Is this the 'Pinch" i have read about elsewhere. I have never felt this in my Fox 35s, Cox 049s and new to me OS engines. This engine has never had fuel in it. I just put a prop on it to get some runs since I have just acquired this engine recently. I really don't want to unnecessarily break it down. Might get better with some Marvel or fuel. Just asking before  I go any farther. Thanks in advance!

Quote from: Roy Lane on March 02, 2026, 09:33:34 AMIs this the 'Pinch" i have read about elsewhere. I have never felt this in my Fox 35s, Cox 049s and new to me OS engines. This engine has never had fuel in it. I just put a prop on it to get some runs since I have just acquired this engine recently. I really don't want to unnecessarily break it down. Might get better with some Marvel or fuel. Just asking before  I go any farther. Thanks in advance!

   If you turn it over at low speed (like by hand) or worse, with the glow plug out, it is supposed to bind/squeak when cold. The top of the cylinder expands when it is running to a proper fit.  DO NOT use Marvel Mystery Oil or anything like it. If you absolutely must put oil in it, only tiny amounts and as thin as you can get it. '
 
   My suggestion is to just run it on *recommended* fuel. No Fox Superfuel, Powermaster GMA, or any high-castor content fuel.

    Brett

  That pinch is normal. It confuses many people that he never had an engine that was built to such close tolerances. The piston is aluminum and the cylinder is ceramic coated inside and outside. That is what helps make for the tight fit. The more recent instructions tell you to remove the head  put a few drops of fuel in the cylinder, and spin the prop with the spring starter and repeat numerous time. This laps the piston to the cylinder. Flush the cylinder out now and then. It will stick a lit at first, but eventually will get easier. We used Norvel .061s at KidVenture for years. To speed up that process, we used an electric starter to bump the engine with, just for a second or two at a time, and flush each time. Don't over do it. Put the head back on and see if it will run out a prime. Do that a half dozen times. Then do your bench run. Some don't like the idea of using a starter, but not everyone has the patience and skill to do it any other way. I have run them without this lapping procedure, by carefully priming and bumping with a stater. As soon as the cylinder fires the first time, the cylinder expands and lets things happen. It takes several tank falls of fuel to run in, but it is tricky to start this way. You can't over prime it or it will flood and off goes your spinner! Once you get some runs on it and it starts acting more friendly, you cam put it on an airplane. But it will still take a lit of running to be broken in, but you will never wear it out. I think it was Ken Cooke that told me that if the enginexstill felt stiff  the main bushing might be a bit tight. Take the engine apart if you want and polish the crankshaft bearing surface with really fine sand paper. You are not trying to remove any metal, just polish it. The Norvel I have in a stunt model gave me fits or a while, but kept at it until it got enough time on it that it started to behave. The APC 5.5 by 2.5 prop that was recommended by Ken and some others and that helped. Search out some threads in the 1/2A section on this engine and my posts on it as they have been pretty recent. You CAN NOT run this engine like a Cox engine. It is a different animal, but once you get used to it, I think you'll  like what it can do, and you can still use and run Cox engines when you wish. I do!
  Type at you later,
  Dan McEntee

Roy

A gent (now departed) named Rockin' Rusty developed a great way to break in these Norvels. He used a heat gun. I tried it and it worked, turning my Norvel into a screamer. You could use it in conjunction with Dan's great suggestions. I can forward the instructions if you send me a PM here.

One other thing. I found that attaching the glow clip's lower jaw to the cylinder fins didn't work. Attach it to a head fin instead.

Dave Mo...

FYI,

Quote from: Brett Buck on March 02, 2026, 11:20:12 AMIf you turn it over at low speed (like by hand) or worse, with the glow plug out, it is supposed to bind/squeak when cold. The top of the cylinder expands when it is running to a proper fit.  DO NOT use Marvel Mystery Oil or anything like it. If you absolutely must put oil in it, only tiny amounts and as thin as you can get it. '
 
  My suggestion is to just run it on *recommended* fuel. No Fox Superfuel, Powermaster GMA, or any high-castor content fuel.

