Fox 35 collectors edition

Hope you can see the crankshaft from picture
And there is no restricted I can see the crankshaft is there any aftermarket I can use ?
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Yes the back plate is not drilled. That would require a pressure fitting correct?  I don’t have that either

Don't drill the backplate. I just checked my red heads and the venturi's on both WITHOUT the restrictor is .297". I checked my "57" Rocket and it also is .297". My "58" Blackhead is .312" with the restrictor in the venturi. The Blackhead still runs fine on suction. I have the stock needle valve assemblies on all of them. The needle is the Fox "Spade" type needle. These were the assemblies used on the .35 and .36X cases.  However, a needle which I prefer is the Fox .40 assembly. The Fox .40 as I call it was used on the .40's but it was also used on the later MK series IV and exclusively on the MK V. To distinquish this particular needle valve assembly it utilizes a very large knob. These needles not only work, they work with bladder pressure if desired.

      I see in your pictures that your crank web is the full circular crank. I wouldn't be concerned as to what crank is in there. I was just mentioning that the engine while on the outside appears the same, there are differences in these. One does indeed shake more than the other and I have both but I can't recall which is which without running them.  The engine was introduced to be a entry level engine to compete with the Mccoy Red head. Sometimes these could be very hit or miss in terms of quality and run quality. These engines were offered for around $10. One thing to also note, these engines use a brass end pad which wear out fairly quickly exposing the wrist pin to the cylinder liner. I know of no replacement of these brass rivets pressed into the wrist pin. This is one reason I strongly dislike old Fox's. A crappy design that can ruin the engine quickly. I certainly prefer the circlips used on the later Fox's assuming they stay in place.

Thanks now to find a fox 40 NVA

Diagnosing issues over the internet is a crack pot guess at that. I'm still not certain as to why your having problems with the engine run because the Fox .35 stunt needle should still be working. I go on and on about what I prefer and what I use for some of these engines. Every Fox needle valve is questionable. Just because it works in one engine doesn't even mean the same needle works in another because the fits and finish of all the spraybars and needles are lacking. It all comes down to air leaks. You must stop the air leaking. Knowing if your venturi stack is modified would help if you were able to measure it.

                   I don't know what you were making reference to when you said rich or lean. Which one was it? If the engine is running erratic going rich to lean, this is more than likely that the engine is receiving adequate fuel and then it's not going lean. Generally, it means there's a problem. However, the same issues occur when a engine is vibrating and the fuel is foaming. It can also happen if the plug is bad or possibly on it's way out. Other issues occur when the engine is coked up with castor varnish especially at TDC and this is causing a bind in the engine which leads to excessive heat and it robs a lot of power causing the engines to run erratic. This kind of issue can also destroy the engine.

         I provided a picture here of the stock needle valve for the Rocket .35 and the .Fox .40 needle as I reference it.        
           Stock is on the left and the .40 on the right

       The stock spraybar throat diameter is .140" whereas the .40 size spraybar is .162". The stunt .35 needle can vary from .127"- .130". The stunt .35 spraybar would offer the most power to this engine. The difference though between the stunt .35 and stock Rocket version would be almost non detectable but you would see a power loss using the .40 size but with probably a broader needle setting due to increasing fuel draw. When needed, I do a few things such as turn down the center cross section or file two flats on the throat area where the spraybar is exposed inside the venturi.

           What fuel are you using in the engine? I prefer all castor in these 50's style Fox's due to the wrist pin issue I mentioned above.


                If your confident you have no air leaks, put the engine on the stand and choke down the venturi. This can be done numerous ways. Jam a piece of fuel tubing into the venturi and let it breathe through the hole of the tubing. Obviously this is just a test. See if the engine calms down. I've even used balsa sticks letting it rest on the spraybar and blocking half of the venturi. Your just determining if the engine's venturi is too large for proper fuel draw.

I also wanted to mention something, seeing that you have the backplate off, it's a good idea to lap the mating surface of the case on a piece of glass with a piece of 400 sandpaper and oil. After I get the back of the case flat, I do the backplate. I cut a piece of sandpaper about 1/2" larger than the backplate, I cut a circle in the paper so the paper can go over the backplate. I glue the paper to the crankcase grit side out and I can then lap the backplate to the case. This insures a perfect seal on the case to backplate.

Thanks Ken
Yea later today I am going to give it another go. I put a new plug in yesterday and changed the NVA to the ST that helped but still runs rich / lean. What I mean by that it runs fast then slow runs fast then slows. I also took off fuel tank and gave that a clean out. The engine is  not gummed up. As far as measuring the Ventura? Im not seeing anything down in there as you would on a combat special. One it starts today I will attempt to block off Ventura and see what that does and I am go to watch for bubbles in my air line. I will post progress thanks Ken
Fuel 29 castor 5% nitro. Little warm today 90,s
Going to wait till it cools down some. Also the back plt I did Lapp the case and when I had it off the screws were a little stripped so I didn’t tighten them down that tight and that back plate where the pressure fitting is I noticed there’s a flat spot on the inside does that go towards the top or towards the bottom? I am going to pull back plt off again add another gasket and new Screws

