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.

 

TMeyer, Inc. Precision Automotive Machining

You're welcome.

 

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

 

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

 

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.

 

Because according to the VIN number it is a 400

 

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 ?

 

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.

 

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.

 

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 ?

 

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

 

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

 

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

 

It is.