    Brett

    I forgot to cover fuel. SIG was the main distributor and importer for Norvel in it's early days, and they sold "Norvel" fuel with the Norvel logo and such on it. It came in varying nitro contents, but mainly 15% through 30% and the oil content was 18%. Sitting next to a jug of SIG Champion 50/50 Klotz and castor oil fuel, it looked exactly the same. I have a quart bottle or two of it here. At KidVenture, Mike Gretz would bring a coup0le of jugs of Champion 15% fuel to run them with. We were just flying round and round with trainers but there were no problems with the engine. Now that I can post some pictures, when I get back from a doc appointment I'll post a pic of the bottle. It is a plain bearing engine so you need something in it for that. I regularly run mine on a Champion like 10% nitro mix and have been happy. I don't think a full synthetic fuel would be an issue as long as you kept the content up close to the 15% range.  I think they might really run OK on just about anything 20% oil or a bit less, just from my experience with them. If you can get Morgan Fuels Omega where you live, that may be an acceptable fuel, and if you want to you can add a touch of castor.  I wish the weather would get better so I could get mine out again and lick up where I left off, if I could remember where that was!!
  Type at later,
  Dan McEntee

Quote from: Dave Moritz on March 02, 2026, 12:17:54 PMRoy

A gent (now departed) named Rockin' Rusty developed a great way to break in these Norvels. He used a heat gun. I tried it and it worked, turning my Norvel into a screamer. You could use it in conjunction with Dan's great suggestions. I can forward the instructions if you send me a PM here.

One other thing. I found that attaching the glow clip's lower jaw to the cylinder fins didn't work. Attach it to a head fin instead.

Dave Mo...

FYI,

    I didn't think of the heat gun trick. Dave Gierke first suggested that years ago!!  You can probably use the heat gun and run it in the old fashioned way, just have to play with it to figure out the procedure. I forgot to mention the glow clip also. The cylinder is ceramic coated, won't conduct electricity. There are several common clips that can be used, including the old Cox clip but check the wires to make sure they aren't corroded and not passing current!! I'm off to teh doc and when I get back I'll post pics of those also.

  Dan McEntee

            In addition, if you have the instructions, Norvel provided additional head shims taped to the instructions. Adding another or two will certainly ease starting for the first few tries. I've consistently witnessed the stock plug generally burning out when the engine is near 1 hour run time. Once the engine is running, try not to run it too rich, lean it up a bit not flat out  and run it for two minutes to get some heat into it.

Thank-you for the great suggestions and guidance. I wanted to believe it was normal. It was the double bump that was throwing me off. The I thought it thru that it was sticking just before top dead center and just after. The piston probably not moving but just the rod doing it's thing going over center. I will give her a try. Thanks again!

Quote from: Brett Buck on March 02, 2026, 11:20:12 AMIf you turn it over at low speed (like by hand) or worse, with the glow plug out, it is supposed to bind/squeak when cold. The top of the cylinder expands when it is running to a proper fit.  DO NOT use Marvel Mystery Oil or anything like it. If you absolutely must put oil in it, only tiny amounts and as thin as you can get it. '
 
   My suggestion is to just run it on *recommended* fuel. No Fox Superfuel, Powermaster GMA, or any high-castor content fuel.

    Brett

I don't know what the recommended fuel is, but you can protect the piston surface during pinch with a tiny amount of good quality castor oil during the first starts. I mean just a drop or to exhaust port before priming.
Castor has a better pressure resistance than many other oils, and you will notice much less pinch with that.
Or, you can heat the cylinder head a little before first starts to make it expand. L

Quote from: Roy Lane on March 02, 2026, 02:53:30 PMThank-you for the great suggestions and guidance. I wanted to believe it was normal. It was the double bump that was throwing me off. The I thought it thru that it was sticking just before top dead center and just after. The piston probably not moving but just the rod doing it's thing going over center. I will give her a try. Thanks again!

