Some comments and opinions:

McCoy Redheads (front intake) were an excellent design. The first ones ran well. I understand that due to the "engine wars" at the time, McCoys were eventually assembled by not necessarily skilled people and fits suffered. Sometimes you got a good one, sometimes a bad one. George Aldrich also said that what killed many of them was the inferior lube in Testors 39 fuel...get the connection, cheap engines, cheap fuel = worn out quickly. Most of the cheap ones were bought by inexperienced people who did not know how to break them in. I currently have a couple of the good .35's. I'll have to fess-up to using Testors 39 back in the day also.

BTW, during those price wars, K&B came out with the "Stallion" series and Fox came out with the "Rocket" series. These engines used no bronze crankcase bearings, and some other "cost cutting" shortcuts. (Fox STILL made the stunt .35 during this time.)

I believe the McCoy blue heads were RC and the lightning bolts were constructed better. I think the lightning bolts have a better crankcase bearing.

The Series 21 was never really accepted well because of the weight induced by the massive square crankcase. I have a couple of .19 CL's.

George