I swapped out my 305TPI a couple months ago, and gave it to my friend to put in his s10, except when we went to change the intake gasket I noticed its cracked badly above the lifter valley on the cylinder water jacket on BOTH sides! The motor only had about 65,000 miles on it, and had a mysterious coolant leak that all makes sense now.
So my question is, what usually causes the cracks? overheating (it did a few times) or Cold?(couple times it would dip down to minus -30 and i didnt plug it in ) I say heat, my friend claims cold

 

Probably froze it up. Lifter valley cracks from a frozen engine are common for many types of V8s (not just Chevy).

 

my guess would be stress from head bolts, at any rates it's common on SBCs. weld it or trash it as common as a 305 is it won't be hard to replace.

 

It just happens.

 

Does the crack go vertically or horizontal?

 

Mexico block. Junk!

 

Mexicano? Aye Carumba!

 

there was a bad batch of castings. I never saw one but, heard that some of the truck owners had to have the eng, replaced under warr. may have been the same casting

 

Yep. These blocks are also bad for threads pulling out of the castings. I had to helicoil one of these mexico blocks and install a head stud kit to save the block. Of course this problem couldn't have been noticed BEFORE all the machine work was finished. NOooooooo.......

 

Anyone happen to know the casting numbers (or year/model/engine type) so we can stay away from these in the future?

 

'87 LB9 with cracked lifter valley here.

 

Where does it crank? Is it a horizontal one or vertical? Above the lifter going to the head or what?

 

My 86 block was cracked. Just a bad casting.
Not frozen, from Mexico, or anything else weird, just a factory flaw.

Didnt have any coolant problems, but I did have an uncureable cooling problem and the passenger side ran 200 degrees hotter than the driver side.

 

Just below the bottom of the bolt hole castings. Horizontal, one on each side.

 

Early to mid eighties casting. Just about the time of the first wave of work was sent to mexico, teathing pains I guess.

 

I've torn down at least two early-mid-70s 350 blocks that ended up having visible cracks in the lifter valleys.

If I remember correctly, one was from a '73 or '74 Impala and the other from a '77 truck.

The engines were torn down in the early-mid 1980s and were original to the vehicles.

jms

 

when they switched to the 1 piece roller design, they didnt tap the head bolt holes all the way, so that when the heads were tightened down it would crack the block. im not sure what models had this problem, it was something my instrutor told me about that he dealt with when he was tech