Paul, the way that Evolution marketed their engines was confusing. The .455 does have the 'a' on the cylinder head, but it's not the Alpha. The Alpha is a .40 engine that can be upgraded to the .46. This is a strong engine. They all love 15% and hot plugs like the A3.The flywheel weight will bog down the engine. It's purpose was to improve idling, but this a great idling engine without that weight. I took mine off and threw it away. BTW, you can remove the baffle from the muffler and pick up power. If you have a Tower's Mufflermyou can pick up about 1000 more rpm.