FOX 36X Overheats

Gents, I've been running a good compression used 36x that was a good buy off of #bay. The problem I have is she seems to over heat with 1/4 tank or so left of gas??? Very hot to the touch.

Setup:
Gotcha Streak
Sull 4 oz. suction tank
Fox venturi insert stock NVA
Powermaster GMA 5/25
master 10-6 and spinner

Been launching slightly wet, starts to break great after a few laps, leans out a little then shuts down after 10-15 laps with gas left. Was a slight crack in one of the engine mount after last flight but no great vibration only slight. Crank looks great to the eye. Any info, parts motor or not, is appreciated!

Thanks robc in sd

robc,

I have a Fox 35X, dates to about 1964, runs great on Sig 10% nitro and 25% castor.

Your GMA fuel is probably ok at 25% castor.

My fear would be the rear needle bearing is bad...assuming the engine was broken in and the cylinder is not too tight.

Mine had been stored many years, 36 to be exact, but had been filled with motor oil...if you got this one off E-bay used, the bearing may or may not be ok...if one of the front mounting holes is now cracking, perhaps the bearing is overheating, expanding the crankcase so much in that area to the point of case failure.

I have no idea if the bearing is replaceable.

Maybe some of the engine experts can weigh in on this.

Where do you guys fly in SD?

The needle bearings are (were) available from the factory. I purchased several a short time ago to replace some on engines that I got off E-Bay. It is VERY difficult to get the old ones out of the case ans press the new ones in. You might be wise to contact Fox mfg to see if they will do the job for you. Contact Charlie Thacher at the factory.

Bigiron

Might there be a split or crack in a fuel line that is uncovered as the fuel burns off?

I would also be suspicious of the fuel tank. Also, there is no Powermaster 5-25 GMA. It is either 22% half n' half, or 29% all castor. I would use the 29% castor mostly because of the crank running directly in the aluminum at the front bearing. Is the engine broken-in? It may not have enough time on it. Steve

Sorry I mislead you guys with the crack (engine mount)!! It's on the plane NOT the motor. SORRY Mr. Steve Helmick, but I do run power master 5/25 GMA stock num 72099-00202 batch #2247 . Last of the GMA stuff?? I fly in Oceanside and at montgomery field in SD. Robc

LAST EDITED ON Jul-05-03 AT 09:33 PM (CDT)
 
>I would also be suspicious of the fuel tank. Also, there is
>no Powermaster 5-25 GMA. It is either 22% half n' half, or
>29% all castor.

Unless mislabelled atop the proper factory label at a hobby shop, Powermaster has ONLY produced two types of GMA-labelled fuel, EXACTLY as pointed out above. They told my dealer (Rebel Hobbies here) that they have dropped the 5% mix from one of the two GMA oil formulas, probably the 5 & 22 -- because they sold too little of it.

>I would use the 29% castor mostly because of the crank running
>directly in the aluminum at the front bearing.

That sentence looks wrong. There was a bushing in the ones that I have owned, I'm quite certain. But the 22% might not be oily enough, for the bushing, that much is true. The only one(s) I have now are late production, maybe they differ about the front bushing (the twin NB model was called the "Blue Ribbon" 36X).

> Is the engine broken-in? It may not have enough time on it.
> Steve .

Like most Foxes that old, it could take over an hour of repeated short runs and cool-downs to get the 36X's ready for steady running with a proper in-air prop (not a 10-6, normally -- 9-6's and 9-7's) instead of a break-in prop. To slow it down if it's too fast in the air, try a lower pitch, with which a 10" is OK, like an APC 10-5.

Kiwi

I assume you have one of the early '70s era.36Xs? These share nothing but the Fox name and displacement with the earlier needle bearing .35X/.36X and .36XBB series. This seems to have been a time of spotty QC at Fox from what I have gathered. The period's .36 Schnuerle Combat Special was sure nothing to write home about (reknowned for having the front half of the crank come flying out of the motor) and it seems some of the rest of the line suffered some as well. If your's is anything like the specimens I have had- it will take two gallons of fuel just to get it where it will run decently and not overheat. I suspect it is fitted WAY too tight once it gets up to operating temp. Mine was still smoking when carried back to the flite box area, until I finally got it sorta "run in".

GOOD LUCK!

I had a recent experience that may be of benefit. An OSLA25 running fine on the ground, in the air for a few laps then anemic, surge, anemic, surge run to the end of the tank. The old style OS needle valve assy was the culprit. Replaced with a ST needle valve solved the problem set the run just inside of the two cycle gave top power runs for the full tank. SOOO

You mentioned the stock needle valve assy. May I suggest you get rid of that for the ST assembly. Most guys do it with new motors right out of the box. Just a thought to consider. Of course the above comments are something to also consider however, this suggestion just might be the cure without entering your motor.

