SeVa-S13 wrote:Just fyi, 139k isn't that much for a Nissan...
True. Mine's at 210000 miles and I'm in no real rush to rebuild or replace the motor. I just pay better attention to it than I think I normally would. LOL... I've gotten REALLY good at pulling codes from the ECU.
Save for a while. You have more options than you think. If your block and head are sound, you can rebuild the engine with higher-performance pieces to eek out some N/A gain or prep for boost. Or, if you want to keep it stockish, use OEM parts. From what I've found, a rebuild, if possible, can be a better option than remanu or used engines. However, if there is the slightest problem with the engine components, you should probably look at a full swap. Needless to say, this really shouldn't be a problem for you for at least another 50000 miles, IMHO.
Quick question... I've heard of porting the head for performance gains, and only on forced induction engines or BIG N/A engines. Is that what you're going for? Or is this an attempt to increase engine longevity?