If by saying "free things up a bit" you mean you're looking for more power then you'll have to be open to changing from "old think". Cold start and low temp operating (which means the 15w part of the vis range on your oil) doesn't mean much in race engines, unless you tell me differently I'd guess you're operating in the "max temp" end of the spectrum, so for practical purposes you're running an SAE 50, and just for comparison that's at the heavy end of say an SAE 80w90 gear lube. Odds are you're running 60 or so psi (with a stock style pump)with the skinny pedal down which means you're dumping over the relief all the time (at least at the higher rpms). If you've got a "high pressure" pump, that just means the point at which the force of the oil flow opens the relief is higher, so it will mean more resistence to flow (the definition of pressure in a fluid system) so it would read something around 75 pounds (does absolutely nothing positive for oiling performance, just heats the oil more). Now, this is where folks get all self righteous and say how successful they've been doing yada yada. And I wouldn't doubt most of them, they probably have been successful. But that's more of a testiment to how tolerant most engines are of a wide variety of applications when the measuring stick has a lot of latitude.
Testimonials like that are interesting but of dubious value. One of my life's careers was in field engineering for fuels and lubes, and through that I had the opportunity to hear just about every kind of oil performance testimonial and it's equal/opposite counter testimony. e.g. "Pennzoil sucks I can prove it................Pennzoil is the only one you can count on, I can prove it". These types of statements very often came from folks in similar application situations, with apparently equal success in operating a fleet, race team, or whatever type of application was appropriate. So pardon my cynicism.
Back in the '80's we had a hard time convincing some of the old timers in NASCAR to run a less viscous oil in qualifying because they were losing power to pumping losses in fluid friction using the heavier oils. The smarter ones caught on (most generally the more dominant teams) quick and, in a mode where 10ths of a second are important, every little bit helped. Then for the race itself they'd revert to a more viscous oil because of the prolonged operation at higher temp.
To some that seemed like radical think, yet today they've gone even further. I've been away from it as a career for over 16 years, so I keep in touch by surfing the net. You might want to read this to get a feel for where things have gone;
http://www.joegibbsracingoil.com/datasheets/81106.php . After reading that page, click on their "products" tab at the top and see what viscosity grades they're using in engines that turn higher rpms than you've indicated, and probably for longer periods and higher temps (?) than your race car. These guys invest a lot of time, money, engineering, and experimentation in power developement, with reliability being one of their major performance criteria. Yeah, they probably overhaul their engines more than you would ever think of, but they do it less so because of damage incurred (most of which is valve train related rather than bearing failure), rather more for maintaining peak performance in a hyper competitive venue where a lot of money is at stake (their measuring stick is VERY tightly defined).
One additional note about oil selection. In the past we were able to use "conventional" oils (i.e. the same ones that were generally available in the local stores) with considerable success. Today, if you're running flat rather than roller lifters, that is going to have to change. The additive in all qualified engine oils in years past that was most effective for protecting camshafts/lifters (zinc dialkyldithiophosphate or zddp) is not especially good for contemporary emmissions equipment longevity standards, so the amount in the newest of engine oils has been reduced. For roller lifters that's not much of an issue, but the higher frictional characteristics of "flat" tappet/lobe interface will not be happy with the lower levels of zddp in more severe useage. Quick note, no reason to panic if you've used the newer oil, it won't contribute to immediate damage, but you should look for a better replacement for next time. The way to identify oils with lower zddp is the API rating (decent explanation here;
http://www.advanceautoparts.com/engl...0030901og.html) on the lid or side of the bottle. If it's SL you probably don't want to use it long term. The compromise is if the oil also (or only) has a hd diesel (or C for commercial) rating. Currently these oils have a higher zddp level, but that will change when diesels require cat converters. Looks like, in the longer haul, we'll end up having to use "specialty" oils blended for non emissions/high performance/off road applications. As much as I generally think "snake oils" and "magic potions" are an unnecessary placebo for the uninformed, this situation may become a reasonable rationale for their use. We'll see in time.
