Author Topic: McCoy Redhads with very litttle compression? (Read 3893 times)

frank mccune · « **on:** August 31, 2015, 07:45:33 AM »

Hi All:

Is there any way that the compression for McCoy Redhead engines can be reestablished?

Tia,

Frank McCune

Jim Kraft · « **Reply #1 on:** August 31, 2015, 11:52:40 AM »

Yeah Frank. But you have to be carefull to keep from braking the piston. I have done this to many of them without breaking one, but there is always a first time. The best way is to remove the cyl. and piston and place the assembly on an anvil or hard steel surface with the piston at the bottom of the cyl. Then take a large like 1/4" punch and place it on top of the piston dome and hit it gently with a light hammer. It will spread the top of the piston and restore compression. If it gets to tight you will have to lap it in again before running. The secret is to just tap it a few times and check to see how tight it is. When you get to the place that it drags pretty hard at the top of the cyl. it is good enough. Keep it rich for a while till it gets broken in again and it will last a long time.

frank mccune · « **Reply #2 on:** August 31, 2015, 01:33:52 PM »

Hi Jim:

Thanks for the reply. I have heard of doing this but I was a bit hesitant about striking a sintered piston. I will try this and see how it goes.

Be well my friend,

Frank

Tim Wescott · « **Reply #3 on:** August 31, 2015, 01:42:39 PM »

Quote from: frank mccune on August 31, 2015, 01:33:52 PM

Thanks for the reply. I have heard of doing this but I was a bit hesitant about striking a sintered piston. I will try this and see how it goes.

What's the value of a piston that's too damned small over the shattered remains of a piston? Unless you think your can convince a plater to ply it with hard chrome and make it bigger, you have little to lose and much to gain.

Brett Buck · « **Reply #4 on:** August 31, 2015, 01:51:18 PM »

Quote from: Tim Wescott on August 31, 2015, 01:42:39 PM

What's the value of a piston that's too damned small over the shattered remains of a piston? Unless you think your can convince a plater to ply it with hard chrome and make it bigger, you have little to lose and much to gain.

http://www.hobbypeople.net/index.php/magnum-xls-25-two-stroke-rc-engine-rnv.html

Brett

Tim Wescott · « **Reply #5 on:** August 31, 2015, 02:06:31 PM »

Quote from: Brett Buck on August 31, 2015, 01:51:18 PM

http://www.hobbypeople.net/index.php/magnum-xls-25-two-stroke-rc-engine-rnv.html

Brett

Well, yes, but that's not a Valuable Antique like a McCoy. I mean -- there's eBay dealers who will sell you a "vintage" McCoy engine; they won't be listing that Magnum engine as "vintage" for at least, oh, two weeks.

frank mccune · « **Reply #6 on:** August 31, 2015, 03:45:28 PM »

Hello All:

Tim! Stop talking like that! You are making sense! Lol I may go one step farther and ask, "What good is a good running McCoy .35 RH! Lol

I pulled the McCoy from the plane and noticed that my OS .30S will fit the existing mounting holes. No brainer!

Brett. I thought that Magnum engines were not available due to cessation of production. If so, spare parts may be a problem. A 9oz. .25 engine?

? It better be a powerhouse! I thought my "new" HP .40 engines were heavy at 9 oz.!

Be well my friends,

Frank

Bill Johnson · « **Reply #7 on:** August 31, 2015, 04:06:27 PM »

Hi, FranK!

I had recently read a thread that talked about "growing" the piston by heating it in an oven. I can't find that exact thread but here's one like it:

http://stunthanger.com/smf/index.php/topic,9469.0.html

It might pay to research that before you try the other method. Good luck!

Bill Little · « **Reply #8 on:** August 31, 2015, 04:30:15 PM »

Hi Guys,

I have never tried Jim's "tapping" method but I am sure it will work. Why? because it makes sense and Jim does it! What ever that gentleman does to old engines just plain works

I have cooked a few, and some of those did fine. Some it did no good. So I can testify that it *might* work.

I will get out the hammer and punch next time

Bill

Tim Wescott · « **Reply #9 on:** August 31, 2015, 05:02:36 PM »

Quote from: frank mccune on August 31, 2015, 03:45:28 PM

Brett. I thought that Magnum engines were not available due to cessation of production. If so, spare parts may be a problem. A 9oz. .25 engine?? It better be a powerhouse! I thought my "new" HP .40 engines were heavy at 9 oz.!

ASP engines are, to my meager knowledge, in current production and are basically the same thing.

And yes, the specs at least make them look like freaking powerhouses.

The OS 25AX is in the same class (it's probably what they copied), for about 50% more moola.

frank mccune · « **Reply #10 on:** August 31, 2015, 06:37:23 PM »

Hi Al:

Back in the early 70's, I tried growing worn out Fox pistons and here are my results:

Heated to dull red and quenched in oil or brine. These warped to a point where they were useless. They also became very brittle and shattered when run. The oil also produced a very hard scale that was difficult to remove. No, it did not form a seal where the piston could be lapped into the cylinder. The wrist pin holes became a laugh a minute when coked up with this coating of burned on oil

Heated to 700 deg.F for 24 hours and permitted to air cool. This did not make the piston grow enough to be useful.

