head shims

[Dan Berry]

Greetings all.
I need some help/guidance/advice/info.
I have a Tower 40 converted froma r/c version. I have little doubt that it is over-compressed for CL stunt purposes.
I am not up to the task of making head shims. I cannot find a source for them. I think the Tower is a clone of a particular OS 40 but I do not know which. Is there a chance of getting shims for an OS or another 40 that I can make work?

Thanks in advance.

[Bill Hummel]

Dan, any of the 40 FP, 40 GP engines are clones.  Randy Smith likely can help with head shims, worth giving him a call (Aero Products).
Worst scenario, drop me your address, I have a few to spare.

[Dan Berry]

Randy was the first choice when I got the engine and started the plane.
He's Out Of Stock.
GP is Great Planes?

[RknRusty]

I've made them from beer can aluminum with an exacto blade clamped to a caliper like this one: 
A few passes around the circle cuts it cleanly.
Rusty

Waiting to be laughed at.

[Dan Berry]

Welllll, I do have a supply of Pabst Blue Ribbon cans available.
A project for tomorrow.

[Dennis Moritz]

Leonard Newman (Stuka Stunt) had them cheap in the past. Fp40 gasket kits from Tower have one in pack. Fp gaskets .015, Tower and Leonard .010. (or is it .0010 and .0015?)

[Geoff Goodworth]

Dan, GP40 refers to the Thunder Tiger/Magnum GP 40. Two brands, one model number which came out of the same factory in Taiwan.

They were an FP 40 clone except that they can use a true venturi with the NVA to one side rather than through the venturi like the Tower and the FP

I bought several new around the turn of the century but I believe that they are no longer available.

Thunder Tiger is still made in Taiwan while Magnum is made in China. I don't have any of the recent examples so cannot comment on interchangeability.

[EddyR]

As Rusty said they are quite easy to make. You can use very soft aluminum that Home Depot sells for roof repairs, some times called  flashing. 
Ed

[Dan Berry]

Clamp the head in a vise and file it down.


MM

I'm gonna have a go at making some shims.
Might need to change my name.

[john e. holliday]

Lee Machine Shop has a tool for making gaskets.

[Jim Thomerson]

My stock Tower 40s ran to suit me with a venturi and ST NVA, like a sewing machine, one of my buddies remarked. 

I did have an odd situation with a couple of them.  Compression was so high I could not start them.  Took the glowplug out and the high compression went away.  I had a spare head and took the dremel to it to cut some grooves and lower the compression.  I could start and run the engine with this head.  After one run, the engine would start and run fine with a regular head.  I never did figure that out. 

[Brett Buck]

My stock Tower 40s ran to suit me with a venturi and ST NVA, like a sewing machine, one of my buddies remarked. 

I did have an odd situation with a couple of them.  Compression was so high I could not start them.  Took the glowplug out and the high compression went away.  I had a spare head and took the dremel to it to cut some grooves and lower the compression.  I could start and run the engine with this head.  After one run, the engine would start and run fine with a regular head.  I never did figure that out. 

    I have had engines that were exceptionally difficult to start the first time and were (as it say in several British engine instructions) "fierce" from high compression.  I was usually able to get them started once, and then, after that, no problem. Same thing, seemed fine with the plug out. I never figured it out either. I speculated that the piston was jamming in the bore briefly near TDC as it fired, and that went away after the bore got smoothed out, but that was just a guess.

    Brett

[Dan Berry]

Pabst can to the rescue.
I made one. It is 004 thick. I'll probably generate the nerve to make another. It took four tries.

[Geoff Goodworth]

Following on from Dan's latest comment, a few thoughts.

First we are talking about a 40. Does anybody know whether the LA 40 head gasket will fit the FP and clones? I don't have an LA 40 so I can't check.

Next is gasket thickness. The factory OS gaskets for the FP 40 were 0.016" thick. The tech data for the Tower 40 used to say that they were 0.010" thick as are, I believe, the GP 40 items—if you have any. According to Tower, the gasket for the LA 46 is 0.013" thick.

