Kind of an interesting thought

I know of car companies that buy back, or replace a very old car with say 750,000 kms on it to see how it's held up so well. I haven't heard about your story but if engines only become stronger, then why are their more failures with older engines?

 

i don't think there are many block failures in older engines.

 

There are a hell of a lot more cracks in an older engine than a new one.

 

A friend of mine builds racing engines. Mainly small block Chevys for circle track stuff. But I remember him saying that blocks move around some. But by 100K or so they have stabilized so when you bore them the cylinders will stay round.

 

I think I understand the reasoning, if it's true, then it is similar to what what a blacksmith does to temper and harden metal. During it's life, all an engine block knows is "heat--->cool---heat--->cool---repeat"

 

No info on Ferrari's, but the BMW engine situation rings a bell. Not sure where I read it. Roundel??

 

I cannot say whether alloy 'seasons' the same way cast iron does, but I've heard from auto machinists that a rebuild of cast iron is widely considered a 'better' motor.
I wonder if there is a metallurgist on the board?

 

Yes!

I have heard this statement about aging steel and cast iron, from the older and experienced men who mentored me. It seems that shapes and clearances are stabilized, so greater accuracy is possible in machining and fabrication, and durability is the benefit. If this is caused by the unstressed hot-cold cycles, I don't know. But someone out there does.

I've read this about the BMW Turbo 4, where the engineers searched the local wrecking yards, in Germany, looking for high mileage blocks, to have M Power builds for F1. I read they were getting in excess of 1400+ horsepower, for their qualifying engines, before they blew or wore out! Quite an acclompishment!

I've heard this too among INDY Cars when Stock Block Pushrod engines were allowed for a while. Can't remember the Team or Driver, but they said that they found their SBC Chevy, in an old school bus, in the wrecking yard. That may be fiction though, as scool busses would have used BBC Chevy's as truck engines, rather than SBC's.

Also Harley-Davidson, before it's regeneration, used to age the cylinder barrels for their Glides and Sportsters, outside for a year or so to achieve the desired aging, that they required for their Motors.

How this works on Aluminum Alloys and engines with pressed-in steel liners, etc., I do not know. How the Military and Aircraft Industries, use this practice, would be interesting to find out.

Ciao...Paolo

 

I was a metallurgist long ago. When a block is cast it ends up with internal stresses as a result of uneven cooling. Machining upsets the balance of internal stresses, which causes the block to change shape over time as the stresses try to rebalance. A series of heat/cool cycles allows the stresses to be relieved. In theory it applies to any metal, but I don’t know if it is as significant with aluminum as it is with cast iron.

 

this is only true with American engines. They don't let the blocks sit in a field for 10 years like for example Germans do. I have herd many times, by the time a viper is in the junk yard, the engine is just stabilizing. 1 more reason why American cars right out suck.

 

63k and going strong

 

Do you actually believe what you wrote?

 

My Dad knew a guy that built Offy's back in the early 50's. The guy had a bunch of bare blocks sitting outside rusting up. Said it made them stronger. I dont know about that, but I have learned that all metals do work harden over time, but its a two edged sword. If they become to brittle they can crack easier.

 

interesting...ductile iron sleeves are FCC or face-centered-cubic crystalline structure so it'll have a propensity to slip-plane in plastic deformation whereas the body-centered-cubic is much less so and can shatter.

however plastic deformation is not occurring in the cycles of the engine, this is more readily seen in cold-working metal and softer metals like copper and brass.

as to the block casting..great info and a good read for ME's
http://www.ironcasting.org/Gray%20Iron%20-%20A%20Unique%20Material.htm

the addition of graphite or carbon to the block use isn't possible as the combustion chamber is regulated to the head and piston, very little of the sleeve is exposed to it at once. the heat cycle is possible i guess but no where near the temps needed for stress relief, usually 1100*F it can be done over much longer periods of time at temps around 900*F. maybe the 100k cycle is possible.

 

here you go, proof of low temp heat cycle hardens and strengthens iron. with increased machinability.

http://www.eere.energy.gov/industry/metalcasting/pdfs/age_strengthening.pdf