McCoy .29 ? _ This is wrong, right?

Thanks Bandit,  I have seen them both ways too, and that's the problem as some have been disassembled before and who knows if they were put back together correctly.

 I have many of these McCoys and try to make a mental note about how they are arrainged when I disassemble them, but missed this one.  I will do the high in/low out and see if it runs, if not I will swap them.  

Bob

Roger that, while it looks OK in the pic and I don't see the top edge of the intake side of the sleeve protruding down in the exhaust (clear indicator that the sleeve is in backwards) its always good to check. BTW " its high out\low in" lol (bandit)

I experimented some more with the position of the cylinder in the case.  I don't think that it can be installed wrong because of the triangular arrangement of the three long cylinder head screws.  They dictate the correct alignment.  You can get it "wrong" but the cylinder port will not align with the exhaust of the case.



Anyway,  I put it back together and got it to run rather well for about 30 seconds, long enough to know that everything was correct.  Then it stopped on it's own and would not restart.  Somehow the compression went away, almost free-wheeling.  I retightened the head screws criss/cross pattern and the glow plug, still little compresson and no start.   Too bad, it's a nice looking engine but I have read where these McCoys may wear before your very eyes.  

is the piston still moving That is Nice Looking

Yes the piston moves. It has some compression and these do tend to lose "pop" when warm. I haven't given up on it yet.

I should explain, the first picture is just representative, they are two different engines but both are McCoys.

Yeah the top engine has a separate sleeve and can be put in backwards that's is why the newer engines have a locating pin on the top of the case that iindexes the sleeve in the right position. The steel cylinder engines are drilled in such a way to help make sure the cylinder can't be put in 180deg out about the compression, have you tried inspecting the sealing surface between the head and sleeve or top of cylinder? (Bandit)

Yes, all new gaskets including the head gasket. Also put in a new plastic con rod cap.

Aha...I found the culpret.  On a hunch I pulled the head to see if the gasket had been breeched, and it was.  Right at the baffle junction.





I replaced it, but it may happen again as appears there is a slight valley there in the gasket relief.  Or, it could be because two of the head screws were hogged out on the tighten side and I could not tighten them enough.  I had new replacements.  Gaskets are all Chellies quality gaskets.





Plenty of compression now.  Tomorrow I will give it another chance.

The two McCoys.  One for an add on fuel tank.

Cool glad you found the compression problem!
However one thing, I see that the head has been media blasted in the combustion chamber and sealing surface. It's not a good idea to media blast an surface that's used to seal espeshly areas that see high pressure bead blasting leaves millions of tiny little pits with each is a pontintial leak head gasket areas have to remain absolutely smooth and true as possible or the gasket can fail through hot gas leakage. The split at the baffle relief is a point that sees combustion pressure so the breach could of happened through being as you said not tight enough or a surface iregularity. If it does it again try a different head to see if if fails one more. You may find you might have to lightly touch up the area for the head gasket to smooth it out. Sorry bout the essay just trying to help. Hope this helps man. (Bandit)

Sorry doing this through my phone and autocorrect sucks lol.

No problem, I am thankful for your help.

Sandblasting, actually aluminum oxide the heads, case, backplates, and thrust washer are my SOP when rebuilding a model engine, haven't had a problem so far but will think about it.

The existing gasket was imbedded in the recess, and media blasting doesn't touch gaskets. I thought about just leaving it there and using another gasket on top of it. Maybe I should have.

rsv1cox wrote:No problem, I am thankful for your help.  

Sandblasting, actually aluminum oxide the heads, case, backplates, and thrust washer are my SOP when rebuilding a model engine, haven't had a problem so far but will think about it.

The existing gasket was imbedded in the recess, and media blasting doesn't touch gaskets.  I thought about just leaving it there and using another gasket on top of it.  Maybe I should have.  

finely my net is back up
It's good to always replace the gasket plus it would of lowered your compression anyway if you left it in there and placed another on top of it. You can try some permatex Copper Spray-A Gasket on a q-tip and spread a thin layer in the groove. That will help it seal I've done it before on my engines and full scale automotive head gaskets It's good stuff. If it's going to be a runner maybe upgrade to socket head allen screws too, they will give you a more positive torque for the head, keep the original one's though.
(Bandit)

Success.  It runs like a champion.  I ran it twice hand checking the compression after the first run.  Started right off on the second run, took a little coxing on the first until I found the NV setting that it liked.  



