What's the significance of those numbers?

 

Mainly that it is a post 1972, some say 1974, block. Some facts and possible speculation about the reverse 105:

332-428 Ford FE Engine Forum: WHAT IS A 105 BLOCK?

In any event, it seems you have a runner that was put together right. Keep the oil clean, don't rev the wee out of it and enjoy it!

 

Kind of resurrecting an older thread here, but after doing some looking at my truck today I noticed the heads have different casting numbers. Is that something that was commonly done? The one head is a C4AE head and I think the other is a C6AE head. Can't really tell if its a 8 or a 6 though. Thoughts?

 

There are differences in the heads. I found a bunch of threads on this and other forums about both heads. This one is the short version and sums it up:

https://www.ford-trucks.com/forums/5...90r-heads.html

I the grimy world of pickup truck engine rebuilds, a mismatch like that would not be uncommon. You have the "not my truck" mentality of some on the rebuilding side, and the "it's just a truck, I need it done as cheap as possible" on the owner side, with a little "they're all the same" sprinkled throughout.

Is your engine a performance job or "just a truck...". Does it pull hard towards the side with the C4 head under acceleration?*

Are you considering a rebuild or other work?




*not a real question, but you knew that

 

Kind of what I had read as well. Truck was rebuilt in the early 90's, after that sat in my grandfathers garage until last year. I think you hit the nail on the head with "not my truck". Only about 1000 miles on the rebuild. I hadn't planned on a rebuild for some time, but the mismatched heads concern me somewhat about the rest of the rebuild. I have not noticed any difference under acceleration.

From what I understand the C4 head is superior due to the high CFM it flows?

 

Very similar heads though from this chart:

C4AE-G C4AE-6090-G 64 FE Big Block Valves 2.02, 1.55 In port size 2.34X1.34 Ex port size 1.84X1.28

C6AE-R,C6AE-6090-R 66 FE Big Block Valves 2.02, 1.55 Int port 2.34 X 1.34 Exh port 1.84 X 1.28

 

I would say they are close enough for a non-performance pickup build or rebuild. The differences in the port location etc are in that other link I posted.

If it starts easily, doesn't make a blue cloud at start, doesn't leak or burn oil, idles, revs to at least 4000, is smooth, and gets 11 mpg or better, you are probably good.

 

Most pickups yes, but not all pickups used horizontal filter heads...

 

And 4x4's had a vertical filter