[locomotivebreath]

So that’s the 15w50 sample ? What was your pressures with the 50wt ?

[Verdoro 68]

Originally Posted by locomotivebreath

So that’s the 15w50 sample ? What was your pressures with the 50wt ?

Yes, 15-50. I ran it because that's what Butler recommended. I have a Butler 60 lb pump with a shim and I was seeing the gauge pegged to 80 while cold and while driving. At idle when hot it was 45. My clearances are .020 on the rods and .025-ish on the mains. Normally, I'd be happy with high pressure, but after reading a few threads around here I thought maybe it's unnecessary. I was also wondering if the high pressure was kicking in the filter bypass, but it looks like things were filtering fine.

The 15-40 I put in knocks the pressure down to 75-ish while driving and a little under 40 at idle when hot.

[Schurkey]

Originally Posted by Verdoro 68

Yes, 15-50. I ran it because that's what Butler recommended. I have a Butler 60 lb pump with a shim and I was seeing the gauge pegged to 80 while cold and while driving.

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

Originally Posted by Verdoro 68

The 15-40 I put in knocks the pressure down to 75-ish while driving and a little under 40 at idle when hot.

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

[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.