Quote:

I use to run NHRA stock, some of the fastest NHRA SB engine builders and racer said to not use the stock windage tray in the SB, I was dumb enough to not trust them so I did a A,B,A back to back teston a customers 1971 340 on a DTS engine dyno to see if they where right on the stock 340 windage tray It lost HP and torque with the tray in it above 4500 RPM Another freind of mine that has set several NHRA class records did use the one way oil screen on a stock cut out windage tary like on the picture on here, that works



My guess is that 4-bolt caps were being used (?) with the stock tray. At high rpms the bay to bay pumping exchange is limited and that will cost hp.

It gets complicated.

One of Smokey's Nascar 2-bolt main blocks has rounded main caps for that reason. You see that on many modern engines.

Windage trays have diametrically opposed technical requirements which are typically best met with multiple layer trays.