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Cox Engine of The Month
August-2024
balogh's
![](https://i.servimg.com/u/f95/15/46/86/41/1_balo14.jpg)
"Cox TD09 R/C Beast of Burden featuring Kamtechnik head and DIY metallic fuel nipple"
![](https://i.servimg.com/u/f95/15/46/86/41/sponso12.png)
PAST WINNERS
balogh's
![](https://i.servimg.com/u/f95/15/46/86/41/1_balo14.jpg)
"Cox TD09 R/C Beast of Burden featuring Kamtechnik head and DIY metallic fuel nipple"
![](https://i.servimg.com/u/f95/15/46/86/41/sponso12.png)
PAST WINNERS
I would like to know how to date these Fox engines
Page 1 of 1
I would like to know how to date these Fox engines
Hello,
Here is a variety of Fox 35's, and one .15. How can I tell the age and correct designation for of these engines? I will be selling most or all of them and I would like to describe them and value them correctly. I know some of these engines are selling for only $10 or $15 dollars on EB. And some of my engines are not in great shape.
I would like to keep the .15 and find a strap muffler for it. The fact that there are no muffler screw holes suggest this is an older model. But I don't really know.
One is bright silver. I like that one too.
Is there a website that I could use to help in identification?
Thank you for any information you can share.
Bob![I would like to know how to date these Fox engines Img_1318](https://i.servimg.com/u/f62/20/55/18/43/img_1318.jpg)
![I would like to know how to date these Fox engines Img_1317](https://i.servimg.com/u/f62/20/55/18/43/img_1317.jpg)
Here is a variety of Fox 35's, and one .15. How can I tell the age and correct designation for of these engines? I will be selling most or all of them and I would like to describe them and value them correctly. I know some of these engines are selling for only $10 or $15 dollars on EB. And some of my engines are not in great shape.
I would like to keep the .15 and find a strap muffler for it. The fact that there are no muffler screw holes suggest this is an older model. But I don't really know.
One is bright silver. I like that one too.
Is there a website that I could use to help in identification?
Thank you for any information you can share.
Bob
![I would like to know how to date these Fox engines Img_1318](https://i.servimg.com/u/f62/20/55/18/43/img_1318.jpg)
![I would like to know how to date these Fox engines Img_1317](https://i.servimg.com/u/f62/20/55/18/43/img_1317.jpg)
robme- Moderate Poster
- Posts : 14
Join date : 2023-12-04
Location : Bedford Co. Va.
robme- Moderate Poster
- Posts : 14
Join date : 2023-12-04
Location : Bedford Co. Va.
robme- Moderate Poster
- Posts : 14
Join date : 2023-12-04
Location : Bedford Co. Va.
robme- Moderate Poster
- Posts : 14
Join date : 2023-12-04
Location : Bedford Co. Va.
robme- Moderate Poster
- Posts : 14
Join date : 2023-12-04
Location : Bedford Co. Va.
Re: I would like to know how to date these Fox engines
"I would like to know how to date these Fox engines"
I find that lying about how much I make helps...
The Smooth Mark
I find that lying about how much I make helps...
The Smooth Mark
batjac- Diamond Member
Posts : 2360
Join date : 2013-05-22
Age : 61
Location : Broken Arrow, OK, USA
Re: I would like to know how to date these Fox engines
The easiest identifier for the one engine is the red head. The first Fox Rocket was introduced in 1957. The following year the engine sported a black head and was now known as the first Combat Special. In 1959, this engine was introduced as a competitor for the Mccoy red heads and it was offered at a introduction price of $10.95. This lesser priced engine continuously dropped in cost as it was being assembled from inferior parts. You either received a piece of crap or a fairly decent running piece of crap. But, this is where you have to take the engine apart to check. Duke fell short of parts to assemble these engines. What he did was take Combat Special parts such as the crankshaft and the better conrod and placed it in the Red Head. I have examples of both. One runs and shakes badly while the other runs pretty satisfactory. http://foxmodelmotors.com/engines/36x/history.htm
This is from Bill Mohrbacher. I will find the other pages for the Stunt .35's. Some of Bill's dates may not match 100%. However, no one was more knowledgeable than Bill on the chronology of these engines. Bill knew Duke and many things were added later or changed early on. Bill was a member of this forum and sadly passed away a few years back.
