engine question
 

Hey everyone. Got a question. I just bought a thunder tiger .61 pro. It's pretty much a new engine, except for one thing. One cooling fin on the head is broken off. So, I'm getting a new head. My question is, do I need a new head gasket, or can I use the old one? Thanks for any help.

RE: engine question
 

If its just one fin you dont have to replace the head but if you're into asthetics then no, you dont need to replace the gasket. Its really not a gasket so much as a shim.

RE: engine question
 

I would just fly it as is.

RE: engine question
 

Well, its a brand new plane, and the engine looks new except for that. I want it to look good for at least a little before I wreck it. Lol.

RE: engine question
 

I'd break off the fin on the opposite side to make it look symmetrical and fly it.

RE: engine question
 

Heh, yeah and or grind down the broken fin to make it look like it was designed that way. :D

RE: engine question
 

waste of money.

RE: engine question
 

What is a waste of money?

RE: engine question
 

Buying the new head I would guess. I had a student at one time that was like that, everything had to look new. He still likes things like that but now his planes look like everyone elses with patches and repairs. A broken or bent fin?? I wouldn't worry about it but to each his own!!

RE: engine question
 

Ah Ok, now I understand his response thanks.

Yup a new head might indeed be a waste of money.

RE: engine question
 

Well, its only $20 for the new head, and I don't see it as a waste of my money. Oh, are there any torque specs I have to worry about, or should I just tighten them down and call it done? Thanks.

RE: engine question
 

Torque 'em 'till they smoke, then back off a quarter turn....:D

If there's a torque value, I've never seen one. I just snug mind down evenly, then tighten the to what feels like they are tight enough they won't come undone yet not too tight that I come any where close to stripping the threads in the aluminum block. Just make sure they all feel they are tightened the same amount.

Hogflyer

RE: engine question
 

Pretty much the same as the Hog. When I open up a gas engine I do use a inch pound torque wrench set at 20 as I recall. It's more about making them even pressure. On glow engines I just set them to feel. I do use never seize on them. When it's time to rebuild I hate it when I can't get them out again. On the OS LA series engines I use a little Locktite on the four head screws. For some reason they tend to come loose?

RE: engine question
 

Use a star or crossing pattern when you tighten the head bolts doing it just snug the first time around. Then do the final tightening of the bolts the same way.

RE: engine question
 

Ok. Thanks for all the help guys.

RE: engine question
 

As others have noted it dosen't matter. As far as how it "looks" tell me if you can see the broken fin when the plane is flying?

rrragman

RE: engine question
 

Some years ago we had a club member demonstrate how he torques down the head bolts on a Fox 35 CL stunt engine. Phillips-type bolts replaced with allen-head bolts. He removes the glow plug and mounts the engine in a test stand with a prop attached. Then takes a propane torch, a can of WD40 and sprays the internal parts of the engine liberally with the WD40 then heats the upper cylinder evenly with the torch and spins the prop by hand. With the cylinder heated to produce nearly the clearance of an engine at running temperature he tightens/slackens all the allen bolts to where the engine spins over freely. This is the only way he can guarantee there is no cylinder distortion introduces and therefore cause a bind in the piston/sleeve fit which must be ground away by hours of break-in running.

It seems to work quite well. Of course, the Fox is old sintered iron piston and steel sleeve (quite thin) which must go through many heat cycles before the fit is stabilized and can be called properly broken in.

Still, nothing quite like the nostalgic song of a Fox stunt breaking perfectly between a 2 cycle and 4 cycle during different points of each maneuver.

they don't do that in the factory, I can guarantee you.