I was bored earlier today on summit racing and was looking for piston options for a 4" bore and between a 1.91 and 1.95 compression height. There were only 3 options, and only one of them (1.913 comp height) was for a 351m. The other two options (1.953 comp height i believe) were 6.9 idi pistons. Now, diesels usually have different reliefs cut into the pistons, but the 6.9 seems to have a similar combustion chamber to a gasser. The only real issues may be that it would have too much height (smack into the heads) and the pin bores are too large. Simple brass bushings for the bores would solve the second problem.

Now, this is just a theory. Anyone else have input on this? Could this be a higher performance, low buck option?

 

It's a hopeless engine, just get a 400 crank and be done with it.

 

x2, if you are deep enough into it to fiddle with pistons and rods, the easy way out is the 400 crank and aftermarket pistons.

 

Or, use 351C pistons and bush the pins.

 

I think that works in 400s. The compression height of a 351m piston is 1.921". The 351C, which has a lower deck, is listed as 1.63 or 1.635, same as a 400.

 

Sorry, I didn't explain. I meant use the 351C pistons in a 400 with bushed pins. Not in a 351M.

 

I shoulda knowed you knowed that based on previous posts which I din't check sorry it will happen again thanks.

 

No need to apologize. As soon as you said that and I went back to look at my post I smacked myself in the head. Doh! That's not what I meant! My bad.

 

. Yeah, I went through the whole Silvolite piston catalogue (very extensive) one day looking for something that made sense for 351M's and 400's and the 400" with 351C piston modifications are the only things that make economic sense... unless you want to go full custom 351M pistons... but for that money or less can have a great 400" engine... or some kind of longer custom rod to get the 351M pistons up higher in a 351"... Hot Rod Magazine did a combo of all that (Chevy rods, Chrysler pistons, etc.) in one of their 400" builds, but ended up with like $6,000 in just the basics...