oil pressure and different weight oils

just cranked my 408 last saturday, and man did she run good! well, I let it run up to 160 degrees while I fine tuned the timing, and then I cut her off and let it cool on its on without the fan and pump running. oil pressure was 45 lbs when it fired up cold. once it got to 160 degrees it went to 30 lbs.

I went inside for the night, and got to thinking about the oil pressure later on. I was thinking that it was kinda low. well, I didn't get to mess with it all week because I had my 3 year old while the wife was in florida working. she came backe yesterday and I finally got to play today. heres how things went.

started it cold and had 45lbs oil pressure running at 2,000rpm to warm the motor. at 180 degrees I dropped the rpms down to 900 and the oil pressure went to 13lbs! I shut it off asap and sent into thinking mode. called my stock eliminator buddy who runs a camaro and we discussed it for a moment. he said at idle his camaro runs 20lbs oil pressure when its hot, and that he idles at 1300 rpms. he has won a championship and set 14 national records with that motor so I guess its ok.

we came to a conclusion based off of what has been done to the enigine.

high volume oil pump
oil galley tubed and main passages drilled oversized
main bearings clearanced to .028" for use with 2 step (per engine builder)
rod bearings clearanced to .025" for use with 2 step (per engine builder)
cross over tube to feed the rockers and its passages are a little oversized
running 10w30 oil.

conclusion is that the high volume pump will kill a little due to bigger passages. also have some passages in the motor bigger and that is a little of a pressure killer. biggest thing we think is that the 10w30 is too thin and some of it is leaking between the bearings and journals on the rods and mains, since they are on the loose side clearance wise.

we feel like changing to 20w50 oil will bring the pressure back above 20lbs. I also have to idle the motor at around 1300 to 1500 rpms at idle. he said I'm not racing modified street motors anymore, and I can't idle at 800rpms anymore.

what is the opinion of you guys?