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I've got some +.060 pistons and I'm starting with a std block that needs about +.020 to clean up the ring step at the top of the bore. This is for a banger "race" engine using a gt15 turbo that will be asked to race for 8 hours with only one stop for fuel. Then repeat it the next day.
Reliability has been an issue for us, since our budget for the whole car is only $500 USD so there's no high dollar parts or machining here-- just used stuff and the occasional ebay "score". And all of the drivers can't exactly be described as "mechanically sympathetic".
I've done some reading using the search feature and it seems the jury is "out" on whether it is beneficial to offset bore for any reason other than to fit the 8v bmw head, but I thought I'd ask again.
My reasoning for wanting to do this is every head gasket failure I've had in a NA road 998 is because of a burn through between 3&4 and occasionally between 1&2. On 1275 motors it's been burn through between 2&3-- these are all the thinnest parts of the gasket. My thinking is if I can maintain the spacing of the bores between these thin spots, I would be better off.
Now I know that the burn through is a result of poor fueling that can be caused by leaking valves, bad rings, poor fuel quality, detonation, etc, and that an engine in good nick shouldn't suffer from this... But any/all of this happens to the motor over the course of a weekend of banger endurance racing.
Boost levels have been about 8psi but we're looking to turn it up to maybe 12, and we're going to go from a stock cam to maybe a locally ground "255"
I'm wanting to move bore centers of 1 & 4 to the outside of the block, and 2&3 to the inside of the block.
What say you, the jury? Is my reasoning.... um, errr... reasonable? Or am overlooking something? I don't think I'd need to worry about the rods as there seems to be enough float there...
Edited by Spank on 24th Jan, 2012.
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