I have been trying to do some google searches but am still confused. My block is a D1AE-6015-A2C. From my homework this is a 400 motor. Is there anyway to verify that easily?

 

Probably a 400. Unlikely anyone would have rebuilt it as a 351 a some point but stranger things have happened. What state of assembly is it or is it in a vehicle?

 

It's in a 78 F250.

 

Pull a spark plug. Bring that cylinder to TDC. Take a wood dowel put it on the piston and mark it. Move the piston to BDC. Mark the dowel. Measure between the marks,4 inch stroke = 400. 3.5 inch 351M. Easy.

 

Thanks. I was going to do that just lazy. Ah

 

Hard to do on those motors according to the propaganda surrounding them but worth a try. Maybe a replacement engine but I still can't see anyone rebuilding it as a 351.

 

Thanks for the input.

 

85E, there are thousands of guys who will just do a stock rebuild or a rebuilt engine from the parts store. If they're not car guys they won't even know it's possible. Or if they're the typical guy behind the counter at the chain auto parts store. "Was that F250 a Ranger or a Ranger XLT?" The computer leads them around by the nose. "Sure, I'll have to order it."
Or the auto shop owner who probably knows but probably won't mention it because it'll complicate matters and he knows the truck owner is looking at price. So he does a stock rebuild because that's the easiest way for him to get work and be paid for it.
Or the owner is asked the question and thinks the 351M eats a ton of gas and the 400 will eat more. "No Thanks!"

Now if the owner asks about more power the private shop owner will start talking 400 and the parts store guy will look in the book and say there's no HP version of this engine, sorry.
That's the real world.

My truck was a 351M and was rebuilt as a 400. The last owner didn't know that, he only knew it was a 400. It took me discovering the difference in clutches to get me to look at the VIN and see that it was originally a 351M. That's probably when it got the Edelbrock Performer intake and Holley 4-barrel. When I took the engine apart I measured the stroke and found 4", then I knew for sure.

R.

 

Only for sure way to know is to drop the oil pan and look at crank casting. 1K Is 351m and 5m,ma,mab are 400s.

 

Could have been done by a commercial rebuilder. They were bad about lumping parts in a bin then pulling them out at random to reassemble engines. The OP should look to see if there's a reman tag somewhere on the block. If there's not, it's more'n likely a 400.