I've got a 73 F-250 4x4. The guy I bought it from (who had it for a little while) said his uncle (who had it for decades) stroked the motor so it's no longer the original 360. Using the measuring tool in the spark plug hole method I'm getting a stroke of over 4 inches. I'm now not sure if it's a 390 or something bigger like a 410. Anyway, I need to put a new clutch in it. Being that the 360/390 is internal balance and 410/428 is external will it matter clutch wise? Can I put in a 390 clutch and be ok regardless of what crank is in it? I'm probably going to pull off the flywheel for a resurface when I do the clutch so can I tell what crank is in it by getting a look at the flywheel?

Also, what is a good clutch to use? I don't really want to use something from autozone. I saw this on summit, I'm thinking this would be a good street upgrade over OEM Zoom Performance Products MU7350-1 - Zoom MU Series Clutches - Overview - SummitRacing.com

Correct? Thanks

 

I would use a clutch for the 360/390. If your engine has a crank that is internal or externally balance, it will not efect the clutch.

 

I guess I just like to be sure, but I would start by checking the block #.

 

^^^Block number wouldn't make a difference at all if the internals were changed on a 360. The block number wouldn't decode as a 390 just because he swapped bottom ends. For all we know, it could be a 352 block built to a 410.

 

Thanks for the replies. I dropped the pan today and got the crank casting numbers and it turns out it's a 390. Just like the PO said it was. Casting number was 3U. Fordification has that as a 390 crank