b18c5 with pct pistons
honda 10w30 oil
stock type r radiator
ebay 4-1 header,60mm mugen cat-back(alot back pressure)
under 20mph - the temp needle on 3/4
over 50mph - normal temp(205f max)
fan ok
oil level ok
coolant ok
no smoke
no milky oil
no oil in radiator
oil pressure is keep droping(20psi now)
oil is leaking between head and block on the distributor side(i think is o-ring)

wonder if head gasket blown or warped head :help:

 

you might try a compression check on the cylinders. If you've got a blown head gasket it can take a while for the coolant or oil to become visibly contaminated. What you're looking for w/a compression test is one (or, more rarely, two ) cylinders w/much lower pressure(s) than the other(s)-

Did you assemble this engine ? What I mean is, did you start with a 'known' good engine and swap out parts or did you pick up an engine block from one place and pieces and parts from others?

oh,duh- I just re-read your post. Is there a thermostat installed on this engine ? Have you tested the thermo to verify it functions as it should?
That would be one of the first things I'd check.

Good luck!

 

how old is your radiator and tstat?