[RknRusty]

Pabst can to the rescue.
I made one. It is 004 thick. I'll probably generate the nerve to make another. It took four tries.

Wow, that's some thin stuff, if you make a few, at least you can really fine tune it. Did you use the caliper and blade method? I use the Titanium nitride(or zirconium or something like that) coated exacto blades. Gold colored edges. They might hold up better.
Rusty

[Dan Berry]

No knife, just a divider with a sharp point.
Pabst cans don't hafta be real thick.
Mostly I fly Free Flight. It is well established that Pabst Blue Ribbon can stock makes the best thrust adjustment shims so I figured they would work for heads. I might get to find out tomorrow. I've gotta do some shorter lines also. I don't really know what I;m doing.

[Steve Helmick]

Following on from Dan's latest comment, a few thoughts.

First we are talking about a 40. Does anybody know whether the LA 40 head gasket will fit the FP and clones? I don't have an LA 40 so I can't check.

Next is gasket thickness. The factory OS gaskets for the FP 40 were 0.016" thick. The tech data for the Tower 40 used to say that they were 0.010" thick as are, I believe, the GP 40 items—if you have any. According to Tower, the gasket for the LA 46 is 0.013" thick.

Letsee...The LA .40 crank is a direct replacement for .35FP, .40FP, and .46LA. Also the TT GP .40 and Tower .40. Since we therefore know that the stroke is the same, all the .40's would have the same bore, so the head gaskets & shims would all interchange.  But very often, bore/stroke ratios are similar and that means the head gaskets/shims of any brand will often be real close. Yes, there are exceptions.  Steve 

[Dennis Moritz]

See if Leonard still has these gaskets. Definitely cheapest price I found. What plane are you planning to fly with this engine? What muffler do you plan to use? What prop? What fuel? I use these engines extensively. I doubt you will need more than one FP (.015) or 2 Tower 40 (.010) gaskets to tune in. Venuri range is from .256 to .283. I run a 101/2x41/2 APC prop and most stunt planes that are appropriate for this engine. The pinch can be tight with a new engine. I have run these engines with the stock single gasket on sport planes. They howl. Compression can be high enough to stall my electric starter. For stunt planes I put in the extra gasket or gaskets. Venturi size has a big effect on tune. I always use a free flowing tongue muffler.

The Tower on this 36 ounce Magician had one extra Tower gasket, 273 venturi, free flow tongue, 101/2x41/2 apc. Very well matched combination.

[kenneth cook]

            Another option would be to find a FP .40 head as they're not the same combustion chamber as the Tower .40. They're is a slight difference and both are interchangeable. One may just work better than the other. Ken

[Dan Berry]

The plane is a Oriental profile.
prop is 10.5 x 4.5 APC, 5% pop in the fuel. I've been on 65' lines.
The engine as I got had no head shims in it and was reall tight.
If I set it to make anything resembling a 4-2 break on the ground it won't do a wingover in the air-not enough speed.
By the time I get it fast enough to stay overhead, it's just a flat 2 cycle and frankly must be too fast for me to learn anything resembing a square maneuver. It also will run about 8-9 minutes on 4.5 oz fuel.

My email for Leonard isn't good. He was gonna get some shims but I've not heard from him.

[Dennis Moritz]

Leonard was just at the NATs. Try again. Maybe he'll respond. I think RSM has shims. Otherwise you can buy a gasket set for an FP40 from Tower. It has one .015 FP head shim. That should calm your engine down some. Looks like you are running a tongue muffler. Might need more holes or bigger holes. Are you running a tongue muffler or no muffler? Check the venturi size. Sounds like your engine is putting out too much power. A smaller venturi might put it in a more optimum power range for your plane. I like .272 venturis, midway between the big .283 and the small .256. Not a 4/2 break engine. A 2/2 break. A richer 2 into a leaner 2. The rich 2 can sound mean with barely any miss. The setting you want on the ground. For me, when these engines are working correctly, there's only a bit of a miss on the ground. Flying the shapes will cause the engine to lean a bit and provide more power where useful.

