I was reading on the big bronco web site that
some of the early 400 blocks were prone to cracking?
if you had a cleveland foundry block you were ok.
if you had one from the michigan foundry you could have
problems. He gave a picture of the foundry marks as being
mcc and mcf. well mine does'nt have either mine looks like
a 3 with the tips curled around. anyone heard anything
about this problem or know what this mark is?

(the date code was 1k16 on the block below the mark)


THANKS, YOU GUYS WERE AWESOME ON MY OTHER POST

 

I have that engine and have no cracks but what your looking for is a M with a C below it and a c inside it. They were on the 1977 and newer thats what I have in my 79 but I had mine checked by my machinest he said no cracks so I rebuilt it.

 

where are they?

 

By the oil sending unit you will have to scrape it down to see it well if there was any leaks there.

 

thanks!

 

that's the factory sending unit behind the intake? i didn't see any there - will look again. the only number i found on my block is a D4 casting no. - the valve cover sticker has a D6 number, carb has a D5 - supposedly it came out of a '78 LTD or something, but the D6 on the valve cover is the newesr no. i've seen on it...

looks like it MAY have 351c 2v heads - or else my "2v 351" heads are really 351m/400 heads... are there any #'s to tell them apart? none of the books i have mention the 351m/400 heads being different from 2v 351c heads, and if both pairs i have are the same, then i have nothing to compare to tell which kind they are.

 

[updated:LAST EDITED ON 13-Aug-02 AT 00:50 AM (EST)]Yes the mark is at the factory sending unit. A lot of times the marks are hard to see but I will say they are there. I didn't see mine very clear until I got my block dipped at the machine shop you might try to get a small wire brush back there to clean it. I had my block checked for cracks and none was found. The D5 stands for 75 D6 is 76 but what you would be more interested in is the block number and it is at the starter just above it on the block tell me that and I may can tell you what you want on your block as far as the year. The 351M/400 head numbers are under the valve covers.

 

the 400 block has "D4AE" and what looks like "B2A" back by the starter. by the sending unit, i saw a ford logo, a big "12", something that looks like a riveted-on tag but is actually cast in and probably had a date code or something on it, and a "C" with a little "c" inside it. there was something next to that. it didn't look like an "M", but it was hard to tell.

i didn't get the intake & heads off last weekend, but i think they are the ones that came on the block...

 

 

sounds like a michigan block

 

>the 400 block has "D4AE" and what looks like "B2A" back by
>the starter. by the sending unit, i saw a ford logo, a big
>"12", something that looks like a riveted-on tag but is
>actually cast in and probably had a date code or something
>on it, and a "C" with a little "c" inside it. there was
>something next to that. it didn't look like an "M", but it
>was hard to tell.

Here's a picture of the Cleveland Foundry (CF) mark located behind the o.p. sending unit:

https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=7564&.jpg

 

[updated:LAST EDITED ON 14-Aug-02 AT 01:56 PM (EST)]>sounds like a michigan block

it definately does NOT look like the CF block above... is that an oil bypass line i see?

are michigan blocks the ones that crack in the lifter valley?

are there any differences in cylinder wall thickness?

 

>>sounds like a michigan block
>
>it definately does NOT look like the CF block above... is
>that an oil bypass line i see?
>
>are michigan blocks the ones that crack in the lifter
>valley?
>
>are there any differences in cylinder wall thickness?

Yes it is an external oil line, the MCC blocks cast prior to March of '77 are prone to cracking in the lifter valley, I've never heard of any difference in the cylinder wall thickness.

 

[updated:LAST EDITED ON 15-Aug-02 AT 03:06 PM (EST)]how bad are these blocks - are we talking like 75% of them crack by 100k miles, even totally stock, or is it more like at a certain horsepower level it will crack instantly, or in 2 years or less?

i've got a '77 cougar that's been sitting in the garage for almost 20 years. it has a 351M with about 90k miles on it. it's been whispering to me that it wants a mildly warmed-up 400 put in... what are the chances THAT block is a good one?

(can't get to it now - car is buried under/behind a lot of stuff...)

 

>how bad are these blocks - are we talking like 75% of them
>crack by 100k miles, even totally stock, or is it more like
>at a certain horsepower level it will crack instantly, or in
>2 years or less?
>
>i've got a '77 cougar that's been sitting in the garage for
>almost 20 years. it has a 351M with about 90k miles on it.
>it's been whispering to me that it wants a mildly warmed-up
>400 put in... what are the chances THAT block is a good
>one?

It would seem logical to assume that if a particular block was going to crack that it would have already but I know of a guy who just poured quite a few $$$ into a rebuild on one of these blocks last year and had it crack on him within 500 miles. It was a little warmed over but not a really hi-po rebuild. I'd be really wary of rebuilding any pre-77 Michigan cast block. IMHO you'd be better off finding a later year or even better a Cleveland cast unit.