In my outboard hydro racing days in the 50's we had a fella with a KG4 Mercury Hurricane (15 cubic inch displacement) that he never took apart for ten years. It rattled like a sewing machine, screamed like a siren, but had fantastic power. It was loose as a goose but with a borrowed hot prop from another well known racer, a straight cometitive three point hydro and my light weight; we were within fractions of breaking the world record but unfortunately I finished 2nd and the leader did establish a new record. Lesson learned here was if the power head is well set up, do not break into it. He only used it for record attempts. The motor belonged to Larry Knight of Seattle. The prop was borrowed from Mike Jones a current or recent unlimited hydroplane driver of Seattle.

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler

>I had a recent experience that may be of benefit. An OSLA25
>running fine on the ground, in the air for a few laps then
>anemic, surge, anemic, surge run to the end of the tank.
>The old style OS needle valve assy was the culprit.
>Replaced with a ST needle valve solved the problem set the
>run just inside of the two cycle gave top power runs for the
>full tank. SOOO
>
>You mentioned the stock needle valve assy. May I suggest
>you get rid of that for the ST assembly. Most guys do it
>with new motors right out of the box. Just a thought to
>consider. Of course the above comments are something to
>also consider however, this suggestion just might be the
>cure without entering your motor.
>
>In my outboard hydro racing days in the 50's we had a fella
>with a KG4 Mercury Hurricane (15 cubic inch displacement)
>that he never took apart for ten years. It rattled like a
>sewing machine, screamed like a siren, but had fantastic
>power. It was loose as a goose but with a borrowed hot prop
>from another well known racer, a straight cometitive three
>point hydro and my light weight; we were within fractions
>of breaking the world record but unfortunately I finished
>2nd and the leader did establish a new record. Lesson
>learned here was if the power head is well set up, do not
>break into it. He only used it for record attempts. The
>motor belonged to Larry Knight of Seattle. The prop was
>borrowed from Mike Jones a current or recent unlimited
>hydroplane driver of Seattle.
>
>Bob Smiley
>A Lancair 360 builder/pilot trying to be a modeler

I always thought hydroplanes were way cool!

John,

Hydros were cool. A great experience for a young teenager in the 50's in the Pacific Northwest when the Slo Mos were king screaming under the Lake Washington bridge at 160 mph with the Allisons and supercharged Rolls Merlins roaring down the chute and names like Joe Taggert and Lou Fagel were revered. Learned a lot, met a lot of great guys, many of which went on to break records, develop new ideas in outboarding and step up into the big time boat racing as the years went by. Lessons in that arena are transferable to other areas of life.

It was at one of the Gold Cup races when the new Boeing 707 or 727 (can't remember which) made a one G barrel roll over the course and sales jumped for Boeing?

Bob Smiley
A Lancair 360 builder/pilot trying to be a modeler

>It was at one of the Gold Cup races when the new Boeing 707
>or 727 (can't remember which) made a one G barrel roll over
>the course and sales jumped for Boeing?

That was the prototype Boeing 707. The barrel roll was executed to subject the airframe to exactly 1 G. The test pilot had to explain himself to the managers afterwards..

>That was the prototype Boeing 707. The barrel roll was
>executed to subject the airframe to exactly 1 G.

I used to belong to a free flight club that met in the AA training buildings here in Dallas. We had a copy of a piece of movie film that was taken from inside the plane during the roll. Before it was shown a group of new pilots for AA was brought in by their instructor. After the film they were told "I never want to hear of you doing that". I had seen a photo of a single frame of the movie but had never seen the movie clip before or after. Way cool!

I used to like painting with dope but now I can't remember why

A little more insight on that 707 barrel roll. I was on the tarmac in Bremerton, Wa.last summer; two fellas came in in a Cessna 202 and one of the guys told me that his buddy was the co-pilot on that 707 ride. We had a conversation and he revealed the following information.

The next day, after the incident, a high boeing official was hopping mad. He may have been the president. He royally chewed out the pilot, put him on suspension and within a few days later there were 20 orders for the 707. The pilot was reinstated. I asked him where he was on that day. His reply was, "I skipped out of town to eastern washington to avoid the heat."

Thought you might like "The rest of the story. Goodday!!"

Guys,

I have the engine and the MAN article, there is a rear needle bearing, NO front bearing in the Fox 35X/36X circa 1964/65.

