3mm doesn't sound near enough clearance, however I'm also not a fluid dynamics person, so that may not mean much. I'm going to do a fresh oil change with 20w50 brad penn as I have a bunch of it sitting here. Then I'll do the free rev test and report back today/tomorrow. Thanks.

 

OK, so I was wrong in having oil on the shelf and had to get some in from Summit. So to recap, I just did a fresh oil change with Brad Penn 20w-50.
I took some video clips to show oil pressure at idle and during cold and warmed up revs. Links are below but the rundown is this:

- Cold startup @63F degrees was upper mid to upper 90s psi at around 1500-1600rpm (while warming up). Couple short throttle blips while cold netted around 106-107psi @3,500-4k rpm.
video link:
- 117F degree engine temp sat around 85psi oil pressure @about 1,300rpm and with some throttle blips around 110-111psi @5,500-6k rpm.
video link:
- After around 15min and water up to temp I did some free revs and held it a little bit. I didn't want to just hold a free rev for a long period. Idle oil psi @ around 1,200rpm was 48psi. When revving up it got to about 100psi at 6k rpm and then fell off as I got a little higher (7k+) to about 95-96psi. Didn't seem to drop from there but I didn't leave it up there too long.
video link:
- After about 20min the engine had gone through several coolant heat cycles and the oil temp was up. Idle was around 1100 and the oil psi was 37psi. The idle needs to be lowered a little bit on this map, but I know with Brad Penn 15w-40 my oil pressure is 25-27 @1k idle rpm. So, I'm sure if I drove the car and got the oil hotter then it would probably be close to that.

**Oil temp on my dash is not yet setup, so it's not correct**

Maybe this shows that it is an oil pickup issue under acceleration? Not sure...

I am not familiar and haven't found any hard data to what the OEM spring piston bypass psi is on the OFH. I'm sure this could be affected by weight of oil. Is there a know pressure to which this piston "opens"?? Is the weight/pressure of the oil/pump forcing this piston to open more/longer than it should and not maintaining pressure at higher rpms?? I was thinking about machining a small spacer to go under the pressure spring to see if it helps the upper rpm drop. Has anyone heard of this being done? Thanks!

 

All looks about the same as my built motor.

 

@Jonno99 thanks for the feedback.

 

There is no requirement to shim the oil pressure regulator spring.
The regulator will be doing it's job. The pressure at the regulator will likely be constant.

The oil pressure drop at higher rpm will be two things.
Either the oil pump efficiency is dropping off very fast (cold oil doesn't help), or there is additional "leakage" at higher engine RPM's.
Additional leakage at higher RPM is completely normal. Bearings and camshaft oiling requirement raise with rpm.

This drop from 102psi to 95psi, is this what you were seeing on the road also?
Or was the drop more on the road?

 

The pressure drop is greater on the road. Gets down to low 70s if I rev it to 8500-8800rpm in 3rd gear for example. It’s not a a sharp drop off, just slowly decreases as you get passed 7k rpm, decreasing almost linearly as rpm increases.

I have not tried over filling the oil slightly but perhaps this is worth a shot as well. Maybe will show it’s an oil slosh issue?

 

Overfilling is an excellent way to confirm if it's oil surge, or if you have another problem.
Add a quart/litre extra oil and try again

 

OK, So I filled about a half quart over with 20w-50 and took the car to work this morning. Recorded a 3rd gear pull but didn't go over 8k and you can see that starting around 6.5k the pressure starts to drop off from about 99psi to 84psi by the time it gets to 7.5k.

The confusing thing for me is that the pressure is great (higher than it prob needs to be) at anything below 6.5 and doesn't taper off till higher rpms. If you go based on the 10psi per 1k rpm rule that is...

Looking at my last logs I took before this oil change on the 15w-40, it seems that I'm about 8-10psi higher above 6.5krpm than I was on my last log pulls. Below that though, it is very similar (within 2psi) till around 4-4.5k. In this 4-4.5k range both weight oils are about 99-100psi (fully heated up) peak and don't really increase from this point. Then both oils started falling off at the same point (6.5k) but the 15w-40 fell off to about 74psi at 7.5k rpm and the 20w-50 fell to 84psi at 7.5k.

So in a nutshell. The overfilled oil did not seem to stop the drop itself at higher rpm and MAY have had an impact on the psi staying about 10psi higher on the top end (or it was the thicker oil).