Sport_Pilot

Not a stock LA. With an 8x4 the LA gets almost 1,000 RPM less. Also if you want speed I would go with a 7x6 prop. I believe this engine does best between 14,000 and 15,000. But also with a heavy iron piston it might be better for longevity to rev a bit slower.

RV Winkle

Does anyone have a source for substitute glow heads? Not plugs. I have a Fox 07 rc that I would like to use but only have the original (new) glow head.

thanks

earlwb

The glow heads show up from time to time on the big auction site and other locations. Right now the .049, .07. and .09 etc glow heads are in someone's storage location. They used to sell the parts via Virgina Hobbies, but they closed up shop. Since then no one that I know of has continued to sell the engines or parts from that stockpile.

I plan on milling out the post and drilling and tapping a bad head for a 1/4x32 glow plug and use that instead. Another thought it to machine the bad glow head to take a turbo plug too. But my glow heads are still working just fine, so I haven't pursued it yet. I'll be more motivated when I have a couple three heads lose their glow elements.

RV Winkle

Thanks for the info

hsukaria

Posts #1545-1551 have helpful information about the Fox 1/2A engines/glowheads.

50+AirYears

Since burning up a couple old engines using straight synthetic oil fuel, and since most of my engines could probably be considered old, I have been using mostly Omega 10%, with roughly 6 ounces of castor added per gallon. I have an Eagle III on a Super Sportster 60 that I've been flying roughly 12 years with this engine, well over 100 flights. The Summer of 2012 was the first time in all that time I was able to use my Sulivan HD starter to get it running the first try of a day. Previously, apparently while the engine was still breaking in, I usually had to use a screwdriver handle as a chicken stick. Nobody else's starter did any better. In fact, the first 10 or 15 flights, the starter was totally useless for this engine. That summer was also the first time in the history of the plane that I was able to run out full 16 ounce tanks. I've been anxious to try it again this year, but we moved South, and first have to find a workshop with an attached house so I can unpack my fleet from a storage unit and get back to building. So far this year, most of my flying has been rather limited to my Island Hopper, a small gyro stabilized mini heli, and a Sky Viper heliquad that I've at least had the fun of using to try to teach flying to my 6 year old granddaughter.

hsukaria

This subject has likely been discussed here previously, but I have been having a heck of a time keeping my glow plugs from blowing seals on my bigger engines. At first, I suspected that the Fox 74 Eagle IV I have is running too hot and lean. But then I purchased another engine (an SK90) for another plane and installed the same glowplug on it. It also has been blowing the plug seals. The plugs I have been using are Fox #8. I lost an airplane last week because the engine (Fox 74) quit on takeoff and I didn't have enough speed or altitude to save it. I had just had a great flight with the same setup and settings a few minutes earlier but then on the second flight, the plug seal blew.
After mentioning this to another guy at the field, he said he experienced the same problem with some Fox #8 plugs and switched to some other plug and put the Fox #8 on his smaller .40 c.i. engines with good results. I investigated my smaller planes and see now that the Fox #8 plugs have been running well on the smaller engines but keep blowing seals on the 74 and 90's.
Has anybody else experienced that? What would be some good choices for glowplugs for my Fox 74? I have OS #8 plugs that I will try on it. Otherwise, the engine runs great.
I have been using 5% nitro fuel with some castor added to the fuel and a 12x6 XOAR prop and MVVS stock muffler (not tuned, similar performance to Fox stock mufflers but not tilted).

aspeed

I would try a different brand of plug. I have a bunch of Fireball plugs that blow the seal too, especially when I pull out shims to go faster. You could add a shim and see if that helps too. One motor I have is bad for the seals and elements, and I just added a shim and all is good now.

hsukaria

Yep, I just recently added 2 head shims that I purchased from Fox. The engine still runs nice, but I suspect that lately my problems have been with the glowplugs.

landeck

My Feedback: (1)

I am having the same problems with a 74 I bought two years ago mounted in an Escapade 60. I first ran it on the bench for two tanks and the flew it for six flights very rich. I noticed the engine did seem rather hot after each run. I was using a Fox standard RC long plug an Omega 10% fuel. I leaned it out a little and the engine died after about two minutes into the flight. The engine was very hot and the seal on the plug was blown. For the rest of the summer the same thing happened on every flight. The engine seem fine on the ground but would over heat in the air and die. About 1 out 3 times the plug seal would be blown. I changed fuel to 5% Sig Champion; tried a Fox #8 plug, checked and redid the fuel lines and tank; tried a APC 13x6 prop instead of a 12x7 prop; nothing helped. Then the middled of last summer I switch out the Fox for an OS 75 AX without making a single change to the fuel system or plane. The OS has run perfectly now for 20 flights. Therefore the problem has to be with the engine. I talked to Fox and they had no idea what could be wrong and asked that I return to them for a check up which I will do.