The front of the crank runs in the case...according the reports, I could take the prop of my engine and check, but I am a little too toasted this evening to perform that act.

If you are REALLY running at least 25% preferrably 29% castor, I would worry about the rear needle bearing, otherwise, get some 29% castor...with the correct
fuel...all things being honky-dorry...it should cool-off and run.

I run these a lot. I have one 36X with needles on both ends. The rest have needles on just the rear. I changed the rear bearing on one of my better 36xers. What a pain. I dont suggest it. I think that I have a spare new bearing but all of the ones that I have clean up pretty nice with a tooth brush and some ATF or the marvel stuff. Polish the crank till it shines with 600 or finer.Clean the goo off of the piston/liner set. AND clean the outside of the jug!!! maybe add a head shim/gasket(same as Stunt 35)
RE; hot run. Try a bladder to eliminate the leaning of the tank and try some more castor added to the fuel. A flatter pitch prop will lessen the heat also until the engine is more broke in.
My first guess is that the venturi hole is too large for the fuel draw to be even thru the tank run. I dont even try to run these on tanks anymore, just bladders now.
They sound great with a 9x7... MM

LAST EDITED ON Jul-05-03 AT 06:29 AM (CDT)
 
The '70s era ".36X" is a bronze bushing motor. I always preferred the earlier "real" .36Xs (like the NBs you have) myself . Some people have had decent success with the later type but I'm not one of them. They generally tend to vibrate quite a bit too. If you can get a good one it's a decent non-schnuerle plain bearing .36 sport motor. Some guys tried using these in Profile Carrier, Slow Rat, Slow Combat- back when they first came out, and the C.35 Tigres just chewed them right up...

I'd switch to a bladder or uniflow tank.

These engines can get really hot. One of my fondest memories is of crashing one of Phil Granderson's .36X-powered combat planes. (The control horn broke; it wasn't my fault.) The pacifier broke, the fuel hit the engine, and the airplane burst into flames.

Same fire thing happened to me, The club saftey guy looked on as i ran to get a "fire extiniusher" cam e back with the camera and took a pic. I had dragged a dirt circle around it so that t wouldnt spread, too far... Boy, foam burns fast and complete.
MM

You aren't kidding!

LAST EDITED ON Jul-05-03 AT 01:59 PM (CDT)
 
>The '70s era ".36X" is a bronze bushing motor. I always preferred the
>earlier "real" .36Xs (like the NBs you have) myself .

There was a gap in Fox 36 production about the time the Mark II, which was labelled 36X on its bypass, and the Chrome-shiny Sport 36 were not yet in the stores. Duke claimed later that he had been promised by a few influential combat folks that the official AMA Slow Combat rules were going to specify a plain bearing engine. The first few of the Shiny Shakers were sold in 36X boxes, with a sticker over the "36X" label, but were never CALLED 36X's.

>Some people have had decent success with the later type but I'm not
>one of them. They generally tend to vibrate quite a bit too. If you
>can get a good one it's a decent non- schnuerle plain bearing .36
>sport motor. Some guys tried using these in Profile Carrier, Slow
>Rat, Slow Combat- back when they first came out, and the C.35 Tigres
>just chewed them right up...
>
The Tomcek brothers used Sport 36's often in AMA Slow when they and the event were both still new. The piston and sleeve were supposed to be the same as the 36X, and when the matte (or "Satin"?) -finish version came along, it reverted to the original type of 36X head, instead of the unusual tapered- fins head. I now own a Black Head Fox, which I haven't run yet. Never had one back in the 1950's; GMA always claimed the the BH was the worst- vibrating Fox of all time. My own experience has been that the Sport 36 was the worst in that regard that I ever tried.

.
Kiwi

Here's the link to Powermaster's page with the GMA mix options. I have not been able to get 15% GMA into our LHS as the distributor doesn't stock it. And I have not been able to confirm that any of the %5 nitro GMA mixes have been discontinued, but very possible that a local distributor stopped stocking it. Mislabelling is not at all out of the question. http://www.powermasterfuels.com/control.htm

I also think you have too much prop on the engine. Depending on the speed you desire, consider a 9-6, 10-5 or even an 11-3 (APC makes one). Rule of thumb: Set speed with pitch and rpm with prop diameter. Steve

The label is a factory label with bar code and such. The fuel might be (old) stock. Was a x-mass present bought from a LHS in the LA area. I sent an email to power master to justify the batch num with the mix 5/25. We will see. Thanks to all who answered! RC

Here is a pretty good web site with historical information on the fox combat engines.

http://www.clcombat.info/foxhistory.html