Then there was knurling! This appeared to form stress lines where the pistons would break. It did increase the size of the piston to enable the piston to be lapped to size but he piston broke very easily. I do not think that longevity of a knurled piston would be great.

I was on the wrong track I think. Perhaps I should have made an adjustable die that the CYLINDER could be pressed through to size it a bit at a time until it was reduced in size enough to enable the piston to be fitted to the cylinder. I hear that there are things called axle nut that come in different sizes that may be used for this. Anybody know what these axle nuts are and where may they be purchased?

Thanks for the replies,

Frank McCune

Tim Wescott · « **Reply #11 on:** August 31, 2015, 06:46:39 PM »

Hey Frank -- why not just get some cast iron rod and make new pistons?

John Cralley · « **Reply #12 on:** August 31, 2015, 08:22:36 PM »

Chrome plating is tough to do (leave it to the pros) but nickel is said to be relatively easy to plate. I have never done it although I have gathered the required parts. You can get the chemicals from eBay and a piece of nickel. Directions are on the WEB as well as how to videos.

Don't know how long a nickel plated piston would last but might be worth a try.

Jim Kraft · « **Reply #13 on:** August 31, 2015, 08:42:23 PM »

It is my understanding that the reason McCoy Red Head pistons do not grow with heat is because they are sintered iron put together with heat. There is nothing left to grow. I have grown Super Cyclone pistons with heat and it worked very well. I just used a torch and heated it till dull red and dropped it in a can of engine oil. It has been running for a long time now with great compression. Way better than it had when new. Some pistons are heat treated at the factory and they will grow no more. The only way I know to find out is to try.

Tim Wescott · « **Reply #14 on:** August 31, 2015, 08:44:41 PM »

Quote from: Tim Wescott on August 31, 2015, 06:46:39 PM

Hey Frank -- why not just get some cast iron rod and make new pistons?

Better yet, put the engine up on eBay as a Valuable Antique (Good Bearings! Spins Freely When Flipped!). Then buy something new.

Motorman · « **Reply #15 on:** August 31, 2015, 08:52:29 PM »

I have a friend who had his engine rebuilt buy a guy across the pond. I've never seen a better running McCoy 35 and he has it on a PDQ Lion Tamer.

Anyway, the thing he does is to hone the sleeve to spec and make a new piston to fit. If I remember the name I'll let you know.

MM

Jim Kraft · « **Reply #16 on:** September 01, 2015, 09:24:31 AM »

I just did a lightning bolt 35 that runs almost as good as the 40's I have been running. It has super compression and pulls like crazy. It fly's my 38 ounce Magician with very consistant running everywhere. Of course, I am biased toward old iron so take that along with whatever I say. Sure runs way better than any FP 40 I have run.

Tim Wescott · « **Reply #17 on:** September 01, 2015, 10:08:32 AM »

Quote from: Motorman on August 31, 2015, 08:52:29 PM

Anyway, the thing he does is to hone the sleeve to spec and make a new piston to fit. If I remember the name I'll let you know.

What spec? Somehow I don't think he hones it until the ID is back to stock -- rather, I assume he's honing it until it's either dead straight or tapred to his satisfaction, then making a piston to fit.

A McCoy with an ABC piston/cylinder set is something to contemplate...

Motorman · « **Reply #18 on:** September 01, 2015, 10:28:21 AM »

Quote from: Tim Wescott on September 01, 2015, 10:08:32 AM

What spec? Somehow I don't think he hones it until the ID is back to stock -- rather, I assume he's honing it until it's either dead straight or tapred to his satisfaction, then making a piston to fit.

Well, spec is somewhat of a slang term that one can assign different meanings to. My spec is round within 100 millionths and tapered .0015 over the length of the sleeve. Of course honing makes it bigger so you have to make a bigger piston, which is common knowledge. The only way the bore can get smaller is if you run the hone in reverse and apply voltage.

MM

frank mccune · « **Reply #19 on:** September 02, 2015, 07:15:35 AM »

Hello MM

How do you measure to 100 millionths?

Frank McCune

Bill Johnson · « **Reply #20 on:** September 02, 2015, 08:18:36 AM »

Quote from: frank mccune on September 02, 2015, 07:15:35 AM

Hello MM

How do you measure to 100 millionths?

Frank McCune

That's .0001 to us regular folk

A good micrometer will measure to that.

Gerald Arana · « **Reply #21 on:** September 02, 2015, 09:19:41 AM »

Quote from: Jim Kraft on August 31, 2015, 11:52:40 AM

Yeah Frank. But you have to be carefull to keep from braking the piston. I have done this to many of them without breaking one, but there is always a first time. The best way is to remove the cyl. and piston and place the assembly on an anvil or hard steel surface with the piston at the bottom of the cyl. Then take a large like 1/4" punch and place it on top of the piston dome and hit it gently with a light hammer. It will spread the top of the piston and restore compression. If it gets to tight you will have to lap it in again before running. The secret is to just tap it a few times and check to see how tight it is. When you get to the place that it drags pretty hard at the top of the cyl. it is good enough. Keep it rich for a while till it gets broken in again and it will last a long time.

