I would start out wth straight 30 weight.If the oil pressure goes below 15 psi when hot go to straight 40 weight.I used to run 20/50 in everything,and I found out from experiance that I had just as much oil pressure with thinner oil and get better oil flow and less bypass around the fiter.Years ago I ran 10/30 weight cheap oil in the 7500 rpm smallblock in my firebird because I worked at a shop where that oil was free out of the overhead pump.Never had a problem with it,I pulled it apart after melting a few pistons with crazy nitrous and the bearings were perfect.Don't fall into the "special racing oil" trap.If you need Zinc for flat tappet cam buy the additive,and use regular oil.

 

Brad Penn 10-w30. for flattappets.

lots of zinc.

 

brad penn 10-w30. For flattappets.

Lots of zinc.

x2

 

I don't like the straight weight oils like 30w because of how it changes with temp.
A lot of dragsters use 20w50 in their motors which is pretty thick, but they only do things a 1/4 mile at a time.
If your going to be driving around, 10w30 is a good all around weight, valvoline, mobil 1, royal purple are all good performance oils.

 

The correct weight oil depends a lot on bearing clearances. You want to run as thin an oil as possible that will give you the necessary oil pressures throughout your operating range. Thinner oil ceates less drag on parts and can release a little more torque and HP. An engine with very small rod and main clearances (1-1/2 to 2 thou) may effectively run 5W30 and be fine. If your engine has 2-1/2 thou on rods and mains you would probably get best results with 10w30, perhaps 10w40. I'm running 2-1/2 thou rods and 3 thou mains and use 15w40 GTX Diesel oil. I have 20-30 psi @ idle (1000 rpm) and 65-75 psi @ 5000 + with engine @ 180 temp (355 small block).

Keith

 

The correct weight oil depends a lot on bearing clearances. You want to run as thin an oil as possible that will give you the necessary oil pressures throughout your operating range. Thinner oil ceates less drag on parts and can release a little more torque and HP. An engine with very small rod and main clearances (1-1/2 to 2 thou) may effectively run 5W30 and be fine. If your engine has 2-1/2 thou on rods and mains you would probably get best results with 10w30, perhaps 10w40. I'm running 2-1/2 thou rods and 3 thou mains and use 15w40 GTX Diesel oil. I have 20-30 psi @ idle (1000 rpm) and 65-75 psi @ 5000 + with engine @ 180 temp (355 small block).

Keith

Exactly, there is no 1 magic oil that is good for all performance engines.

 

I also like Delo 400 10-40.

Ran it only in my 355 and was always looked good when changed.

I did run a hyd roller cam though.

 

I blew an oil filter apart once on a new HP VW air cooled motor with full-flow filter system using 20W50. I have always used 10W40 after that.
On a new old style V8 like most talk about on this forum I wouldn't use anything other than 10W40. Remember that the 15W40's are a high detergent oil intended for diesel engines and for gasoline engines should only be used on a new clean engine (after proper break-in). Personally I wouldn't use that high a viscosity myself on a gas engine anyhow. Diesel engines are built with larger clearances and need the higher viscosity.
Newer performance engines (not custom engines) need 5W30 and some use 5W20. Part of that is reduced friction for better performance and economy. But another reason for the thinner oils is reduced clearances. A 20W50 would probably cause some of these engines to starve and burn up if they weren't worn in real good.
No I don't build race engines or know anyone that does.
Yes I am a diesel mechanic but I do have a degree as an automotive tech also. And I have gray hair.

Jeff

 

A somewhat parallel conversation going on here.

 

I run valvoline VR1 in 10w30. I typically have 8-10 psi at a 700 rpm idle. By 1,000 rpm it has about 17-20 psi. The important thing is that you have good oil flow. As others have mentioned, a quality additive like ZDDPlus is cheap insurance if your running a flat tappet cam.

 

I'm a big fan of shell rotella 15/40 for the older cars, lots of zinc. (esp if you have a flat tappet) I even run it on the 68 with the roller motor.

 

This is my oil too. Love rotella use it in both performance cars.

Thinking of switching to royal purple though. Just hit the 400 mark on the 383. Use 10w30.

Use straight 50 weight in my Trans Am. It has tighter clearances but the oil will make it in, the only reason I am doing it is because I run a T-Trim which is fed from my oil pump. Thinkin of going synthetic too.

 

Ask the engine builder !

Im most everything we run Royal Purple race oils, Valvoline VR1 in everything else

Red Line oils are good too, I hear Lucas is too

 

I like the synthetic rotellas...