    I was working at the local hobby shop at that time that the Norvel engines hit the market. We had a really high return rate on them because the customers just couldn't believe that YES< that was NORMAL for the engine!! We had some crusty old timers that simply would not buy into it and read the instruction. The Nelson and other high pinch high performance engines were just hitting the market also back then and wee not widely known by the average "Joe Modeler." The first engine like that I remember seeing was some combat engines that the late Gary Frost was using, and I can't remember what they were, the Willey, or his first Nelson .36s. I had a hard time believing that this was acceptable at that time also!!
  Here is the picture of the glow clip and the Norvel fuel. I haven't found the bottle of Norvel fuel that has the oil content on the label yet but I'm pretty sure it was 18% total oil. The glow clip is the smaller of the DuBro spring loaded clips that take some getting used to, but they hold on very positively and just take some practice to get off once the engine is running. I  grab the black plastic body and pull straight back then lift. I think I had to do a tiny bit of grinding on them to get a bit more clearance, but I like them so far. They aren't made any more, but lots of them out there and you might have one in your junk drawer that you don't remember. They show up on eVilBay also, and look for them at swap meets and such.
  Type at you later,
  Dan McEntee


     

  And here is the fuel bottle. I couldn't get them in the same reply.

  Type at you later,
  Dan McEntee

   

I'm going to cheat a bit re: the Dubro Glow Clip. Please drill down to the end of the topic to see a pretty good modification to the clip Mr. Dan recommends. I believe one can view the pictures in the topic while visiting (no logon required, but the nag pop-up can be bypassed).

https://www.coxengineforum.com/t15412p50-solvedmost-efficent-glowhead-clip-for-norvel-engine?highlight=Dubro

Oh, and if the engine is a RevLite version, expect the exhaust goo to be particularly dark like a pencil rubbed on paper.  This is normal and is part of the coating polishing smooth as the engine runs. My 0.074 Big Migs did this for quite some time. Eventually the coating stops shedding the high spots.

Quote from: 944_Jim on March 03, 2026, 02:02:06 PMI'm going to cheat a bit re: the Dubro Glow Clip. Please drill down to the end of the topic to see a pretty good modification to the clip Mr. Dan recommends. I believe one can view the pictures in the topic while visiting (no logon required, but the nag pop-up can be bypassed).

https://www.coxengineforum.com/t15412p50-solvedmost-efficent-glowhead-clip-for-norvel-engine?highlight=Dubro

Oh, and if the engine is a RevLite version, expect the exhaust goo to be particularly dark like a pencil rubbed on paper.  This is normal and is part of the coating polishing smooth as the engine runs. My 0.074 Big Migs did this for quite some time. Eventually the coating stops shedding the high spots.

    Good to know, because that was exactly what mine was doing!  Do you have enough running to figure out if the RevLite (AAO) cylinder/piston is durable enough for stunt?

    Brett

Quote from: Brett Buck on March 11, 2026, 09:36:12 PMGood to know, because that was exactly what mine was doing!  Do you have enough running to figure out if the RevLite (AAO) cylinder/piston is durable enough for stunt?

    Brett

   I wasn't aware that the different Norvel engines had different material make ups in their construction?? Are they not all aluminum piston with ceramic coated aluminum cylinders?? I have a Big Mig .061 in the Doodlebug that I have been flying , and got quite a few flites on it now and it still gives up some black goo, but I attributed that to metal being made by vibration between the cylinder exhaust stack and the muffler. The music wire bale that they use to retain the muffler isn't quite adequate, but it improves with even a simple twisted loop of safety wire. I also put some high temp silicone along the edge to try and glue it in place as much as possible. We used the Big Mig on the trainers we built for the KidVenture circles at Oshkosh and some of those had untold numbers of hours on them. Some got tired enough to need a starter to get them running but they started right away and still ran well. These were just going round and round but the run wouldn't be any different for a stunt model, I would imagine.
  Type at you later,
   Dan McEntee

I'm afraid I can't add anything WRT stunt. I can handle flying inverted and figure nines...assuming I started upright on a good take off.

Mr. Dan,
My Big Mig .074s had mufflers screwed to the engines, not wire bales like the smaller ones. They are the ones I have the longest time on. They really blew grey exhaust/oil when I first ran them. As the hours piled up, the exhaust cleaned up quite a bit.
The coating reminds me of how I had my 1983 CB1100F engine treated decades ago. I had to buff the friction side of all bearings, piston skirts, wrist pins, tranny gears and valve components using worn out green scrubbing pads and new engine oil. The exhaust goo on the airplane's engines/wings reminded me of the pads and motorcycle parts dripping oil with suspended coating particles in it.

