Mainly in making left hand sweeper turns, the oil pressure drops nearly to zero and the oil light comes on. The oil level is topped up ( and a bit over ). I know this is somewhat common, but what can I do to stop this before I do some real damage? I have a tuna can that I can install, but I need something short of splitting the case.

A "tuna can" would be your next step. Also, make sure the wiring is in good shape on your pressure sender so you aren't getting false positives.

If this occurs rarely during street driving, then go with the tuna can and almost an extra full quart.

If this is on the racetrack, then an accusump is the standard solution.

If the heads have crankcase vents get rid of them. That quart of oil that each head holds will drain quickly back to the crankcase instead of trying to puke out the head vents at high revs.

Try it.

And there are some who modify the baffles of the windage tray in the case to allow more oil to get back into the case quicker.
I have heard some just remove it all together.

On a race car an accusump is best.

you can also run a double sump. it hangs low, but it is cheap and easy to install. I ran one for years on my car for track and autocross. I drive my car all summer everyday on 205-50-15/225-50-15 with about 5" under the rocker for ground clearance. I had to be careful, but I never hit it on anything.

Kelly

I made this mod, but I'm dry sumped now...

I run a double sump. 1.5 qt. by Scat for a total of 5 qts. Engine oil temp runs cooler too. Just have to take it slow over speed bumps. Have not scraped anything yet running 205/60/15 tires.

This is just an aggressive "around town" car.

On my old 4 cylinder race car we fixed the starvation with just the 'tuna can' sump plate plus running it about a quart over full. This was a full race E-Production car on race tires and survived turn 17 at Sebring so that solution should do your mountain roads just fine ;-). It might cause some smoking on the street, so maybe you could try starting out half a quart over and see if it's good enough.

I installed a tuna can and I never had the light come on in turn 17 either. And that was on some pretty hot days.