I replaced the head gasket this last weekend.
It was starting to leak coolant. Not bad for 170k miles though! While i had the head off, i decided to get the dremel out and clean up the areas around the the valves. As many of you know, the 4g15 chambers have lots of ridges and projections around the valves. These are a major impediment to air flow through the head. I only had one day off work to do the job, so i didnt get into pocket porting around the valve stems and ports,as these are the other area that needs attending to on the 4g15. I am thoroughly impressed with the results of the moderate porting i did however! A noticeable improvement throughout the entire rpm range. Seems to help most low to mid rpm which is where i suffered most due to cam timing. The torque curve is definately flatter! On another note, i also had to change the front main seal which had less than 30k on it! WTF? I popped it out with my fingers! It came from autozone. I have had problems with autozones belts stretching. Hmmm. Or anyone think the unusual wear could be mechanical?
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I really gotta find a 4g37 ECU now though. After the chamber port my idle is crappier than ever! 