            Dan, as your probably aware that there were several versions of the Norvel. I'm quite certain there was some connection between the AME brand ( Not to be confused with the porting)  which made the Zeus and what has come to be known as Norvel. Northern Velocity was somewhat in between the two. The Northern Velocity versions were called MKII which came in blister packs on a 3x5 card and still used the glued in venturi. It wasn't until these were branded Norvel that the engines had bolt on venturi and the case itself was slightly longer in the nose. This was when the round Rev-Lite ceramic coated versions were offered. Up until the arrival of Rev Lite versions were the squared off cylinders offered. I'm not a expert in metallurgy but the plating on the older versions is not shiny like chrome. It certainly appears to be nickel plated. I did have a side exhaust Stels which appearance wise looked the same but it has a unplated cylinder.  The internal  cylinder plating on the Stels was certainly chrome. This particular version ran unbelievable. I wore out the case and it developed substantial side to side play. These engines had a expected lifetime of approx 8 hours according to the directions.  Now if that's not confusing enough, I also have a Rev-Lite versions which is not the round cylinder but the squared of style like what I'm referring to as ABN.

            One particular area of concern though with these engines is that Norvel designated the engines as Big Mig and AME for the porting differences. AME was now not only a brand but a now a porting style.  AME used a larger venturi (Not all the time) and it had a different cylinder porting. This can make identifying the engines difficult because they look the same. TO add more confusion, Norvel couldn't easily identify them and many were put incorrectly in the boxes. Norvel even at one time was using different style needle valves as a identifier. I think that added even more confusion. The AME version needed assistance in fuel delivery and without knowledge of running one, I'm quite certain it was a huge negative for users. This engine required pressure to run correctly be it muffler, bladder or crank pressure. Many did indeed come with a backplate with pressure nipple. The problem with the nipple was that the hole was too large. The simple way to identify cylinder porting is to remove the head and look into the cylinder. 3 large cutouts in the cylinder is AME porting, 5 smaller cutouts is a Big Mig.

              I've had extensive experience with both and I like them both but understanding the quirks is important. The AME in my opinion requires a bit more nitro and a smaller diameter propeller whereas the Big Mig can swing a slightly larger propeller. The biggest problem I've been faced with is the wrist pin. The wrist pins are staked and non removable. That is until you get some time on the engine and the wrist pin hole on the piston lines up with the porting cutout on the AME versions. The wrist pin staking wears down which can and will slide out into the cutout destroying the cylinder. I've landed after running out of fuel and had the pin slide out  enough so that the engine couldn't rotate. I was able to dismantle and re stake the piston in a V-block. I've experienced this on  three AME engines to date due to the wrist pin getting jammed into the port. The Big Mig doesn't have this issue as none of the cutouts line up with the wrist pin. 

I would pre-heat the cylinder and head with a heat gun or perhaps even a propane torch (applied carefully and with an extinguisher handy) to expand the cylinder before the first bench running. The question I would have is should it still be the old rule of multiple 2 minute runs allowing to cool down after each, or to run it longer and maybe even refuel and restart without cooling completely. I've never had an ABC or AAC engine that had significant pinch before running, and those that might have (PA and RO-Jett) werre aquired 2nd hand and pre-run at least. 

Quote from: Steve Helmick on Yesterday at 09:42:25 AMI would pre-heat the cylinder and head with a heat gun or perhaps even a propane torch (applied carefully and with an extinguisher handy) to expand the cylinder before the first bench running. The question I would have is should it still be the old rule of multiple 2 minute runs allowing to cool down after each, or to run it longer and maybe even refuel and restart without cooling completely. I've never had an ABC or AAC engine that had significant pinch before running, and those that might have (PA and RO-Jett) werre aquired 2nd hand and pre-run at least. 

??  Even my #2 RO-Jett, after running it almost exclusively for almost 20 years, still has a "pinch" and will stick hard at TDC if you try to turn it over with the glow plug out. Almost every Magnum I have seen was put in the box with the piston at TDC and so stuck you can only get it loose with a heat source. Even VFs will have a noticeable interference at TDC straight out of the box.

   Brett