What grade oil are you running, 10w30 etc?

On a high volume oil pump you can see anywhere from 75-90 psi @ the upper rpm range.

The only other possibility I can think of other than tight bearing clearances would be the timing chain dampener which has a bleed off hole that lubes the chain by squirting oil out onto the lower portion of the chain.

This bleed off hole also prevents over tensioning of the timing chain which will wear down the plastic wear pad prematurely.

The dampener is not a tensioner, it's just controls (dampens) the slack side of the chain.

If you used an RTV silicone sealant when you installed the chain dampener and blocked up the oil feed to the dampener with the RTV then that would cause a rise in the oil pressure, but there would be some chain noise because the chain wouldn't be dampened properly.

Chucky MoMo <img src="/forums/images/graemlins/wink.gif" alt="" />