Also I’m going to put stock NVA back in

The flat which is located on the round portion of the backplate would go facing up. This is for clearance of the bottom of the piston skirt at BDC. Are you running the engine on a plane or a test stand? Regardless, this sounds like a vibration issue to me. I also know factually that this engine is a shaker. I generally put a spritz or two of original formula Armor All in my fuel jug. I've been doing this for nearly 20 years. The outside peanut gallery will tell you that this practice ruins the glow plugs. I can only suggest what I know works. if you have a clear jug of fuel, shake it up and look at the foam it produces. Put a spritz in the jug and shake it again and this will show you it works You have people that will tell you how to do something and people that actually do it. Use your best judgement.

Ok I came to the conclusion it’s to hot lol. But I switched some NVA around and this is what I came up with. It seems that to try to get a lean setting on the rocket isn’t going to happen. I’m Meagan it’s not as lean as I can get with a fix 35 stunt, maybe there just that way or like you said can hit or miss. I did notice when I took apart to clean it under the head it had about 4 metal shims, I only used one when I put it back together maybe the head is warped??  
It did run better then before adding the fuel line to the NV I was just being lazy and didn’t add it the first time. I took the ST NVA out can’t see wasting that NVA on something I just want to turn around and resell. I believe it has the stock NVA now if I understood you.
Couple more questions what color red did fox use?  And this is the kicker. What case , is it the same as the 36 or 35 stunt can I use a head from a stunt 35?? Maybe it’s sucking air there since the original owner had so many shims.
But pretty cool it’s running better it’s just got to run on the lean side. I should have checked rpm’s maybe next time to hot now.
Thanks
Ken

This is a rocket on eBay now
I would like to have but a little pricey for me

You bring to the table some of the points I was making above. Fox needle valve and spraybar assemblies are absolute crap. Therefore, your notations of poor, good, best confirm what I'm mentioning. You can interchange all of those needles within another spraybar and get absolutely different results then what you already noted.  Duke was cheap, he more than likely received 3-48's from surplus war supplies at a basement bargain cost which is why he used them so much. His thread cutting blows and many times needle valves are practically falling out of the spraybar.

         The Rocket case was only made in a .35. The reality though is that the diameter of a .36x liner is identical to every .35 that Fox offered. He changed the stroke and thinned the top of the liner. Therefore a .35 stunt will fit the Rocket case and vice versa. The .36X wasn't offered until 1964. Later MK series .36's beginning with the MK3 were completely different and won't interchange with the earlier cases. In 1961 the engine had the Rocket designation on the case but the engine was called the "61 Special". It featured a bolt on front end with dual needle bearings, this was the first bearing raced  Combat Special.

       What did change internally was the shaft diameter and the size of the crankpin.


           Why you have so many head shims could be a variation of issues. The Red Head was a engine of throw together crap parts Duke had lying around. The notation you show of Duke putting in Combat Special parts confirms the differences in my two examples which is why I said there were two different crankshafts. I own both and I can't remember which one was the smoother runner.

             Duke also added head shims to certain engines to assist in initial break in such as the Fox .15X. The Red Head Rocket though was a conglomeration of mismatched parts he was just trying to get rid of. Sometimes the baffle could strike the head and he possibly wanted to avoid this by adding more head shims.  There's no rhyme or reason to anything he did, he did whatever. Of course I'm just speculating here but I have encountered the baffle striking the head and the head gaskets were the solution.  JUST MAKE CERTAIN THE HEAD ISN'T BOTTOMING ON THE TOP OF THE  CASE. That could be another reason for the gaskets. This way your actually tightening the head to the liner and not the head to the case.

              The current cost of this engine on EBAY is a premier example of idiots. Why someone would even remotely pay that kind of money for what is a would be crap engine is beyond my thinking.  The "58" Blackhead is a better engine and it runs superior to the Rocket. In addition, I've found the Rocket cases to wear extremely and I believe it's due to the severely out of balance crankshaft.

It’s all starting to make sense now. Good point on tightening the head to liner not the case I like that thank you once again Ken your knowledge blows me away thanks

Ken Cook wrote:
I see in your pictures that your crank web is the full circular crank. I wouldn't be concerned as to what crank is in there. I was just mentioning that the engine while on the outside appears the same, there are differences in these. One does indeed shake more than the other and I have both but I can't recall which is which without running them.  The engine was introduced to be a entry level engine to compete with the Mccoy Red head. Sometimes these could be very hit or miss in terms of quality and run quality. These engines were offered for around $10. One thing to also note, these engines use a brass end pad which wear out fairly quickly exposing the wrist pin to the cylinder liner. I know of no replacement of these brass rivets pressed into the wrist pin. This is one reason I strongly dislike old Fox's. A crappy design that can ruin the engine quickly. I certainly prefer the circlips used on the later Fox's assuming they stay in place.

Ken,
The McCoys have a similar problem but theirs is on the end of the crankshaft.
You could do the same thing as I do and make the small rivet from Teflon?

