Thread: is it a big block?

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I've recently pulled my engine in my 81 F-250 to put a different engine in. i noticed that the engine i pulled is bigger in size than the other engine and won't bolt up. Is my original engine a big block?

where would the block numbers be

Just to show my ignorance You mean to say Ford dosen't have the engine code numbers on the block like GM ????

You can tell how many Fords I've worked on.

numbers on the valve cover sticker are 5F575AP

I'm not sure if it is the stock engine. My VIN says its a 351W and the guy I got it from said it's a 351M

Check the block numbers.It probaly is a 351m,some one pulled out the 351w,and put it in its place and got rid of it.

My "new" engine is supposed to be a 351W but the old one is wider both where it bolts up to the tranny and in overall size

i don't know if it makes a difference or nopt, but the old engine is a 2 bbl

i've seen 460s with 2bbls and small 200 l6s with 2bbls.... ok check on the block where the starter mounts there should be a flat spot with some numbers.... read off that code

Originally Posted by thesals

i've seen 460s with 2bbls and small 200 l6s with 2bbls.... ok check on the block where the starter mounts there should be a flat spot with some numbers.... read off that code

200 I6's only came in 1bbl's, in America anyway

Originally Posted by Matt167

200 I6's only came in 1bbl's, in America anyway

on old cars what you have and what it came with can be totally different seeing that people modified them the day they bought them sometimes..... but yes stock they have 1bbls

351M Is considered a big block, 351W is a small Block. Big block 460,428,427, 390 should bolt in.
You might have to change motor mounts.The 400M will bolt right in, same block as the 351M just differant crank and rods inside. They are both related to the 351C. they use the same heads but the blocks are differant.
The crank and rods won't fit the 351C and the Intake won't fit the 351C from
the 351M or the 400M. I'd drop a 400M in, and find some closed chamberd heads from a old Cleveland motor. Slap those heads on and that motor will make gobbs and gobbs of horse power.

Kurt

Buy the ford Performance book and read the section on 351C 351M 400M, it will tell you every thing you need to know. Kurt

Originally Posted by vara4

351M Is considered a big block, 351W is a small Block. Big block 460,428,427, 390 should bolt in.
You might have to change motor mounts.The 400M will bolt right in, same block as the 351M just differant crank and rods inside. They are both related to the 351C. they use the same heads but the blocks are differant.
The crank and rods won't fit the 351C and the Intake won't fit the 351C from
the 351M or the 400M. I'd drop a 400M in, and find some closed chamberd heads from a old Cleveland motor. Slap those heads on and that motor will make gobbs and gobbs of horse power.

Kurt

Sorry, but if you had a 351 M in there, there is NO WAY a 390, 427,428 is going to bolt to that C6. (completely different bolt patterns). From what you have said, you could realistically do 3 things:

1.) Find another 351M / 400M and install it.

2.) Find a 351W C6 tranny (truck) and swap both the tranny and the motor.

3.) Do what I did and ditch the 351M, and the 351W, and install a 460. It will bolt up to your existing M trans. and factory parts are available to make this swap easy. The torque difference is INCREDIBLE.

Hope this helps you out, Snake.