ArKay99

iTrader: (1)

This is something I didn't expect, nor can I explain. I'm hoping someone can give me a valid reason for this. Last year I put a set of AFR heads and a cam in my 99 C5 bolt-on LS1. I also installed a new ported oil pump, new Comp 850 lifters, and Harland Sharp rockers. The swap went well and has run well since. The only issue I had was the car lost approx. 5lbs of oil pressure across the board. Instead of hot idle @35lbs. it was 30lbs. at 4000rpm's it was 60lbs. where it used to be 65lbs. No problem though, it was well within spec. I recently redegreed my cam and when I had the cover off I shimmed the bypass spring .060" and got back ~3lbs. overall. I just recently had my old rockers upgraded at Harland Sharp and swapped them yesterday along with shimming the springs another .060". When I started the car I looked at my cold idle and it was almost 50lbs. I let it idle until warm and started to drive it. The oil temp went to 200 degrees and when it went to idle it was almost 40lbs. when it would be about 33lbs. The only thing I changed was the spring shim thickness, and the rockers. This is one time an unexpected change has had a positive result. Any ideas?

99ssleeper

iTrader: (98)

something to do with lifter preload I'd say...

y2khawk

iTrader: (5)

They (HS) may have reduced the oiling hole in the rocker for the shaft bearings.

joshZ28

With a ported oil pump, you will have less velocity and more volume. That will cause your oil pressure to drop. I'd say shimming the spring that last .060" had more of an effect on the oil pressure than the rockers did. Try removing the last .060" and adding, say .010" at a time and see what happens. It may take a while, but oil is the blood of the engine.

ArKay99

iTrader: (1)

I understand the ported pump will have more volume and less velocity, but not that much. What I may not have communicated clearly was I changed the shims under my valve springs yesterday, not the shim in the pump. Also, I was running with the shim in the pump for 2 months before I changed the rockers. I was well aware of the oil pressure differences before this. I was contemplating shimming the pump another .060" and calling it a day, but changing the rockers gave me back my oil pressure and a little more. I think Harlan may be correct. Different size oil holes in the rockers. I'm gonna be pulling the valve covers off to switch them in a few weeks and I can compare the oil holes to the Harland Sharps then. Also, btw I was using 7.350 pushrods with the Harland Sharps and had 7.4's in for a while. The oil pressure didn't change with either so I don't think it is preload.

Full-Force

iTrader: (11)

It just better oil control that the rockers have. You are probably getting less sling with the HS rcokers and more pressure oiling.