I don't agree about C20Let or C20XE is a no good engine for race aplication. Here in Brazil have a competition, the name is "thousand miles".. is 1000 miles of race, and have a prototipe with C20XE engine N/A, with 260hp(use carbs), and win all races in your category. Its wins BMW engines and Audi engines.
About the resistance of C20XE or C20Let, is the really good, let think:
- 86mm of stroke, have a good PMS(piston medium speed) in high rpm(can work 8.000rpm, without risk of crash)
-Good r/l relation of 0,30 and can be minimized to 0,29 with bigger rods, don't make vibration in high rpm, and don't need so strong rods like VW 2.0 engine with 0,32 of r/l relation
-Have 86mm of bore, is good capacity for a 2.0 engine, and possibility a good size of valves
-Have a good projected head(8V and 16V are nice if you compare others engines of segment), with good geometry of ports
-Have a strong block, without so heavy
And you tell me its not a race aplication engine? Man, here in Brazil most use a VW 2.0 engine, with 92mm of stroke, 0,32 or r/l, side flow head(is a **** head), and get out 550-600HP in races.
If the VW can do it, Vauxhall can do it much more easy and with more durability. The one advantage of VW is the torque, because the bigger stroke, can make a better torque and power curve.
-JE forged pistons
-Total seal rings
-Crower forged rods
with this parts i believe C20XE can make 500hp for street use, without risk of crash. Logical its need a good project, for have a good MEP(medium efetive pressure) and PMS. If you make 500hp@ 5.600rpm, logical this engine will crash. But if you make 500hp @ 7.300rpm example, you have a nice MEP, and the internal forgeds parts will resist easy.