The RB26 is a timing belt engine. Like any engine, you want to make sure you get all the pulleys lined up correctly for the engine to run right. If you don't get everything lined up, you can end up chasing issues, that turn out to be an actual mechanical problem. It is a little difficult to get all the dots and marks lined up because most of the time you don't have a straight view. Since your view is a little off, it helps to use a straight edge to double check all the timing marks.
My personal experience is that every time you have to go into the front of the RB26 engine, you want to replace the water pump, you want to replace the idler and tensioner pulleys, and the belt. You don't have to, some people get away with it, but for me, about every time I haven't replaced one of the big pulleys (bearings) they make noise. Kind of a "woooo,woooo,woooo" noise. Then the water pump I didn't replace, starts leaking out of the weep hole. Eric over at EPP stocks a ton of RB26 parts, and I just picked up what I need to do the front of the RB on NISMO #500.
RB26DETT Cam Timing Adjustment
RB26DETT Ignition Timing Adjustment
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