[Dan Berry]

I'll try Leonard again. RSM shows OOS.
I have opened the venturi a few times. It doesn't use much fuel.
Guys here recommended a 4.5oz tank and it's way more than I need so far.
I must believe that less compression will calm it down a bit.
2/2 break sounds reasonable.
Intermediate pattern, here I come.

[Steve Helmick]

The plane is a Oriental profile.
prop is 10.5 x 4.5 APC, 5% pop in the fuel. I've been on 65' lines.
The engine as I got had no head shims in it and was reall tight.
If I set it to make anything resembling a 4-2 break on the ground it won't do a wingover in the air-not enough speed.
By the time I get it fast enough to stay overhead, it's just a flat 2 cycle and frankly must be too fast for me to learn anything resembing a square maneuver. It also will run about 8-9 minutes on 4.5 oz fuel.

My email for Leonard isn't good. He was gonna get some shims but I've not heard from him.

Are the lines 65' eye to eye or center/center? In either case, I would suggest that the lines are too long. I fell into that trap... thought the longer the lines, the bigger the tricks, the easier it would be. That didn't happen. I can't predict an exact line length that will work, but would suggest 60' to maybe 62' eye to eye. Funny thing, but good reliable line tension is what really makes things easier.  Steve

[Dave_Trible]

Greetings all.
I need some help/guidance/advice/info.
I have a Tower 40 converted froma r/c version. I have little doubt that it is over-compressed for CL stunt purposes.
I am not up to the task of making head shims. I cannot find a source for them. I think the Tower is a clone of a particular OS 40 but I do not know which. Is there a chance of getting shims for an OS or another 40 that I can make work?

Thanks in advance.

I think I would try it FIRST before I worry about the shims...bet you don't need them.  I've converted a couple R/C engines and never found the need to add shims.

Dave

[Dan Berry]

Are the lines 65' eye to eye or center/center? In either case, I would suggest that the lines are too long. I fell into that trap... thought the longer the lines, the bigger the tricks, the easier it would be. That didn't happen. I can't predict an exact line length that will work, but would suggest 60' to maybe 62' eye to eye. Funny thing, but good reliable line tension is what really makes things easier.  Steve

65" eyelet to eyelet. I've started to think they are too long after reading Allen Brickhaus' article in FM about his green/yellow Oriental. His lines are under 60 feet.
The palne weighs 39oz. That includes 1 1/2 oz tail weight. Hindsight says I shoulda move the engine back a bit since it was drawn with a Fox 35. I don't fly great but I'm a big fan of line tension.

[Dennis Moritz]

Yep. 65 eyelet to eyelet seems long. On planes that size with that power I typically use 60' eyelet to eyelet. The use of shims, venturi size variation, prop switch, all part of tuning the engine to provide optimum power in a specific plane.

[Jim Kraft]

I too am a fan of shorter lines. I fly my Magicians with McCoy 40 Red Heads on 58' eye to eye lines. It is slightly on the fast side, (I have never checked lap time), but I have great line tension everywhere. I also run just a little over on tip weight for flying in Kansas wind. I can sometimes see the outboard tip drop just a bit in a hard pull out. But with a 12-6 APC prop cut to 11" it flys a very constant easy to fly speed. All of my Magicians have weighed between 35 and 38 ounces and have great line tension everywhere. I think Brett Buck said one time to run the shortest lines you feel comfortable with, and I think that is a good place to be. It may not work on other plane engine combos, but the McCoy is such a lugger that it works real well for me.

[Jim Thomerson]

I did some prop testing, but did not try the usually recommended 10.5 x 4.5. I settled on the Supercool carbon 11 x 5 petal blade and it worked fine.  I had 65 ft eyelet to eyelet lines.