stunthanger.com
Engine basics => Engine set up tips => Topic started by: raglafart on July 07, 2008, 08:05:56 AM
-
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
-
TTBOMK, my Lightning Bolt 40 has / had the original RH-type piston (I write it that way because I haven't seen the silly thing in years, but also am certain I never gave it away, sold it, traded it, or trash-canned it.)
-
John; I have 2 McCoy 40 red heads, and they both have the domed sintered iron pistons with the inverted V baffle.
-
George Aldrich did some McCoy 35's back in the 80's. Innards replaced - could your engine be one of those?
-
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.
-
Hi Guys
Thanks for the replies. This engine hasn't been touched by George, that's for sure! like I said, the baffle wasn't parallel to the wrist pin by some 5 degrees and someone had left some rustic file marks blending in the transfer port.
I've honed the bore and made a new piston and am just about to run the motor this morning having finished a bit too late to run it last night. Will see how it runs in a moment. The reason for the question was that the deck heights are a little strange with the cylinder head arrangement and height of the baffle. Can't run a decent height baffle without running into head clearance problems, the domed piston answers that question.
Cheers John
-
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
-
HiJohn
Can you tell what material the piston is made of? Bar stock ???? or is it machined cast iron?
Regards
Randy