New Block Tempering - Expansion & Contraction

[Dieselboy]

Doc,

There's always been the story, and the article covering your engine build further confirms, that there's something about using a seasoned engine block versus a new one.

A few years ago when I was doing research for our engine project, I remember hearing from several engine builders that after a new block has warmed-up and cooled-down several times it is 'stronger' than when it was new.

My question is this:
What metallurgical process takes place during an engine block's formative miles that makes more desireable than a new block?

Sub-Question:
Is the block actually stronger (tensile strength), or is another characterization more accurate - superior impact properties?

Sub-Sub-Question:
Is this Aggie looking too deep, again? ;)

[CleviteKid]

I believe there are two factors at work in the cast iron blocks.

The first is resisdual stress relief. As the block heats and cools a few times, the areas of highest residual stress will yield slightly, reducing the stress and thus reducing the potential for further cracking.

The second is proof testing. If a block is going to crack, better that the rich guy who bought it new has to argue with the dealer over the replacement. Us poor schmucks who have to buy used and rebuilt at least have had the blocks proof-tested and if we are observant, we only buy non-cracked non-leakers.

Another phenomenon entirely is at work with all Aggies - you know so little when you arrive at college that anything you learn seems amazing to you :D !!

Keep on truckin', Dr. Lee :cool:

[Jim Brzozowski]

There is also a third bonus in using a block that has been thermal and stress cycled. Once its taken a set it won't tend to move around much anymore so if you rebuild one of those or build one up for more HP the cylinders will stay round where as an unseasoned block will go through the transformation stage and you may not have the best ring seal that you otherwise would get from the seasoned block. Everyone knows the better match between the rings and the cylinder the better the seal.

Have a great day.

[grape]

my block crank and rods are at the cryo place right now.