Doug MacRae said:
The Steve Maney crankcases are extremely strong and pretty much bulletproof- vastly stronger than a stock Norton crankcase: I twice cracked drive side bottom ends when I first started racing before finding the Maney stuff. That being said, I am one of the very elite few who managed to blow one up catastrophically when I had a rod bolt shear when I happened to be doing close to 130mph on the banking at Daytona last year- I put a rod through the front of the case and blew it to pieces. Didn't do me any good either, breaking pieces off my T3 to T6 vertebrae and knocking me out for a while. But I recovered enough to go to on crash two more times last season! Don't ask....
The short stroke that Herb built was actually a centre main bearing crank design of his own creation- very fast but needed lots of maintenance and suffered from some oiling issues with the centre bearing oil feed pressure.
I have used the throughbolt 850 style 750cc barrels which Walridge Motors used to sell (maybe still do? ...not sure) to good effect- much cheaper but of course much heavier than the Maney alloy ones which I have on there now.
Dave,
thanks for posting the pictures and info. I talked to Herb a while back about the engine, but the pictures are much more vivid.
I'm using Maney cases now, as well as the one remaining stock case with welded reinforcements, because I broke several stock cases back when I was racing Nortons. Back then, it was common for the stock case to crack on the drive side after enough flogging on the track. The crack would typically start at the back of the drive side case where it is thin, and progress around to the output shaft bearing bore. It looked like the top end was trying to pull the top of the case off. I had that happen on at least four cases (maybe more, my memory is not what it once was). I only had one case where the timing side developed a crack in the same area, and that was one where the crack on the drive side had gone all the way to the output shaft, and you could see a gap in the case. None of these engines broke from problems with the crank or rods, just from fatigue and lots of racing miles. The Maney cases are so sturdy, that I can't picture breaking one unless something gives out internally, like your rod incident.
I have only had one engine actually grenade. That was an original factory short stroke 750. They came with steel rods instead of the usual aluminum/steel design. If I still have one around, I'll take a picture and post it. Unfortunately, the factory decided they were too heavy, and lightened them (acid dip, I think). One of them broke at a race at Steamboat Srings, and sawed the cases to pieces. I found afterwards that the factory steel rods had a reputation for doing that. I quit using them, and switched to Carrillo rods. I've used the stock aluminum/steel rods in a lot of race engines, and never had one break. I have replace them when I found cracks around the pin end, and I've seen enough break in other engines, so I now only use the Carrillo rods. I still think the stock rods are pretty good, as long as you inspect them for cracks, and replace them every full season or so, but I'm not willing to take the risk myself. I used to have them shot peened, and had the rod Zyglo inspected, with the cap and bolts Magnafluxed every time an engine was apart. I think that helped a lot with the reliability.
Ken