Can anyone tell me if the Red Head McCoy 40's used the sintered pistons similar to those used in the 29 and 35's with the raised or domed piston crown with an inverted V  baffle molded into the piston crown or did they have a bar stock piston with a flat crown and right angle baffle more like the Fox 35's and OS 35's. I have an engine I'm working on for a friend and it has a bar stock piston that doesn't appear to be original. What makes me think it may be a home brew job is the fact that the baffle is not parallel to the wrist pin and is out by at least 5 degrees!
Note; this is a lapped piston sleeve Red Head McCoy 40 and an early one at that with the slotted front lug holes, not a lightening bolt engine or a later Series 21 unit.
I found a picture of the later one without the slotted front lug but apart from that it's identical. It's a 1965 version according to my American model engine encyclopedia
Cheers John Goodwin

John; I have 2 McCoy 40 red heads, and they both have the domed sintered iron pistons with the inverted V baffle.

George rebuilt 40-some-odd McCoy 40s all in the same time frame for resale as "McGas" Customs, with chrome cylinders, charcoal gray anodized cases, and black heads.  I cannot recall the piston choice that was involved, but if he'd worked on this one, the baffle would have been lined up with the ports.  A McGas engine had its name, and George's initials, engraved onto it. 

  John,  If you have access to old model mags, check the January 1967 issue of M.A.N. In it, Peter Chinn  checks out the McCoy 40 Stunt engine. In the article he mentions that there was at least one production run of RC 40 engines that used a meehanite bar stock  piston. He described it as having a flat crown and a somewhat taller baffle than the standard sintered piston. He also mentioned that the flat top piston was slightly shorter in the wrist pin to top of crown dimension, than the standard piston. It would appear you are looking at one of that production run. Hope this answers your question.

Al Burczycki