[locomotivebreath]

Are you using factory rally gauges ? I have repro rally’s and wonder how accurate they are but my psi with Mobil 15w50 seems about the same as yours .

[PAUL K]

I think a lot of engine builders recommend thick oil because it works. Hard to beat experience. I know one career SS racer that tried using thin oil and he had a rod knocking the following race. It may have had nothing to do with the weight of the oil. But if one races for twenty five years using thick oil and never has a bearing failure, then tries light oil and has a problem.... He's going to be hesitant to run thin oil. Butler's used to recommend straight straight 50.

[Verdoro 68]

Originally Posted by Schurkey

For reasons of their own, Butler wants molasses in the oil pan. I think they're nuts.

Next time, try 5W-30. MAYBE 10W-30.

That's in line with Driven's viscosity recommendation based on my clearances.

https://drivenracingoil.com/c-138953...viscosity.html

I started using VR1 20w-50 years and years ago as a crutch for bad bearing clearances and the flat tappet I was running. I just kind of kept with the heavy stuff after the rebuild, especially since Butler recommended it. Seemed like a safe bet but then I started doing some research and thought maybe it's more than I need. There was a recent Engine Masters that tested viscosity that was pretty interesting.

Originally Posted by locomotivebreath

Are you using factory rally gauges ? I have repro rally’s and wonder how accurate they are but my psi with Mobil 15w50 seems about the same as yours .

Yes, factory rally gauges rebuilt and calibrated by Pete Serio so I trust them.