Bruce

hsukaria

Hi Bruce, keep us posted with your findings from Fox. I also discussed the same thing with them and they suggested that I send it in. But before I sent it back, I added 2 head shims (I also switched to their latest head button). But the glow plugs still blow. I will try another brand of plug. If that fails, I will ship it back to Fox for investigation.
I also get the engine to run well on the bench, but quits in flight, even though I think that I am running on the rich side.

Sport_Pilot

The Fox #8 is a very cold plug! If you are using it to cheat on the nitro. (IE using more than the Fox .74 would usually handle), then that may raise pressure. I would think with low nitro you would be using the Fox RC or the Fox Gold plug. Also way too cold for your smaller engines unless you are running a lot of nitro.

Sport_Pilot

You ran too much nitro for a Fox .74. They were designed for no nitro at all. You can use 5% most of the time, but not in real hot weather. Run it with no nitro and it will out run the OS with 10% nitro.

hsukaria

I might try 0 nitro later. I have been running 5% nitro with the new head button plus 2 head shims. I would have guessed that the new head button with 2 extra head shims would allow the use of 5% nitro. I will try a different plug, if that doesn't work, I will get some 0% nitro. I used 0% previously, but at that time I was still using the old head button and no shims. I still had Fox #8 plugs blowing with that setup. But it may be from these specific glowplugs since I was using other glowplugs originally on 0 nitro and not blowing the plugs.

Sport_Pilot

Sorry I was replying to Landeck's post.

siberianhusky

Cool thread! I have a late 60's early 70's 35 c/l stunt NIB, original plug still in it along with the muffler, never been run!
No it's not for sale, part of my small collection of vintage engines.

landeck

My Feedback: (1)

Please reread what I wrote. I started with Omega 10% nitro because that is what the tech at Fox said that they test the current 74s with. The current version has a new head button and carb compared to earlier versions. Also I used the Fox Standard RC long plug. Results were blown seals on plugs and engine over heating. Next I tried Sig Champion 5% nitro. No change in results. Next I tried a Fox #8 plug with the 5% fuel with no change in results. I tried different size props to lower the load on the engine with no change in results. I replaced all fuel tubing with no change in results. That is why Fox requested that I send it to them.

Sport, do you own a current version of the Fox 74 or any version? Where do you fly here on the north side of Atlanta?

Bruce

hsukaria

Landeck,
do you know if your Fox 74 has any head shims added? I went through that excercise a while back and realized that the head clearance was way too low, even with the newest head shim retrofitted. The Fox technician said they add head shims to their engines now. I added 2 on mine, but did not test if 1 would have been enough. Regardless, I still blew plug seals on it with 5% nitro, reduced load (smaller prop), new head button and 2 shims. Did you try different brand plugs on your 74?

jeffie8696

I was told by Aldon Kelly of Merlin Plugs that blowing plugs is a sign of overcompression. I use his plugs exclusively with good results. And he is just a heckuva nice guy.

landeck

My Feedback: (1)

Huskaria, I have not checked the head shims on my engine and I have only used Fox plugs on this engine since they along with OS plugs always have worked fine for me. I think I am going to let Fox figure out if additional shims are needed.

Bruce

Sport_Pilot

I do not have a Fox. 74, but do have an older Fox .50 and they said if ran well on 15%, but that was a lie. It does not like more than 5%. But it will run well on 10% in the winter. Blowing plug seals is common with detonation.

I have not flown much since about 2005 or shortly after my kids were in high school. With college bills I cannot afford this hobby, last flew almost two years ago at Cobb County RC.

hsukaria

After your kids finish college, send them a bill for all the flying time missed!!!

hsukaria

Bruce, if Fox Manuf. explain to you what they did to fix your engine, it would be helpful to the rest of us if you let us know what they said.

landeck

My Feedback: (1)

Will do.

Bruce

1QwkSport2.5r

I have the opportunity to acquire a Fox 1.20 twin glow engine and mount. It is unrun but no mufflers and possibly no box. It has the original Fox Carburetors too. What is a realistic price in today's market for this engine and how high on the collectors scale is it? It's not real common, I know that.