Dating some of these engines can be highly inaccurate looking at them at a glance. You can get them pretty close. They were made for several years prior to minute changes.
All of the .35's you have pictured have a few modifications. I see some have Jim Lee Machine Shop venturi's. They have faux Tiger needles and another having a K&B needle. For the Fox purist, this could certainly impact your asking price. You have one engine in particular there that to me stands out. This is the middle engine with the white nylon venturi. It's not the engine that captures my attention. This engine was introduced in 1974 and for the most part is considered a giant turd. I'm a fan of these engines however whereas most aren't. They make decent power for what they are.
This is the Fox Sportster .36 engine. It was available in a .29 and a .36. If the lug has no number designation on it, it's a .36. This is a plain bushing .36 made from the Fox .36 MK 1 combat cylinders. it was supposed to be sold with the intent for slow plain bushed combat. Duke delivered on it too late, rules changed and he was now standing with his hands in his pants. Yours was a r/c version converted to control line. That being said, the muffler on that engine is worth more than the engine. You have a guaranteed $45 muffler there.
Here's some more info on the .35 stunt from Bill. http://foxmodelmotors.com/engines/35/35-history.htm One thing I will say in regards to your engines as I mentioned above, some of the parts are not factory Fox. While they may make the engine run superior to the Fox stuff, it matters to some people.
As far as your .15X is concerned, I would avoid using a strap muffler on ANY Fox as it will squash the cylinder out of round. The Fox .15X is very light because the crankcase is like a eggshell. Putting a strap on it usually results in deforming the case and cylinder which inherently places a bind in the piston sleeve. Fox did make a muffler for this engine, it was a real POS. It makes the engine overheat. The common mistake for this engine is that people try and swing a 8" prop on them. A BIG NO NO, this engine dislikes them severely and prefers a woodie 7x6 and run it like you stole it with nitro from 15%-20%. These can amazingly turn up.
This is from Bill Mohrbacher. I will find the other pages for the Stunt .35's. Some of Bill's dates may not match 100%. However, no one was more knowledgeable than Bill on the chronology of these engines. Bill knew Duke and many things were added later or changed early on. Bill was a member of this forum and sadly passed away a few years back.
Dating some of these engines can be highly inaccurate looking at them at a glance. You can get them pretty close. They were made for several years prior to minute changes.
All of the .35's you have pictured have a few modifications. I see some have Jim Lee Machine Shop venturi's. They have faux Tiger needles and another having a K&B needle. For the Fox purist, this could certainly impact your asking price. You have one engine in particular there that to me stands out. This is the middle engine with the white nylon venturi. It's not the engine that captures my attention. This engine was introduced in 1974 and for the most part is considered a giant turd. I'm a fan of these engines however whereas most aren't. They make decent power for what they are.
This is the Fox Sportster .36 engine. It was available in a .29 and a .36. If the lug has no number designation on it, it's a .36. This is a plain bushing .36 made from the Fox .36 MK 1 combat cylinders. it was supposed to be sold with the intent for slow plain bushed combat. Duke delivered on it too late, rules changed and he was now standing with his hands in his pants. Yours was a r/c version converted to control line. That being said, the muffler on that engine is worth more than the engine. You have a guaranteed $45 muffler there.
Here's some more info on the .35 stunt from Bill. http://foxmodelmotors.com/engines/35/35-history.htm One thing I will say in regards to your engines as I mentioned above, some of the parts are not factory Fox. While they may make the engine run superior to the Fox stuff, it matters to some people.
As far as your .15X is concerned, I would avoid using a strap muffler on ANY Fox as it will squash the cylinder out of round. The Fox .15X is very light because the crankcase is like a eggshell. Putting a strap on it usually results in deforming the case and cylinder which inherently places a bind in the piston sleeve. Fox did make a muffler for this engine, it was a real POS. It makes the engine overheat. The common mistake for this engine is that people try and swing a 8" prop on them. A BIG NO NO, this engine dislikes them severely and prefers a woodie 7x6 and run it like you stole it with nitro from 15%-20%. These can amazingly turn up.
