Magnum .36 A bit of Trouble

I tried a Magnum .36 off & on for a year or so had one problem with it. It would flood & quite in the intersections of the Horizontal 8 & square 8 also it might kill at the bottom of the Hour Glass,bottom of the Verticle 8.
I ran a .280 venturi Bolly 11x4.25 (which was best)at 10,600 & a .250 venturi with a Bolly 11x4.25 at 10,600 SigChampion Fuel,Powermaster Fuel,(GMA 20/20) Byrons fuel quite a few different combinations. Different plugs Thunderbolt 4 cycle,rclong,standard lond,Fox Miricle plug,OS type F,etc.

I bought a new style .40 by Magnum (square Barrel) it floods out evan worse they are nice in level flight but flood in the intersections.

I like these engines but I cant have this flood quit deal going on.

P.S. yes I've talked to Phil,Mike Haverly .

John,

I don’t remember talking to you about the problem (sometimes it’s hard to remember the entire pattern….(NO Comments from peanuts in the gallery please) Anyway; the week before Golden State I had this same kind of flame out problem on an engine I had been running for about a year. It would actually flame out in level flight sometimes after just one lap. Tried changing tanks, plugs and a variety of things with no success. Finally, replaced it with the first Magnum I used 3 years ago and even though that engine has over 100 hours of run time it is still as strong and consistent as ever.

I’m not one to let sleeping dogs lie and had to know what the problem was since it seemed to develop quite suddenly. I mounted it on the test stand started it and in about a minute it flamed out again! From past experience I knew this kind of thing is usually the result of a leak somewhere but I just couldn’t find it. Finally, I wiped the engine completely dry with alcohol started it and just watched to see if I could find a leak. As I looked at the back of the engine there was a drop of oil on the bottom of the case at the back plate. Every time I wiped it off it would magically reappear. Once it flamed out and cooled off I cleaned my hands and gave it the clean finger test. No oil anywhere except at the back-plate, which is the usual suspect. There is a very thin plastic gasket there. Since I had a couple of extra engines with me I just replaced the back-plate with one from another engine. Presto, no more oil leak, 200 more RPM at same needle setting and no more flame out. Closer inspection of the original back-plate revealed a slight wear pattern from the crank pin. Conclusion, when I replaced the rear bearing (bearings seem to be the one weak spot of the engine) it was not seated properly so when the back-plate screws were tightened the crank pin caused it to deform slightly. This same kind of thing could happen to your engine if: It was bolted onto mounts that were not square: You removed the back-plate and retightened it with the wristpin or crankpin not seated perfectly: You crashed your plane: The gasket is blown: Your bolts are not tight: Some one runs over it with an SUV: Your aunt Minnie that you made fun of as a kid, sneaked into you shop and hit it with a ball-peen hammer! ……bla, bla, bla

I'll bet a couple of blind folded, left handed flights inside the crater of Mt. St. Helens on Rush's Impact; the back-plate is the culprit.

Phil

Phil,
I talked to you in Sacramento in April however I didn't at that time disclose my problem. Thank you for the list to check. I have an idea it is the back plate & that Ruthaford took his own personal Ball Peen hammer to my engine while I had my back turned because of my political veiwes.

> Phil,
> I talked to you in Sacramento in April however I didn't at
>that time disclose my problem. Thank you for the list to
>check. I have an idea it is the back plate & that Ruthaford
>took his own personal Ball Peen hammer to my engine while I
>had my back turned because of my political veiwes.

John,

While it was not the preponderance of "Kerry" stickies on your vehicles and even your personal clothing, I did in fact use your engine as the receptacle for an impromptu urine test. Hey, somebody walked off with my Snapple bottle. Hope they didn't think the contents were apple juice...

I don't believe this act would cause your back door to, uh, leak. But there may be some interesting corrosion within the engine.

Dan

As an edit: P.S. Would you, and possibly PTG, mind checking in on following thread? A pretty good guy is considering use of 36XL on a profile Cardinal. Sounds like a real good combination to me, but please note he is not interested in fitting engine with a pipe.

http://www.clstunt.com/htdocs/dcforum/DCForumID1/10995.html

Thanks,

This could be the trouble Dan. All this time I thought it was just poor quality bearings from Magnum.