How many miles before rebuild?
 

Okay, so my Evo just turned 90k miles. I have plans for it next Winter to add a set of S1 cams, BBX Full or Lite turbo, ported manifold, and o2 downpipe. Right now my motor seems very strong. Haven't done a compression test, but I think I will this week sometime just to see where I stand. It doesn't make any funny noises or anything like that. In fact I baby the hell out of my car, and drive like a little old lady lol.

Is 90k miles too much to do those types of mods? I don't have a problem spending the extra $3k it would cost to have my entire motor rebuilt, but if I can get another 30-40k safely then I'd rather go that route. When I do the cams I will also be replacing the timing chain, and head gasket.

The only way to truly know is do a leakdown and compression test. Otherwise, you're simply guessing unless your engine is exhibiting symptoms of a larger problem.

Just do a compression check. You could probably get to 150k easily if you change the oil every 3k and don't beat on it. If you don't launch your car, know how to drive manual, and change the fluids early, these Japanese cars last forever even with decent mods. There are the occasional lemons and exceptions, but its mostly how you drive and take care of it.

One guy on here was still fine at 180k evo 9 with 360 whp. I think he did clutch at 70k, but launched and auto crossed his quite a bit. BUT if you don't have a problem shelling out another 3k then you might as well spend another 5k and get your motor built to perfection.

I would make an argument that almost any car, regardless of country of origin, will last a very long time when maintained and cared for properly.
I would be surprised if Evo owners werent getting at least 150K, assuming proper maintenance has been done.