SR's are more reliable than ("ANY") RB Engine if you plan on making more power than stock.. (With an RB).....There is a common oiling problem with the RB20,RB25,RB26 Series 1 & 2 motors, as the surface where the crankshaft meets the oil pump was machined too small, eventually leading to oil pump failure at high rpm. This issue was resolved in later versions of the RB26. ("So they say.") But God only knows when you get the engine which one it will be. It snaps and twists the oil pump gear, shreds it, breaks it in half... No oil pump, locked up engine. And not to mention the turbochargers on them are "FAIL". Ceramic Exhaust turbine and a plastic compressor (45V4 is plastic, 45V1, 2 and 3 are all steel.. however ALL exhaust wheels on the 45V's are ceramic).. Not joke. They will explode past 14psi. And yes they make a aftermarket crankshaft collar to fix this. But the crank has to be machined and this collar pressed+1 set screw and weld to be safe. Loads of money.