Oil pressure at idle

I drove around today for the first time more than around the neighborhood. I got the transmission leak fixed (so far) with some rtv and a new tower gasket. My engine has new rings and bearings and is getting about 40psi at 40-45 mph and about 30 at 30-35. However, after it's good and warmed up when I'm stopped and at idle the pressure drops to about 5-7. It's scaring me to even drive it. The gauge is new. What should I do?

Yeah it's scaring me. So 40 for 40 and 30 for 30 is about normal though? About what rpm do these things idle at if normal?

Edited by wrdabney - 25 Apr. 2012 at 2:25am

So could it just be that I have it idled too low?

What brand and weight oil are you using?

I'm using auto zone brand conventional hd 30.  I didn't know you were supposed to run something specific for break in period. what is recommended?

There are three camshaft bearings in these engines, and only one of them has an insert we can replace. There's bound to be some wear in the other two. This is a prime place for oil pressure to be lost. There's almost nothing we can do but live with it. And, main and rod bearings are made to have more clearance nowadays than before. With the crank ground to spec and new inserts, bearing clearance will be on the large side, near the limit. Again, very little we can do about it. Think about this -- the pistons are small (light) the rods are spindly, (light) and the compression ratio is low. How much oil pressure is really needed? Chevrolet said that even in a 350 with 11:1 compression, 10# per 1000 RPMs is enough. A lot of engines built at the same time as our little L134 did not even have full pressure oiling systems. The rod bearings and sometimes the mains as well were oiled by dippers on the rods.
This is one of the reasons why all the manufacturers replaced the guages with "idiot" lights ( the oil light does not come on until pressure drops below 4#) or took the numbers off the guages and replaced them with "Low, Normal, and High".   Sorry, I got carried away.   BW

wrdabney wrote: I'm using auto zone brand conventional hd 30.  I didn't know you were supposed to run something specific for break in period. what is recommended?

wrdabney wrote: ... However, after it's good and warmed up when I'm stopped and at idle the pressure drops to about 5-7 ...

Yup .020, you can pull the front cover, unscrew the nozzle weld up the hoel and re-drill it pretty easy.  Some guys go the other way and plug the line to the oil filter to test the oil pressure.  Use a 1/4 inch pipe plug in the block where the line goes to the oil filter.  don't worry about oil to the gear, it will get enough from the squirter.  That will push extra oil to your front bearing and may jump your pressure up a bit.

Edited by Gunslinger - 26 Apr. 2012 at 11:13pm