I also ran the .29, another rebuild.  I had trouble with this engine before not wanting to start, a fuel tank positioning problem I think.  This time it started right off and ran strong.  Likes lot's of needle though.  What a sweet little engine this is.



The .29 was swinging a 10/6 prop, the .35 a 9/4.  I should have swapped them but those were the props that they came with.  If I ever mount them in a model I wil re-prop them.  I used Sidewinder fuel, a model car fuel with 20% nitro.  I did not want to use my Cox 25% fuel.  Both ran well on it, but the battery is dead on my tach so I couldn't check the RPM's.

Did you add an castor to that car fuel? You should be at 25-28% oil on those engines.

McCoys are awesome ... I've got a couple 29s and three 35s

rsv1cox wrote: ...  I used Sidewinder fuel, a model car fuel with 20% nitro.

It took awhile for modelers to realize that the metallurgy used in the .35 requires a lot of castor...many use 28%-29%. If you use a low percentage synthetic lube you can expect a short life for that engine...some have posted that they wore them out in a weekend. Have not heard that about the .29.

Your engines, your choices but I would suggest 5-15% nitro and at least 25% all-castor lube for those engines. You put a lot of effort in restoring these engines, I'd hate to see you waste it. Remember those are 50's engines.

Good luck with them, whichever choices you make.

George
I've never met an engine I didn't like.

Thanks guys.  The only castor oil available locally is medicinal and I have heard conflicting reports about using that.  Should I ever mount these in an airplane and run them a lot I will surely find some.

I bought the .29 to use in this F4U advertized for C/L or R/C. The previous owner had built it for R/C and I am having difficulty figuring out how to make it into the C/L version without a major rebuild. Unfortunately the plans didn't come with it.



Bob

When you ordered the Sig Buster ... you should have ordered some of this.  Your McCoys will thank you for it!!

http://www.sigmfg.com/IndexText/SIGCO001.html

larrys4227 wrote:When you ordered the Sig Buster ... you should have ordered some of this.  Your McCoys will thank you for it!!

http://www.sigmfg.com/IndexText/SIGCO001.html

Now you tell me. ............ Let's see if they can add it to the Buster...

Brodak has it as well ...

Here is a nice conversion calculator ... I use it all the time.

http://www.nitrorc.com/fuelws/oilonly.asp

Thanks, I book marked it. Seems like there was another variation posted here on this forum not long ago.

Oh yeah ... there are several sites that do the same thing. I just happen to have that one bookmarked. Its always handy to have, especially when my local LHS is out of the regular fuel I use and have to pick up something different.

ALL of my fuel gets castor added to it .... even fuel for my modern .25 and .35 size engines. I even added some to my Sig 1/2A fuel I just got. Just alittle insurance policy for my engines ....

larrys4227 wrote:Brodak has it as well ...

Here is a nice conversion calculator ... I use it all the time.

http://www.nitrorc.com/fuelws/oilonly.asp

Thanks, I bought a quart of SIG's castor, not much more dollars than a pint when considering shipping. Using your calculator I come up with an additional 4.5 oz of castor to bring the oil content up to 25% on this partically used bottle of Sidewinder fuel. They don't identify the type of oil in the bottle.



Yesterday I repaired the flaps on this model I scratch built perhaps 40 years ago. I flew the dickens out of it then but haven't flown it since. It has an Enya .09 mounted and ran just fine on my R/C fuel at the time. Hopefully I can locate my flying buddy and get it back in the air soon.





I would think that the remix Sidewinder fuel would work as well in my Enya's along with my McCoy's and Green head K&B?

4.5oz of castor added to a quart sounds about right ... what was the starting oil content of the Sidewinder? 16%? 18%?

Your old engines will really love you for picking up and adding castor to the blend! Good job!!

How much Sidewinder are you working with? On my figurings with the calculator Larry shows, it says 3oz of castor to a pint of fuel will bring it to 25% total oil, and the nitro down to 16.8%. I notice the bottle states 10% oil. That's not much oil for these old things, so I hope your bench runs didn't cook the McCoys. With the added castor that should be a pretty good fuel blend to run these engines on. I buy 16% nitro 18% oil buggy fuel (all the local shop carries) and add castor up to 25% and all my engines love it. I also add extra nitro for my .049s. That calculator is great and really simple. Even though it says imperial measurements, it still works just the same for metric.

Rod