cracked block

[robert leazenby]

'70 LT-1, CTK, 350/370, Original motor. 49,000 miles on clock.

First off, the engine was running fine, using a little oil so I thought I'd work the heads. The heads ended up needing substantial work, but that's another story.

Compression check before removal yielded:
1-149
2-143
3-150
4-140
5-135; wet-140
6-140
7-135; wet-140
8-145

Upon cleaning the block for head re-install I noticed that number 5 and 6 cylinders had steel inserts installed and there was a crack going from the outside of the insert (What would normally be the cylinder wall) to one of the head bolt holes. #5's crack went from the insert and to the top thread only of the bolt hole. In other words, the crack was not all the way down the threads. #6's crack also went from the old cylinder wall to a bolt hole, but that hole has been bored out with a threaded insert installed. (Like a helicoil, but a solid threaded insert)

My dilema is what the heck to do. Were the inserts installed to repair the cracks, were the cracks caused by the inserts? Am I scr***d? Did I mention that the engine was running fine and I shouldn't have started this project.

I guess my question is, are the inserts a good fix for the cracks. Has anyone had experience with this type of block crack?

[John C.]

Re: cracked block

Just about anything can be fixed. Take your block to a machinist you trust (or comes highly recommended by someone YOU trust) and ask him to inspect the sleeves in #5&6. Ask your machinist to refer a welder if you don't know one. An original block IMO is worth going to extremes (read that as your checkbook) to save.

[Joe L.]

Re: cracked block

Robert and John-----

The installation of cylinder sleeves is an acceptable, and perhaps the only, method of repairing cylinder wall cracks. The sleeves will eliminate the effect of the crack and provide a better-than-new cylinder bore. That's because the nodular or ductile iron material used for most sleeves is superior to the gray cast iron of the original cylinder block.

The threaded inserts are an acceptable, and perhaps only, means of repairing damaged head bolt threads in the block. They will work for either stripped threads or threads which have been weakened by an adjacent crack, providing that the crack is not too extensive.

It sounds to me as if your block has previously been properly repaired. However, it might not be a bad idea, as John suggested, to have someone expert in such repairs take a look at it and render another opinion.