high mileage motors and rebuilding

[chiboy002]

so I read a while back, i think in some old articles about engine building, that rebuilding a high mileage motor is actually ideal because of the heat cycling of the block which results in a prolonged stress relief??!?!?!?!?!?!:confused:

something along those lines.

Now, upon my research, as it is time to rebuild my motor which has 25Xk on it, most people opt to build low mileage motors for high performance set ups.

Aside from having stress fractures or warped components, what exactly is the reasoning for choosing a low mileage motor vs a high mileage, if you are making it a bare block and starting from scratch either way?

Thanks

[Croustibat]

People who rebuild old blocks just don't want to spend the money on a new block. Everything else is BS.

[chiboy002]

but what is the point of rebuilding a newer block versus an older one, if the older one doesn't have anything wrong?

isn't it the same thing after all the machine work is done?

[Kingtal0n]

so I read a while back, i think in some old articles about engine building, that rebuilding a high mileage motor is actually ideal because of the heat cycling of the block which results in a prolonged stress relief??!?!?!?!?!?!:confused:

something along those lines.

Now, upon my research, as it is time to rebuild my motor which has 25Xk on it, most people opt to build low mileage motors for high performance set ups.

Aside from having stress fractures or warped components, what exactly is the reasoning for choosing a low mileage motor vs a high mileage, if you are making it a bare block and starting from scratch either way?

Thanks

You are thinking of "seasoning the block" which mainly applies to iron block V8's made between 1965-1988. The mostly aluminum blocks from Honda and Nissan and others do not benefit from "seasoning".

The old iron blocks, after thousands of heat cycles and miles, their insides would shift slightly and "settle down" to some final relaxed state. If you build one with expensive parts and did a bunch of expensive machine work to it, it would be best to use a block that had already "settled down". This was only a problem for old engines, before the technology for creating an engine block improved significantly. When I am going to rebuild an all-aluminum sr20det, I will take the lowest mileage block I can find, because there is less chance that it has been abused/overheated.

About rebuilds,
I am all for an OEM rebuild using the OEM stamped marks on the block, and take it one step further with the dial bore gauge and micrometers if you have them to really dial the clearances in for a long-life OEM engine.

That said, it is fairly pointless to build an sr20det with any expensive parts these days. The parts and machinework just to get you from a 350horsepower engine (stock 150,000 miles capability) to a 500 horsepower engine (forged components) will cost more than simply installing a 2jz/lsx engine, which will overall give you better performance (due to displacement) for less dollars.

[Croustibat]

but what is the point of rebuilding a newer block versus an older one, if the older one doesn't have anything wrong?

isn't it the same thing after all the machine work is done?

The problem is making sure an engine block does not have anything wrong. If you know a perfect way, i am all ears.

An older block has more chances of having troubles, cracks, worn threads, slightly warped surfaces, maybe it has already been decked, maybe it has been machined improperly, and so on.

[Arrowking]

The problem is making sure an engine block does not have anything wrong. If you know a perfect way, i am all ears.

An older block has more chances of having troubles, cracks, worn threads, slightly warped surfaces, maybe it has already been decked, maybe it has been machined improperly, and so on.

Isn't X-raying a block a pretty good way of checking it for imperfections?

[Croustibat]

Xray is a good TOOL, but like all tools, it needs a qualified operator.

My sister, as pretty as she is, can't use tools, even quality ones. She changed her spark plugs once. I told her "remove spark plug, note the wire order, clean the threads, put new spark plugs with your hands, tighten all the way then use the torque wrench". She knew better, or did not want to dirty her hands, so she used the torque wrench right from the beginning. the wrench clicked nearly at the start, but that did not bother her; she just set it on a higher setting, and repeated until she could not turn the wrench.

In the end, she destroyed all four threads on the head.

What i mean is X-ray is a good tool, but it needs a good operator; and even a good operator can make mistakes. It just happens, we are humans. that and problems do not get lit up with a red arrow blinking on them. It does ont detect warping or bad threads too.

[Arrowking]

Xray is a good TOOL, but like all tools, it needs a qualified operator.

My sister, as pretty as she is, can't use tools, even quality ones. She changed her spark plugs once. I told her "remove spark plug, note the wire order, clean the threads, put new spark plugs with your hands, tighten all the way then use the torque wrench". She knew better, or did not want to dirty her hands, so she used the torque wrench right from the beginning. the wrench clicked nearly at the start, but that did not bother her; she just set it on a higher setting, and repeated until she could not turn the wrench.

In the end, she destroyed all four threads on the head.

What i mean is X-ray is a good tool, but it needs a good operator; and even a good operator can make mistakes. It just happens, we are humans. that and problems do not get lit up with a red arrow blinking on them. It does ont detect warping or bad threads too.

Warping is pretty easy to detect for a good machinist. Bad threads can usually be spotted and detected.

And sure, all tools require a competent operator. I see what you're saying but a good machinist with good tools at his disposal can find the faults in a block (if it has any).