Hi Jim,

I was given an old lightning bolt McCoy 29 with weak compression. Of course I had to try your method of tightening the piston. Tapped it a few times........nothing. Tapped it a few more times, voila tighter.

Ok, so now I tried to run it for a couple hours, resting between flipping and popping. It would start to go then stop abruptly. Prime it and start all over again.

New plug, same thing. While adjusting the NV, I noticed it was rather loose. I put in another NV (from another engine, ST type) and got it to run for almost a minute. But, it acted like the piston started to bind/heat up and stopped.

I'm going to try it again today and if I fail to get it working it'll go in the junk drawer with the rest of the antiques....... (read that as junk)

dennis lipsett · « **Reply #22 on:** September 02, 2015, 10:33:40 AM »

I'm probably going to get roasted for this or called a know nothing but surprisingly after repairing about 3 dozen of the red heads most of them did not need piston resizing.
The engines are notorious compression leakers but as long as there is pinch of any amount at the top it will run if.....
Get rid of all those cork, paper or other unworkable gaskets. Use a high temperature silicon sealant instead. This has two benefits. One it will never wear out or shrink and you will also lower the cylinder about .001 lower into the case giving an increase in compression. Make sure that you fill the space in the head gasket groove with something that will work with heat and then use the sealant to make the head to case seal. While your at it replace all of the screws with 4/40 cap screws and take the time to accurately snug the head and cylinder to the case.
OK so how does it work. Well out of 24 engines done over the years most started up on the 2nd or third flip and ran fine. Just remember to use about 24/5% oil and no it doesn't have to be all castor and be light on the needle settings. Most expert or amateurs like me can not overcome destroyed fried parts. If you lose the nylon end cap pin for the shaft I generally use a small piece of hardwood dowel rounded at the nub to replace it. So far with hand cranking they seem to go a long time.
You have nothing to lose by trying this method first before going to extreme methods. I also agree that heating the piston to 500 degrees is a waste of time. However I have tapped 2 or 3 pistons with success. Go slowly and don't get impatient doing it. Better to have to lap it then throw the wreck away.

Dennis

Gerald Arana · « **Reply #23 on:** September 02, 2015, 11:40:54 AM »

Quote from: dennis lipsett on September 02, 2015, 10:33:40 AM

I'm probably going to get roasted for this or called a know nothing but surprisingly after repairing about 3 dozen of the red heads most of them did not need piston resizing.
The engines are notorious compression leakers but as long as there is pinch of any amount at the top it will run if.....
Get rid of all those cork, paper or other unworkable gaskets. Use a high temperature silicon sealant instead. This has two benefits. One it will never wear out or shrink and you will also lower the cylinder about .001 lower into the case giving an increase in compression. Make sure that you fill the space in the head gasket groove with something that will work with heat and then use the sealant to make the head to case seal. While your at it replace all of the screws with 4/40 cap screws and take the time to accurately snug the head and cylinder to the case.
OK so how does it work. Well out of 24 engines done over the years most started up on the 2nd or third flip and ran fine. Just remember to use about 24/5% oil and no it doesn't have to be all castor and be light on the needle settings. Most expert or amateurs like me can not overcome destroyed fried parts. If you lose the nylon end cap pin for the shaft I generally use a small piece of hardwood dowel rounded at the nub to replace it. So far with hand cranking they seem to go a long time.
You have nothing to lose by trying this method first before going to extreme methods. I also agree that heating the piston to 500 degrees is a waste of time. However I have tapped 2 or 3 pistons with success. Go slowly and don't get impatient doing it. Better to have to lap it then throw the wreck away.

Dennis

Dennis,

Those are really good suggestions. Thank you.

Jerry

Jim Kraft · « **Reply #24 on:** September 02, 2015, 05:14:13 PM »

I do replace the fiber head gaskets with aluminum cut from .008" sheet from the news paper office. The 35's I have worked on usually take two of these as they are over compressed with one. If the fit is to tight I lap them in with Dupont #7 polishing compound and oil to where the piston will go to within about and 1/8" from the top of the cyl.. I remove the rod and put the wristpin back in the piston and fit a clothespin into the bottom of the piston backwards to twist and push the piston into the cyl. The clothespin will not turn past the wristpin and it makes a good handle for twisting and pushing the piston.

Do not use the rod as you will probably break it or twist it. If the piston gets stuck in the cyl. tap it back down from the top. Make sure to keep it running very rich for the first few runs to keep it cool and let it wear in slowly. I have had good success with around 30 or so of 29's, 35's, and 40's. I did have one that I think the cyl. and piston were so scored so bad that I never could get it to seal.

The info from Dennis is very good also. If you work carefully you can make these old Red Heads run better than new. They have a very consistant run from the first of the tank to the end on uniflow. Some of the 40's like an open vent tank better.