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