer, Inc. Precision Automotive Machining

You're welcome.:)

mark a. 02-18-2010 07:32 PM

If the pistons were stamped 351 on the sides why would you think it was a 400 ?

85e150 02-19-2010 12:29 AM

If the crank is out of the engine, 3.50 vs. 4" stroke should be easy to figure.....

mustang81 02-20-2010 01:00 AM

Mesure the distance between the center of the crank to the center of the connecting rod. 4" is a 400 and 3.5" the 351m. The 400 as a ridge of about 1 inch at the first conterweight on the front you can feel with your fingers. The 351m don't have it. Also the 400 have 5M, 5MA or 5MAB casting number on the first conterweight. My 400 crank have 5MAB.

1980 Ford F-250 02-20-2010 02:19 AM


Originally Posted by mark a. (Post 8533898)
If the pistons were stamped 351 on the sides why would you think it was a 400 ?

Because according to the VIN number it is a 400

mustang81 02-20-2010 03:02 AM

Maybe you have a 400 with 351c flat top piston ? wich is good to raise your compression with stock head. stock 351m and 400 have dish piston. Can you post a picture of the top piston ?

1980 Ford F-250 02-20-2010 08:28 PM

I dont have the pistons anymore and i didnt take any pictures of the old ones. From what i remember, i dont think they were flat top, but i could be wrong.

1980 Ford F-250 02-21-2010 12:40 AM


Originally Posted by mustang81 (Post 8539307)
Mesure the distance between the center of the crank to the center of the connecting rod. 4" is a 400 and 3.5" the 351m. The 400 as a ridge of about 1 inch at the first conterweight on the front you can feel with your fingers. The 351m don't have it. Also the 400 have 5M, 5MA or 5MAB casting number on the first conterweight. My 400 crank have 5MAB.

What if there is just a 5 on the second counter weight from the back?

zaaac 02-21-2010 01:05 AM


Originally Posted by 1980 Ford F-250 (Post 8542694)
What if there is just a 5 on the second counter weight from the back?

Did you look at the picture on the TMeyer website? That's all you need to figure out if it's a 351M or 400 crank.

mustang81 02-21-2010 12:15 PM

Look at zaaac first post to identify your crank, perfect pics. 5 on the second conterweight from the back don't tell me anything, maybe connecting rod # 5. Are you sure your looking at the conterweight ?

Scolesy8 02-21-2010 01:00 PM

personally, on a truck that was built in the 70's, i have learned from experience dont go on vin# and what was original. over 30 some years old so things are changed. my vin said it was a 400 when i bought it, but it had a 351 in it. but i ended up swappin over 2 a 400 to start out a build on. just my 2 cents though

85e150 02-22-2010 10:24 AM


Originally Posted by mustang81 (Post 8539307)
Mesure the distance between the center of the crank to the center of the connecting rod. 4" is a 400 and 3.5" the 351m. The 400 as a ridge of about 1 inch at the first conterweight on the front you can feel with your fingers. The 351m don't have it. Also the 400 have 5M, 5MA or 5MAB casting number on the first conterweight. My 400 crank have 5MAB.

Crank throw is 1/2 the stroke. Crank centerline to rod journal centerline will be 2.0" and 1.75" for the 400/351.

1980 Ford F-250 02-22-2010 11:03 AM


Originally Posted by zaaac (Post 8542736)
Did you look at the picture on the TMeyer website? That's all you need to figure out if it's a 351M or 400 crank.

I did. Is the 400 crank the one on the right? If it is, that is what my crank looks like.

zaaac 02-22-2010 11:24 AM


Originally Posted by 1980 Ford F-250 (Post 8548480)
I did. Is the 400 crank the one on the right? If it is, that is what my crank looks like.

It is. :-dancing1


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