Derek Grubb in PA has a Buick GN powered 240Z and had an NA crank in his engine that lastest a few hundred 1/4 mile passes with no failure before he rebuilt the engine just to refreshen it. It went a best of
[email protected] and a perfect state of tune. NA crank remember!
Most of the passes were in the 10's but he did keep boost around 19-20psi and his car is a featherweight at 2550lbs.
I think the NA crank with careful tuning is safe into the 11's. Just don't go nuts with the boost. Personnally I would still rather run a GN specific crank to not temp fate.
GNX7
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2725lb '87 RX-7 w/ '87 GN driveline.
[email protected] on NittoDR +stk GN turbo
http://www.v8rx7.com/mark.htm