Oil Drain Back?

[peterman]

Hey Guys,
I just replaced my head with a new one that I built up with a Bimmerheads 272 billet cam and all new internals - Everything, including valve guides.
When I start the car the oil light stays on for anywhere from 1-4 seconds, only on cold starts.
I did not have this problem before. The oil light would turn off almost immediately with my old head on.
I did replace the crank bolt seal and the intermediate shaft seal while changing the head out. I have no signs of leaks on the bottom end.
I have a small weep from the valve cover gasket.
Any ideas what would cause the low oil pressure at cold start?

I do have a gauge on it which reflects what the idiot light on the dash is telling me... Low pressure for 1-4 seconds then 40-50 psi (cold)
It settles down around 10 psi (at idle) when the oil warms to about 140-160F (I have an oil temp gauge, too)

I'm running conventional 20W50.

Thanks,
Pete

[digger]

Only thing that springs to mind is the rocket shaft might be installed wrong? Not sure how that would cause these issues though

[peterman]

Somebody on BF.com suggested that I had a faulty oil filter with a bad drain back valve. Apparently some people have had that as a problem in the past.
I'm going to switch out the oil filter and hopefully it goes away.

[TobyB]

You didn't take the pump off, did you?

Even a tiny leak down there will do what you describe, as it lets air leak back into the system.

t

[digger]

If you changed the filter it's possible I only use genuine filters since I know people have used cheap aftermarket ones and had issue

[peterman]

Toby - I did not take the pump off. bottom end stayed closed up.
I did change the filter again to a Mann filter and the problem remains.
I was talking about it at the track this weekend with my instructor and we had the same thought that it could be the bearing tolerances in the Bimmerheads cam or head bearings... I don't remember the exact spec, but I believe the cam tolerances are within a few tenths. so either warn journals in the head, or a slightly undersized cam would cause the same issue.
Cold start up takes about 3 seconds then stays steady at 60 psi (this AM anyway) If i get it warm (180-ish) then let it sit for about 30 mins, it will take about 5 seconds then settles in around 12-15psi. Consistent with a warn cam journal/undersized cam situation given the oil is now thinner.
The hypothesis is good if the oil pump is doing a very good job given the high (when warm) idle oil pressure with effectively larger tolerances in the head.