This is a good thread, and there are some good answers. But I feel strongly that Joel's comment about oil may be the key - after all, a good crank and good, brand name bearings properly installed should live a good long time under most (key word, most) circumstances. The variable element here is the oil, especially under the operating environment (alcohol for fuel) that they are.
Alky (and nitro) are many, many times more corrosive than gasoline. In addition, they are both much stronger solvents, which tend to dilute the oil faster. Why does this happen? Two reasons:
1. The fuel "washes" the cylinder walls clean of the oil and reduces ring seal, so more of the fuel gets into the oil pan (also causing a slight loss of power).
2. The diluted oil/fuel mixture breaks down the oil faster which results in 'wiping', 'flaking' and other bearing problems, all of which result in premature wear and failure.
Since most racers regard oil as an afterthought, or something that they get free at the race and pour into the engine ("hey, it's just oil, right? It doesn't matter what it is....."), bearing/crank/piston failure is often attributed to the PARTS instead of the OIL. There IS a difference in oils, belive me. It's the lifeblood of your engine. Let me give you an analogy.
Go to the hospital and get a blood transfusion with a different blood type. Then go home and put an off-the-parts-house-shelf 20w50 into your highly strung alky/nitro engine. Take it racing for a weekend. Well, actually, you won't be able to - you're either dead or very, very sick in the emergency room because you have the wrong blood type. So your buddy takes the car out and runs it whilst you recover (assuming you do). Figuring it's new oil, he doesn't really check it and doesn't change it, thinking you will Tuesday night. Unfortunately, it kicks the rods during the first round of eliminations. The oil is babypuke yellow/green and ultra thin, and all the bearings (at least the ones you can find) show signs of direct metal contact with the crank.
What's the cause? Wrong fluid in the body/engine. Alky engines need an oil that can maintain a higher ring seal and resist cylinder wall 'washing' compared to gasoline - in other words, an oil that STAYS on the cylinder walls. Off the shelf 20w50 has no hope of achieving that goal. So the crankcase loads up with alky (or nitro). Because you have a good high-volume/high pressure oil pump, it really never shows signs of oil pressure loss until it's too late and boom.
What am I leading up to here? You guessed it - you need the right kind of oil. Unfortunately, due to intense and clever advertising, huge giveaway deals at bigger races and generous contingency programs, you probably aren't running the ONLY oil that has been engineered from the beginning to solve this upper cylinder wash and oil dilution problem - Torco with MPZ© (yeah, you knew this was coming!). But it's true. Most of the stuff being given away out there is not engineered for an alky or nitro engine, and some of it is just plain JUNK! I'm not going to step into the gutter and name names, that's unprofessional..... but there are a lot of racers out there that have learned the hard way about oils, and now BUY Torco instead of taking the free stuff. Many of them (especially in NASCAR, which doesn't even use alky as a fuel) are heavily sponsored by other oil brands but run Torco (with those other brands' approval - why should they care what's actually in the engine? The public doesn't know.) On the average, about 30 of the NASCAR teams out there every weekend have Torco in the crankcase, transmission and rear end. But whatever, we don't care about NASCAR.
There are a LOT of Nostalgia teams who buy Torco, many of them from me. Some of them are on this message board. They know it costs a lot up front, but they also know it saves them money in the long run. If any of them want to speak up, fine, but I"m not going to ask them too. All I know is I'm glad to help these racers and proud to know what they're running that helps them win.
Jeff, I have no idea what your clearance setup is, but I'd be willing to wager that if you'd put Torco in your crankcase after talking with someone as to the correct oil for your application, you'd get significantly longer bearing/ring/piston & crank life - and get a little more horsepower due to the increased ring seal. Based on what little I know of your application, I'd use Torco Semi-Synthetic T4R 20w50. The T4R has a small amount of an additive that does a great job of increasing the ring seal with alky & nitro, even more so that the regular TR1 straight petroleum oil. Both have Torco's exclusive MPZ© which is the 'magic' that keeps the cylinder walls from washing and causing oil dilution.
OK, off the soap box. Visit
www.torcousa.com for additional information, or email me.
We now return you to your regular programing.
Hal Sanguinetti
TNT Distributing/Torco Oils
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