Last edited by Ken Cook on Fri Mar 01, 2024 6:09 pm; edited 2 times in total
Ken Cook- Top Poster
- Posts : 5573
Join date : 2012-03-27
Location : pennsylvania
Re: I would like to know how to date these Fox engines
Ha ha Mark , I was thinking the same thingbatjac wrote:"I would like to know how to date these Fox engines"
I find that lying about how much I make helps...
The Smooth Mark
akjgardner- Diamond Member
Posts : 1554
Join date : 2014-12-28
Age : 65
Location : Greensberg Indiana
Re: I would like to know how to date these Fox engines
Thank you Ken.
That was very interesting.
What makes the muffler valuable?
That was very interesting.
What makes the muffler valuable?
robme- Moderate Poster
- Posts : 14
Join date : 2023-12-04
Location : Bedford Co. Va.
Re: I would like to know how to date these Fox engines
Fox has made several attempt at providing a proper working muffler. The blimp style muffler you depict in the upper left isn't correct for that engine. Let me restate that, it's the proper style but that version which is screwed together with the straight slotted screws wasn't made available until the late 90's. Fox did away with roll pins in the 80's. The blimp style buts up to the exhaust stack which is a crappy way of a connection. The small ears on the side of the crankcase are subjected to a lot of stress and they break off rendering them useless. The fix to this is to obtain 3/16" steel brake line tubing and cut two pieces which are measured from the back of the ear to the front of the stack. JB weld them up to the ear and to the side of the case. This prevents over tightening of the ears and supports the muffler slightly better.
The blimp style muffler usually falls apart. The roll pins would shake out and the tail end falls off. Keep in mind if one is flying control line and even a wheel falls off, your disqualified. Not only is it a penalty for the competition flyer, someone could get real hurt or other planes damaged in the pit if something like a muffler flies off. The exit of this muffler is far too small and needs to either have it's stinger cut off. I cut them off to enable a 1/2" opening. This keeps the back pressure from being too excessive. It also keeps the muffler out of the landing gear when mounted on a profile. So either you cut it off, or let the landing gear break it off for you. It's a easy choice to make. In a crash, the muffler WILL break the exhaust stack and it will destroy your fuel tank at the same time. This makes it double fun. Secondly, it breaks the ears off of the case which now can't be used any longer.
Now that I've explained some of the negatives of the blimp style, I will explain the positives of the middle Sportster series. The muffler itself is quite rare as it was made for less than 5 years. The front cap is machined aluminum, not cast. Your front cap is missing which seriously impacts the value of this muffler. Yours has a piece of wood epoxied into the front. The end cap was also held in with roll pins so they could've fallen out. Two styles of these front caps were made. One was short and the other long. In the situation of your engine, the front cap if not the correct version will extend into the prop swing area. Someone may have removed it so that it wouldn't strike the prop therefore plugging the muffler with a piece of wood for now. I generally install a aluminum spinner backplate minus the spinner which can pack the prop out enough to provide enough clearance for it to swing.
For me having a machined cap is a plus because I know it's not going to break. The muffler itself encapsulates the entire exhaust stack. This is not just a slip fit, it takes a bit of pressure to slip it on. This is a huge plus not only to prevent the engine from damage in the event of a crash, it assists in providing it from coming loose. If one is going to use a strap, THIS IS THE MUFFLER TO DO IT WITH ON A FOX. This muffler with a strap will interchange with older pre ear .35 stunts. The stack holds the muffler and strap will just retain it. The Fox .15 also had a muffler of similar stack design which would enable the use of a strap on the .15X. The problem is, it's hard to source and when it comes available, they go fast.