Below are photos of how I rebuilt my McCoy engine with a new Teflon rivet.
Replacing the older on that got worn out.
By the way, MECOA doesn't have the part in stock anymore (for years).

I get the pistion sleave out after heating in oven at 165 some but then it just won’t come out anymore. Somethime s I get lucky and can pull it out 50/50 but other times not. What do you guys grap the sleave with ? I made the mistake to grab it with channel locks from the top of the sleave but must have bent it because I could not get it back together. So if if it just won’t pull out by hand I leave it be. But now I’m curious what shaft I have also.

I see in your pictures that your crank web is the full circular crank. I wouldn't be concerned as to what crank is in there. I was just mentioning that the engine while on the outside appears the same, there are differences in these. One does indeed shake more than the other and I have both but I can't recall which is which without running them. The engine was introduced to be a entry level engine to compete with the Mccoy Red head. Sometimes these could be very hit or miss in terms of quality and run quality. These engines were offered for around $10. One thing to also note, these engines use a brass end pad which wear out fairly quickly exposing the wrist pin to the cylinder liner. I know of no replacement of these brass rivets pressed into the wrist pin. This is one reason I strongly dislike old Fox's. A crappy design that can ruin the engine quickly. I certainly prefer the circlips used on the later Fox's assuming they stay in place.


Ok I got a sleave out of one of the rockets but now having a hard time getting pistion ron of pin on crank. I notice on this crank a ledge under the pin on crank that I never noticed on a 35 stunt. ??? Any help on determining what crank ?

You have bigger problems than what you think. If there's no need to take it apart, DON'T. See the hole in the crankcase on the back about a half of a inch above the backplate area? First you need to remove the liner, constantly heating with a heat gun and penetrating oil. Get it to move up and down and then from the bottom through the back of the case push the liner up with a block of wood. I use maple motor mount stock. Remove liner, the piston and rod won't come out like a Stunt .35. You have to remove the wrist pin through that hole in the case. If there's varnish on the wrist pin it's a real pain in the neck.I can sometimes screw a drywall screw into the center of the wrist pin bushing and withdrawl the wrist pin. The piston won't come out of this engine any other way. You don't have the Combat Special crank, you have the full circular web version which is milder timing. In addition, the pictures above which show the Teflon wrist pin pad on the Mccoy, this doesn't and will not work with a Fox. The conrods on Fox's are slightly wider than the pin itself. Therefore, the rod hits the backplate and not the pin.

Well a day late and a dollar short I got the sleave out but that’s as far as I’m going with it hopefully I can get the wrist pin sleave to slide back down over pistion. Fingers crossed.
Even the head look different then the 35 the grove for baffle look bigger. Going to clean and put back together after paint drys on the heads

Well a day late and a dollar short I got the sleave out but that’s as far as I’m going with it hopefully I can get the wrist pin sleave to slide back down over pistion. Fingers crossed.
Even the head look different then the 35 the grove for baffle look bigger. Going to clean and put back together after paint drys on the heads

So does this
Mean I got a bad rocket ? I guess the one before the hybrid???

Got the sleave and pistion back in

I just noticed I have 2 different style cases ??

The second one the one you said don’t tear apart is a 1959 a 29 case no wrist pin nothing special. The first one I never got the sleave out is as far as I can tell a 1960. Unsure of case and crank but it does run that’s the first one I was fooling with. Again thanks for everyone s help greatly appreciated I think I got it straight on the rockets. It would be nice to know what case and crank I have in the first one.

In general, any engine that has that hole on the case is not a good idea to take apart unless needed. Super Tiger uses that hole on many engines as well as others. K&B uses a plug to fill in that hole. Reason being is that you can damage the end pad of the wrist pin. The brass end pads are susceptible of damage on the Fox, they're paper thin.
The round case is essentially the Combat Special case derived from the Blackhead. There's probably more to it in terms of the Rocket logo. The squarish case is the forerunner to the ball bearing "61 Special" which is essentially the same case but the front end bolts on.

This is from Bill Mohrbacher. My son and I really miss Bill. With Brodak's going on this week, Bill was always there with his displays of engines. He's truly missed.
http://foxmodelmotors.com/engines/36x/history.htm

I wish I could have spent time with him and picked his brain. I heard he was a tremendous help to Duke. Thanks for the link. I printed the article out and added to my overflowing notebook.
I am
Send 2 pictures of NV,s one is the whole assembly and one is just the needle. Can you in lighten me please on the 2

The needle assembly you show appears to be what I describe as the Fox .40 needle. The knob is exceptionally larger than the Stunt 35. These assemblies are generally only in a black finish. I do have some in a different finish but they were a aftermarket replacement. Your missing the ratchet clip which is essential and specific to this assembly as it's larger. Other ratchet clips won't work without modification. The single needle valve assembly I believe was used in the Fox .40 Schneurle case engines as it states low speed indicating r/c carb which I believe is the MK Fox carb. Other engines as well like the Fox wart .40 and .45 more than likely shared the similar needle.