So tonight i go through the effort to start to taer apart a block to take up to the machine shop tomorrow so i can get my 400 build wraped up (heads are done rotating assembly has been prep and ready to go, just need to get the intake situation sorted out my holley 750 upgraded for free by a local drag racer, and a few other little nick nacks). Anyway i know that the best years of blocks are the 71-74 and 80 and newer blocks, and as such i have gone through 5 blocks now as the block i started to take apart tonight is a 77 block that came out of an 80 f-150, which we thought to be an 80 block.

2 of the other blocks were another 77 (which is currently sittin up at the machinest as we didn't know about the difference in years) and a 78, one other was a 72 but was never serviced and a broken crank that banged up the bottom end to a point where i'd be hesitant to use it for what i plan on, and the remaining block was of the right year but after i got it disassembled and while i was pressure washing it off i noticed that 2 of the lifter bores were cracked, so a no go on that one.

Now the point, what exactly is the difference between the years (71-74 & 80 and newer vs. the 75-79 blocks)? What i was told was that the oiling sytem on the 75-79 blocks were restricted and for what i;m doing would be a bad way to go (roughly 425hp 450tq for my comp mud bogging truck which sees minute longs runs at 5500rpm in deep nasty mud with big tires).

 

i've not ever heard that? are you sure you don't mean the 1975 D5 heads are restrictive in the exhaust ports?

where have you heard of the restricted oil system?

 

A local machinest knows of it and a 400 guru we met that uses 400's in demo derby car has had issues caused by it and we've also run accross numerous reliable articles making mention to it.

 

The only difference I have ever heard of are some extra beef in the valley on later blocks to prevent cracking.

 

check with Tim at Tmeyer, this forum's sponsor, and confirm, but any block can be modified with or without the oil restriction. I know Moroso makes an oil restricter kit and
I remember reading about reducing restrictions by enlarging a few select oil passages and drain holes. I, too, thought the later blocks just had more material added in some high stress areas.

 

This is good reading.

 

after buying my early 77 highboy with a 351m I found this site and started learning about that engine.

One of the things I discovered was that there was a series of bad castings produced by one plant for a period of time.

As I recall there was a symbol stamped on the block which indicated the plant and date of manufacture. I checked mine and it wasn't one of the questionable blocks.

I just tried to find that info again and was unsuccessful. I hope some of the other users of this site respond with more info for you.

Don't rule out a 77 78 79 block

 

I believe it's the heads that are susceptible of cracks. latter 70's blocks had more beef in the #3 main-bearing area.

 

I've got my 400 build book right here. The problem 335-series blocks are those cast at the Michigan Casting Center before March 2, 1977. That means blocks cast with a date code of 7C01 or earlier at the Michigan foundry are the trouble blocks. A block cast in Michigan is identified by an MCC logo at the back of the block by the oil sending unit.

These blocks suffered water jacket cracking in the lifter valley. According to my book, the cracks will be horizontal and about an inch above the lifter bores.

 

Actually its not the cracking issues with the early blocks, from what i learned about the cracking issues (did some reasearch when i put a 71 motor into my truck which i'm currently running) is that if it hasn't cracked by now then it shouldn't be an issue, and from my knowledge of metalurgy this should hold true, as if not we'd still be hearing of the cracking issues.

What i found out after i talkeed to the guy that initially told us (he's a ford engine builder in his own time and high up parts guy with access to all of ford parts numbers) is that the late 70's (77-78 seemed to be the worst for it) blocks had the oil galleriers to the mains restricted a good bit to a point that if i were to use for my application i would have to rework the oil galleries so i don't cook a main bearing. Now if someone has some more thoughts or proof on this please post up (if you have spefic casting numbers please post them up, i got some when i was talking with the guy today but i have to gt them sorted out so i don't get them all confused).

I also found out that the 400 blocks were a stronger block than the 351m block and if you are searching for performance application its best to go with a 400 block.

 

I forgot to mention that not every block from that foundry and time period is cracked. Many of the blocks are perfectly fine. It's simply an issue that should be checked for when looking over a block, just in case.

 

Most of this stuff is brand new to me. I think the best way to start is to copy down all the known block casting numbers and take them to the source of these claims. 351M blocks are the same as 400s.
http://home.earthlink.net/~bubbaf250/parts/parts02.html

 

identical, same cast codes, same foundries, same blocks. if there were blocks with oil restricted mains, all that would be needed to do is ream the oil passage from the main saddles to the lifter galleys.

 

Brian, that site has been the one site or even book that has had the most correct information i've seen, as i was reading a book, high performance ford parts interchange, and at least 75% of the information in that book about the 400/351m was incorrect. Lol now that i look at that site, i have looked at blocks with the casting codes from all but the small bellhousing bolt pattern 400's.

 

fmc 400 is right.It was cast at one of 2 ford foundries, the cleveland foundry or the michigan casting center.those cast at the mcc prior to march 2,1977 experienced water-jacket cracking peoblems immediately above the lifter bores due to an internal coring problem.the magic date is in code form 7C01.