The exit of the stinger is slightly larger than the blimp style but it too requires opening up and I drill them out to the maximum I can achieve. This muffler utilizes 2 styles of attachment, the side ear style of attaching which is how yours is attached and the over and under screws which are in the crankcase itself. NEVER use the over and under screws unless it's your only option. These are through holes which have the cylinder liner directly behind them. If the screw touches the cylinder it will distort it and essentially ruin the engine. However, if one is careful, they can get by with using them but installing the screws is very tricky, at least for the one on the bottom.
This is quite a essay as to why the muffler is valuable but for others who aren't certain, it can be beneficial. I'm sorry for being long winded.
The blimp style muffler usually falls apart. The roll pins would shake out and the tail end falls off. Keep in mind if one is flying control line and even a wheel falls off, your disqualified. Not only is it a penalty for the competition flyer, someone could get real hurt or other planes damaged in the pit if something like a muffler flies off. The exit of this muffler is far too small and needs to either have it's stinger cut off. I cut them off to enable a 1/2" opening. This keeps the back pressure from being too excessive. It also keeps the muffler out of the landing gear when mounted on a profile. So either you cut it off, or let the landing gear break it off for you. It's a easy choice to make. In a crash, the muffler WILL break the exhaust stack and it will destroy your fuel tank at the same time. This makes it double fun. Secondly, it breaks the ears off of the case which now can't be used any longer.
Now that I've explained some of the negatives of the blimp style, I will explain the positives of the middle Sportster series. The muffler itself is quite rare as it was made for less than 5 years. The front cap is machined aluminum, not cast. Your front cap is missing which seriously impacts the value of this muffler. Yours has a piece of wood epoxied into the front. The end cap was also held in with roll pins so they could've fallen out. Two styles of these front caps were made. One was short and the other long. In the situation of your engine, the front cap if not the correct version will extend into the prop swing area. Someone may have removed it so that it wouldn't strike the prop therefore plugging the muffler with a piece of wood for now. I generally install a aluminum spinner backplate minus the spinner which can pack the prop out enough to provide enough clearance for it to swing.
For me having a machined cap is a plus because I know it's not going to break. The muffler itself encapsulates the entire exhaust stack. This is not just a slip fit, it takes a bit of pressure to slip it on. This is a huge plus not only to prevent the engine from damage in the event of a crash, it assists in providing it from coming loose. If one is going to use a strap, THIS IS THE MUFFLER TO DO IT WITH ON A FOX. This muffler with a strap will interchange with older pre ear .35 stunts. The stack holds the muffler and strap will just retain it. The Fox .15 also had a muffler of similar stack design which would enable the use of a strap on the .15X. The problem is, it's hard to source and when it comes available, they go fast.
The exit of the stinger is slightly larger than the blimp style but it too requires opening up and I drill them out to the maximum I can achieve. This muffler utilizes 2 styles of attachment, the side ear style of attaching which is how yours is attached and the over and under screws which are in the crankcase itself. NEVER use the over and under screws unless it's your only option. These are through holes which have the cylinder liner directly behind them. If the screw touches the cylinder it will distort it and essentially ruin the engine. However, if one is careful, they can get by with using them but installing the screws is very tricky, at least for the one on the bottom.
This is quite a essay as to why the muffler is valuable but for others who aren't certain, it can be beneficial. I'm sorry for being long winded.
Ken Cook- Top Poster
- Posts : 5573
Join date : 2012-03-27
Location : pennsylvania
Re: I would like to know how to date these Fox engines
akjgardner wrote:Ha ha Mark , I was thinking the same thingbatjac wrote:"I would like to know how to date these Fox engines"
I find that lying about how much I make helps...
The Smooth Mark
I was thinking of:
Gassing them up (those Foxes) with some booze, wait till they have enough to where they are lit (really drunk) and then let them go!
Just stay out of the way when you let them go because you'll never know what will happen?
Maybe you'll be able to a phone number from one and be able to date one of them?
We are talking about Glow engines? Sorry
![Shocked](https://2img.net/i/fa/i/smiles/icon_eek.gif)
![Smile](https://2img.net/i/fa/i/smiles/icon_smile.gif)
sosam117- Diamond Member
- Posts : 1318
Join date : 2016-03-23
Location : Suburb of Chicago, Illinois
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