McCoy Plug Location

Is there any discernible difference in running characteristics for a center vs. off-set plug in a McCoy .35?

Eugene S. Chernosky
AMA 639635

VI,
Can't say for sure since I have never run a center plug 35, but Currell has mentioned McCoy "plug position" several times here, I hope he gets up soon, and posts!
Bill <><

Bill: In the Summer of '99, I ran an experiment on this, at least as far as bench testing was concerned.

I took a dead stock Redhead, and ran the following heads on it:

1. Plug smack in the middle, just like the earliest ones, from 1957 (no bosses on the venturi sides) through 1961.

2. Plug offset to the exhaust side, and slightly forward, the variation for 1961. It also is screwed into a raised boss.

Now, the "mistake" heads, although I have been told here that Dick McCoy actually deliberately released variations of his engines into the marketplace from time to time...

3. Plug offset to the exhaust side, but ever so slightly AFT. I have never seen another like this.

4. Plug actually offset to the BYPASS side. I have never seen another, and I swapped a guy for this one.

I ran them all on one motor, within, say, 25 minutes of one another, and tached each.

Results: No difference, peak rpm wise. Starts about the same, all quick.

On the last (4.) one, offset to bypass, it was, maybe, 200 rpm off. But I might not have cinched the head down tight enough. Or something.

Did plug placement make a difference as far as innoculating the Redhead against the Dreaded Fox Burp, experienced during Outside maneuvers?

Don't know.

Closest thing to Science that I can provide...

Currell

(Question, to anyone...All of my McCoy 29s, even the last Lightning Bolt model, have the plug still smack in the middle. Is this correct? Go check).

Currell,
I checked my 29s. I have three RH, and 1 RH LB, all have a center plug, and do my four 19s.
All my 35s are offset to exhaust side, front.
Bill <><

Bill: Interesting...they changed the plug location on the 35s (and I think the 40s; mine are offset).

But not the 29s.

Maybe that fits in somehow with my "no difference" conclusions.

Or you could say...if it makes no difference, why change?

(Once again, flying characteristics could be different. All I did was bench run).

As a collector of McCoy's I have 4 NIB 29'S Three have the plug in the center and One Offset. SO one is the SPORT model and the Others have .003 more subduction then the Offset plug. McCoy made an Custom and a stunt model one was priced at 7.95 the other 12.95. Just something I learned years ago.

Scott(uncle worked for Dick McCoy in 1959-1962)Riese

Hi Scott,
Typing at the same time! LOL!!
So.... there IS an offset plug 29!
Thanks,
Bill <><

I have ONE .29 with an offset plug. and Only seen one with an offset plug

Currell,
I have three RH 40s and a Blue Head RC 40, they are all offset like my 35s. (need a venturi to convert the blue head!)
Don't know why they didn't do it to the 29!
Bill <><

Once upon a time, about 20 years ago, Dick McCoy told me he thought the offset plug head was a "little better for stunt". I can't tell any difference.

>Is there any discernible difference in running
>characteristics for a center vs. off-set plug in a McCoy
>.35?

Ed Southwick was the catalyst for the development of the McCoy Red Head Stunt engines by Dick McCoy in the mid/late fifties. Ed was flying at a schoolyard in Pomona in about 1955 when Dick McCoy stopped by to watch. After watching a few flights Dick approached Ed and asked him if he was satisfied with his engine (Ed was then flying a Green Head Torpedo .35). Ed said that he was not, Dick asked if Ed would be willing to try a new engine if he (Dick) gave it to Ed, Ed said that he would, so the development of the McCoy .35 Red Head stunt engine began.

Ed worked closely with Dick on the development of the Red Head .35, from which all of the other sizes of the Red Head stunt series engines were developed. One of the things that took a lot of time was getting the engine to run well and exactly the same in both inside or outside maneuvers while mounted either upright or inverted (as opposed to being mounted on its side in a profile).

Dick and Ed did a lot of flight testing of various cylinder head configurations, a large part of which was the location of the glow plug. The best location for the glow plug turned out to be forward and to the exhaust side of the head, and that became the standard location of the plug on the .35's and .40's. The .19 and .29 remained in the center.

Ed would bring two or three airplanes to the field, each with a different engine/cylinder head configuration, and sometimes change engines and/or cylinder heads in his airplane at the field so that he could test the various setups. I was the 12 year old kid that Ed would pick up and take to the flying field so I got to watch most of this stuff as it happened.

Probably more info than you wanted or needed but it was interesting to me that somebody would ask about the plug location on the McCoys these days, and I happened to be there when the location was being determined.

Great info, Bill. Since I couldn't get any rpm differences on the ground, it had to be in air performance that caused the change.

Hello All

Great History and insight into the testing that was done. I wounder if todays head shapes variety of plugs has made the plug location irelivent? It is easier to make a head with the plug in the middle.

Also combustion chambers have changed since then.

It is too easy to look back with todays eyes and think that things were easy then but reading insights like this those blokes worked just as hard to do the best they could and win.

John Quigley