Old engine blocks. Do they go bad?

[karll]

I have a 1977 Chevrolet Heavy Half Ton pickup with a 454 big block. I am about to retire the truck because it's on it's last leg. Transmission/Differential/Gas tanks all have problems. The engine however still runs as strong as ever. I have plans to pull the engine and make a nice little hot rod out of it. A close friend of mine says that my block is probably warped and twisted from years of abuse. Is this possible. I have beaten on the engine, but it still runs great. I figured all I would need is a deck/plane it and hone the cylinder walls then add new internals. What do you guys think? Pardon me if this is the wrong forum, I didn't know where else to put it.

[drdisque]

no, blocks themselves rarely go bad and as long as it is running properly, chances are yours is fine. There are hundreds of blocks that are 70, 80, even 90 years old that still run beautifully.

[Moppie]

Cast blocks actualy age very well, and a well aged casting is usualy stronger than a new, freash one.

When you cast something it contains stress lines etc with in it, as the casting ages these stress lines work themselves out, and the piece becomes a little bit stronger, and much more reliable. i.e., if it was going to crack, it already would have.

For example, the old Peugot 206 WRC cars did not use the latest 2l peugot engine block, instead the team hunted around wrecking yards and collected several used blocks from an older generation engine, and used them to build the WRC engine. The idea being the older, cast blocks, had had a chance to de-stress, and so would be stronger and better able to tolerate the stress of being used in a Rally car.

[karll]

Superb. I didn't think it would go bad or warp or anything like that. Thank you for clearing it up.

[TheSilentChamber]

Obviously older iron blocks have the seasoning advantage mentioned above. One common problem that shows up is deterioration of the coolent passages around the cylinders, rust and scaling can make the walls incredably thin in certain spots. This isnt that common of a problem, but it does happen.

[karll]

I doubt there is anything you can do to aid a problem like that. I mean, it's not like you can add metal to places like that. I guess I won't know if it's a sound block until I strip it down and see for myself.

[CBFryman]

Originally Posted by Moppie

Cast blocks actualy age very well, and a well aged casting is usualy stronger than a new, freash one.

When you cast something it contains stress lines etc with in it, as the casting ages these stress lines work themselves out, and the piece becomes a little bit stronger, and much more reliable. i.e., if it was going to crack, it already would have.

For example, the old Peugot 206 WRC cars did not use the latest 2l peugot engine block, instead the team hunted around wrecking yards and collected several used blocks from an older generation engine, and used them to build the WRC engine. The idea being the older, cast blocks, had had a chance to de-stress, and so would be stronger and better able to tolerate the stress of being used in a Rally car.

very, Very, VERY good information

[kevinthenerd]

Originally Posted by Moppie

For example, the old Peugot 206 WRC cars did not use the latest 2l peugot engine block, instead the team hunted around wrecking yards and collected several used blocks from an older generation engine, and used them to build the WRC engine. The idea being the older, cast blocks, had had a chance to de-stress, and so would be stronger and better able to tolerate the stress of being used in a Rally car.

Wow! I thought about doing this myself, but I didn't think anyone was actually crazy enough to do it.

[karll]

So the block is strong and won't crack, but can it warp?

Edit: It has never overheated and the oil is changed at regular intervals.

[TheSilentChamber]

V motors generally do not warp. Accually most motors generally do not warp.

[2.2 Straight six]

Originally Posted by Moppie

For example, the old Peugot 206 WRC cars did not use the latest 2l peugot engine block, instead the team hunted around wrecking yards and collected several used blocks from an older generation engine, and used them to build the WRC engine. The idea being the older, cast blocks, had had a chance to de-stress, and so would be stronger and better able to tolerate the stress of being used in a Rally car.

another case of this happening was with the BMW-Brabham BT50 (i think) where instead of new engine blocks the team only used blocks from road cars that had done something like 110,000 miles. they were then reduced to 1.5-litre from 2-litre.

[TheSilentChamber]

Something for people not in the know... aluminum blocks do not require seasoning, it does nothing for them.

[2.2 Straight six]

is that the same for cast magnesium ones?

[TheSilentChamber]

Not sure, maby some one else knows... I personally have never seen a magnesium block, and have only heard of them a hand full of times.

[kevinthenerd]

Originally Posted by 2.2 Straight six

is that the same for cast magnesium ones?

Considering they're relatively new, I'm going out on a limb here and saying that there's insufficient aging data on these blocks, at least outside of a laboratory.

One thing worth mentioning is that Aluminum and Magnesium (and copper for that matter) don't have fatigue limits. Given an arbitrarily small stress with enough cycles, they'll all fail. Cast iron, however, does have a fatigue limit. Below a critical stress level, it's capable of handling an infinite number of cycles without failure.

I have a hunch that the atomic structure properties of these materials that cause the absence or presence of a fatigue limit are also responsible for the self-settling property that eases residual stresses.