how to 'fix' aging?

[t2000gts]

what exactly happens when a motor is worn out? like say a stock 2ZZ-GE at 200-250k miles...how would you go about rebuilding it so it's "new" or making as much reliable power as "new"?

also, is it the same for when you wear out a motor with too much power? if i sprayed nitrous often, and the car got progressively worse, is that like an accelerated aging thing?

[scapamouche]

With the Chevy V8 crowd, an engine rebuild is in the cards at that point:

Complete disassembly, and cleaning of the heads, block, crank and rods.

Bore out the cylinders to restore the finish (maybe 10-20 thousandths of an inch) and polished.

magnaflux the rods and crank, looking for cracks. If present, replace, if not, then shot peen the rods and polish to releives stresses, similar treatment for the crank.

Get new pistons and rings for the new, larger bore; assemble the rotating mass and get it balanced.

New cam, new oil pump, lifters, new valves and valvesprings, valve job on the heads, new rocker arms if needed, clean up the intake, recondition the distributor and carb 9if there is one)

The list goes on. The basic idea is to rebuild the engine till effectively new. As an FYI, in many cases, a used block is more desirable for the Chevy crowd because its well seasoned: any bore drift has happened, everything is wron in nicely, etc.

[V8Celica]

With the 2zz-GE there is one major problem to overcome when rebuilding the engine. The cylinder walls are coated witha special compound from toyota. Overboaring the cylinders to restore trueness will take that coating off. Re-crosshatching may also remove that coating. As of yet, I haven't heard of toyota selling the coating in any form. That could change though.

[marcus_GTS]

Yes, the 2zz-GE's cylinders are coated with a hard ceramic material to reduce wear. If you ever do need to re-bore the cylinders, you should have this coating re-applied. I have heard that the stuff they use is Nikasil, which has been used for a long time in motorcycle engines. That would make sense since Yamaha assembles the engines. If that is the case, then you might find a motorcycle engine rebuilder who could do this.

[t2000gts]

hm, how about if i bought new pistons, rods, etc.? then it would basically come down to boring the cylinders and shot peening the crank?

and a completely new valvetrain.

hm, maybe it would be easier at that point to buy a low mileage used 2ZZ-GE and work on that, and swap that into the car.

[marcus_GTS]

As has been stated, boring out the cylinders would remove the ceramic coating. Your new pistons would be rubbing directly against the aluminum cylinder, and you'd likely be burning major oil within a few thousand miles, and the engine probably wouldn't last more than 5000-6000 miles before the piston slap was unbearable. Buying a used, low-mileage 2zz-GE is probably the most cost-effective method. You could also buy a brand new block, but that is really expensive.

[t2000gts]

how much is a new block and/or head compared to a new engine or a low mileage engine?

[inline4]

a lot

[inline4]

I'd rather just get a new car at 250k..

[chameleon]

Just out of curiosity, since the cylindars are coated in this extremely tough material, isn't it possable that they will not require any resurfaceing during an engine rebuild?

[V8Celica]

It's not a matter of having scratched up cylidar walls, but rather getting the new piston rings to seal properly against them. When you resurface the walls, you put a cross hatch patter on them. The cross hatch acts as a file, fixing any inconsistancies between the rings and the walls. Without the cross hatch, the rings will not seat properly resulting in a loss of compression. I don't know how the coating affects this. You could ask a motorcycle engine rebuild shop to know for certain.