I have a 351 cleveland and I want to bolt a C6 up to it. Is there a difference between small block C6's and big block C6's? I have a chance at a few but they were both previously bolted to big blocks. Thanks

 

CanadaMike, there are 3 differant cases that I have seen so far, first the FE case, the the 385 series case, and then the 6 cyl and small block. The internals are largely the same. I haven't seen a C6 behind a 351C in a factory application, but the local salvage yards here have lots of them behind 300 inline 6s, which would bolt to your 351C just fine. Look in full size 2wd trucks and vans. DF

 

I think all the 4Bbl Clevelands with ATs had C-6s mounted to them. I have a C-6 that was factory mated to a 2Bbl Cleveland in a Cougar; '72, I think. Small block C6s are somewhat scarce, but not what I'd call rare. Check out the local wrecking yards and attend a few swap meets; you should be able to find one. I'd sell mine, but I wouldn't want to go thru the hassle of shipping it.

 

There are a lot of sb C6 trannys in salvage yards in vans behind I6 and sb V8 engines. Should not be hard to find one. I have seen many 70 Mustangs with 351C and FMX transmission. So many that I thought this was standard. I have replaced FMXs with sb C6s.

 

if you are running a 302 or a 351W the bell housings are the same.
If you are running a 351C or a 390 or 460 the bell housings are the same. you can not bolt the C-6 from the 302/351W to a 351C.
But you can interchange the insides from the big and small block C-6's
the torque converts will bolt up in either bell housing.

 

"if you are running a 302 or a 351w the bell housings are the same.
If you are running a 351c or a 390 or 460 the bell housings are the same. you can not bolt the C-6 from the 302/351W to a 351c.
But you can interchange the insides from the big and small block C-6's the torque converts will bolt up in either bell housing."

I am having a little problem with the post from AZ4x4f150 above. There are so many different bolt patterns that I sometimes have to stop and think about which ones interchange myself. My recollection is this:
I6,289,302,351W, AND 351C interchange
332, 352, 360, 390, 410,428 interchange
351M, 400, 429, 460 interchange

These engine bolts patterns DO NOT interchange between groups.

I am getting on in years. My memory could be failing. You might want check with others for confirmation.

 

DavidB, You are almost 100% correct. Some of the earliest 400's had the small block bolt pattern. A friend of mine told me he had one.