Triumph Repair: oil pressure, pressure release valve, hydraulic gauge

Question
I just got done doing the head over in my Tr6. I also installed  roller rockers, a mild cam and headers. It's an orig engine with 93K on  it and always had great oil pressure. It ran at 75-80 lbs cold and 50lbs hot. After the rebuild it still runs at 75-80 cold but is now at about 25-30 lbs hot. I changed the sending unit but no change.

The only thing I did different was after breaking in the cam I drained the 15-40 oil and used GTX 10-40.

I usually run 10-40 in the spring and change to 20-50 in the summer.   any ideas why the change in pressure????

Is 25lbs safe?  any help would be appreciated


Answer
Hi Mark,
If you had used 10-40 before and didn't have a pressure problem and all you changed was the cam and lifters you should still have the same pressure. Did you mike the cam journals of the new cam and compare it to the old cam journals? This is the only place you could lose oil pressure if you have not disturbed the mains, rods, oil pump or pressure release valve. The only other place is the rocker arm shaft. To check this all you need to do is remove the valve cover and start the engine. You will get some oil on the manifold so you can tape a piece of cardboard around the head. You should see some oil but it should not be excessive.
I would suggest you get a hydraulic gauge to test your pressure as an electric gauge and sending unit are always suspect in a shop. Even if the sending unit was just replaced.
25 to 30 PSI is ok on some old domestic cars but not good on any British car I have worked on. I use 10-40 on MGs, Triumphs and Jags with no problems with pressure.
25 to 30 PSI is OK for an idle pressure but not running at cruise speed.
let me know,
Howard