[PontiacLars]

I checked some oil charts and with my clerances, iron block and auto cross or street driving the recommendation was 20w50. Pure drag racing could use lighter as the oil did not get that hot.

My engine is a 4.5" stroker with roller camshaft.

[Jay S]

The flow characteristics change a lot between oil brands, even with the same viscosities, the chemistry is different also, no chart I know of is very accurate for uses of various oils between brands.

Road racing, street and drag engine are all different things, the oil gets darn hot on some drag engines, oil can be over 250*F by the end of the run. Especially filled blocks.

To determine proper oil weight after some usage I usually use the pressure drop after warmed up, or to much pressure warmed up full throttle, cold pressures to high or low, and heat soaked idle pressure. A racing grade 10w30 will take a lot of abuse.

[Jay S]

Originally Posted by PontiacLars

My engine is a 4.5" stroker with roller camshaft.

What lifters? solid roller or a hyd roller?

[PontiacLars]

Originally Posted by Jay S

What lifters? solid roller or a hyd roller?

Johnson hydraulics.

[Jay S]

Originally Posted by PontiacLars

Johnson hydraulics.

There have not been reports of those lifters being very sensitive to oil viscosity. There have been some guys that have said sometimes thicker oil made more power on the dyno with some hydraulic rollers combos.

I attached Driven’s cheat sheet for their oils with different operating temps and oil clearance. Also a chart comparing viscosity in cSt versus temp (*F) between a 5w50 FR50 driven and 20w50 Valvoline VR1. The cSt is on the vertical. Driven FR50 is competition for Valvoline VR1 5w50, I would expect those two oils viscosity to be similar. Not far after about 150*F the 5w50 and 20w50 VR1 the viscosity looks similar.