[chiboy002]

You are thinking of "seasoning the block" which mainly applies to iron block V8's made between 1965-1988. The mostly aluminum blocks from Honda and Nissan and others do not benefit from "seasoning".

The old iron blocks, after thousands of heat cycles and miles, their insides would shift slightly and "settle down" to some final relaxed state. If you build one with expensive parts and did a bunch of expensive machine work to it, it would be best to use a block that had already "settled down". This was only a problem for old engines, before the technology for creating an engine block improved significantly. When I am going to rebuild an all-aluminum sr20det, I will take the lowest mileage block I can find, because there is less chance that it has been abused/overheated.

About rebuilds,
I am all for an OEM rebuild using the OEM stamped marks on the block, and take it one step further with the dial bore gauge and micrometers if you have them to really dial the clearances in for a long-life OEM engine.

That said, it is fairly pointless to build an sr20det with any expensive parts these days. The parts and machinework just to get you from a 350horsepower engine (stock 150,000 miles capability) to a 500 horsepower engine (forged components) will cost more than simply installing a 2jz/lsx engine, which will overall give you better performance (due to displacement) for less dollars.
ahhh okay, yeah thats exactly what I had read about it and could never find the damn info again! Thanks Kingtal0n

I'm actually rebuilding my KA so it has an iron block, which means the seasoning stuff applies to my block vs picking up another low mileage one.
Thanks again man
The problem is making sure an engine block does not have anything wrong. If you know a perfect way, i am all ears.

An older block has more chances of having troubles, cracks, worn threads, slightly warped surfaces, maybe it has already been decked, maybe it has been machined improperly, and so on.
Well, the engine in question is mine and the oil pump failed. The motor still runs, compression is there, but I have plans for the motor that I would rather see happen with a rebuilt motor rather than a potentially tired motor.

I do plan on having it all checked out though, I'm just one of those "likes to keep original items together" people and don't like the idea of putting a new motor in my car. Superstitions and stupid preferences, but it helps me sleep at night...

Isn't X-raying a block a pretty good way of checking it for imperfections?
yeah I was thinking of going magnaflux, I'm hoping everything checks out cause man I don't want to find another block with unknown history

[chiboy002]

for those interested in reading up on seasoned blocks

http://www.f1technical.net/forum/viewtopic.php?p=46870

https://www.google.com/search?q=seasoning+a+block&rlz=1C1AFAB_enUS496US496&oq=seasoning+a+block&aqs=chrome..69i57j0l5.3097j0j7&sourceid=chrome&es_sm=122&ie=UTF-8#safe=off&q=seasoning%20a%20engine%20block

[Croustibat]

TBH this seasoning feels like a load of bull.

Until i get some real maths behind that, i'll consider the guys who wrote that:


the old myth about seasoned blocks came about when the foundry could make more blocks than the machine shop could finish given the quality of the machining process and tooling back in the 50's, 60's and 70's. So, the foundry had to store the blocks for machining and they would sit them outside since they knew the machining would remove any rusted areas in critical areas and vating before maching or before assembly removed the remaining rust. Old wives' tales were born from seeing all these blocks just sitting outside in the snow or summer heat in Michigan or where ever they foundry was located.


is right.

[jza80king]

I rebuilt my Ka24de after 250k miles back last year. One of the ways they checked the condition at my machine shop was with a dye penetrant. This will allow you to get a better idea if a particular surface is not completely flat or cracked or warped etc. Depending on certain surfaces, it can be machined or milled slightly and if the motor is re-assembled correctly with quality parts/gaskets etc it shouldn't matter if the block had 250k miles or 25k miles. I think the thought behind rebuilding something with less miles is a little overblown. My example to you would be, let's say I had 2 of the same motors to sell you for a rebuild you are going to do. One has 200k miles but the oil intervals were religiously done and quality oil and filters were used every time. The other motor only has 50k miles but in many occasions the oil intervals were done 5000 miles late and valuecraft oil and a shit filter was used every time. Yeah the 2nd motor has been used 150k miles less but which would you wanna buy to rebuild?

[Kingtal0n]

Great discussion, great questions raised, just to add to this discussion,

Imagine you have an engine with 10,000 miles on it. Take it apart, measure everything, then put it back together and run it to 200,000 miles and take it apart again.

We should not be surprised to find bearing wear, camshaft wear, piston ring wear.
however, what about the cylinder roundness and deck flatness? These things should not have changed... however, if the block was produced in the 1980's, I would not be surprised to find that the cylinders are no longer round.

So then, you take it apart, re-bore the cylinder block .030 over, and re-measure everything else to make sure the other important things didn't move (the alignment of the crankshaft journal with the center of the bore, for instance). the hope is, since the cylinder already distored due to 200,000 miles of heat cycling and use, and was re-bored, it should no longer have the propensity to distort any further (presumably, the block has been "seasoned" by 200,000 miles of driving and will experience no further distortion).

And I agree, these days, it is automatically a better choice to go for the cleaner engine, the one more well maintained, regardless of mileage.