Sounds right to me..
There are DIFFERENT kool bore blocks.. Like the Raptors and newer motors have a lot bigger valve guide area, and the third bolt hole for the carb.. The BLOCK itself has more aluminum in it, therefor it's a little bit (stronger) all around... But if you use the older 1974 style block....
You still are never gonna explode the engine block, unless you go building some retarded monster engine....
But then you'd be running something sleeved anyways with bearing crank.. If you want to build ANY kind of racing motor and plan on getting it hot and spinning the hell out of it, you might as well just buy a sleeved engine to start with, as it will have a hell of a lot longer life trying to be an airplane motor it was never intended to be...
There are buhed and ball bearing engine blocks as well... Most people want to use the dual bearing engine when talking about high RPMS
But there is ALSO an engine block (DU bushing) which is a bushing block, BUT the bushing is made from a bronze/oil brass, type material, to reduce friction and ad a lot more life to the block.... So it is better than a standard aluminum bushing in that respect, but still is a bushing and offers a bit more drag than a ball bearing... So you'd want maybe a ball bearing over DU bushing for going 11,000 rpms.....
BUT I have heard from Gokart racing guys that in ALL REALITY, the DU bushing block is the strongest block, as it has much more aluminum engine block material holding the DU bushing in place.... The GAIN in very little friction loss that you gain by using a dual bearing engine....
ACTUALLY DOES NOT out weigh the block strength of the DU block..... And when you are talking about building 11,000 rpm engines, The DU bushing works just fine and is no problem with drag or oiling...
But a Dual Bearing engine block, built the same way, will explode, because there is far less aluminum engine block, because it has all been cut away to make room for the ball bearing.....
So in a perfect world I guess you want a DU Bushing iron bore block, which is not a Raptor.... It would just be some unsuspecting 1992 Briggs 5 horse Industrial Plus motor bolted to an air compressor somewhere...
Then ya gotta take the junk crank out and replace it with an old 70's 80's one...