Upshur's opposed twin engine

[pileskis]

And as the sun goes down---both cylinder heads have been pressure tested. The first cylinder head had no leaks around the valves at all. The second cylinder had very little leakage around the valves. Very small leaks will seal themselves after the engine has been ran for a while..

What is LOCTITE 638 used for?


LOCTITE® 638 High Strength Retaining Compound

Designed for bonding cylindrical fitting parts, particularly with narrow bond gaps up to 0.25mm (0.01"). Great for a fast cure on all metals, including passive substrates like stainless steel.

 

[Brian Rupnow]

And your point is?? I've done this before. It works.

 

[pileskis]

And your point is?? I've done this before. It works.

Maybe you wouldn’t have to if you didn’t take shortcuts?
What’s going to happen every time you have to take a plug out as part of the debugging process??

 

[Brian Rupnow]

No problems removing the plugs, as long as the plug has a good hex on it and you own a set of sockets.

 

[minh-thanh]

Maybe you wouldn’t have to if you didn’t take shortcuts?
What’s going to happen every time you have to take a plug out as part of the debugging process??

No problems removing the plugs, as long as the plug has a good hex on it and you own a set of sockets.

Maybe because they are not completely clean, a little oil... so the loctile glue does not work much.
Personally I would not use that glue for that position, O-rings or make a copper ring (machined from sheet or cut a copper ), it only takes a little time instead of having to fix the spark plug thread or rebuild the whole cylinder head

 

[TonyM]

Today I pulled off both cylinder heads and blew an amazing amount of crap out of the holes which lead to the ends of the sparkplugs. I checked my spark timing with both heads off, and of course I was way off where it should be, so I reset the timing to give sparks at top dead center of the piston strokes. I didn't really like that spring device I had bolted in place to hold the throttle lever from moving, so I took Jason's advice and made up a very thin brass washer to fit between the carburetor body and the rubber o ring which holds everything in place. From what I see right now, my carburetor doesn't seem to be sucking up gas from the tank when the engine is being turned over by my starting table. I'm running Viton o-rings on my pistons and both cylinders have good compression. I'll have a closer look at my cam timing tomorrow.

Hi Brian
When it is all cleaned and reassembled, check that the inlets are not drawing air around the small Jubilee clips. Those very small ones do not close round and can distort plastic tube. That's why spring clips, even home made ones are better for sealing small bore plastic tube. Assuming the tube is a reasonable fit on the spigots, then jubilee clips look a bit overkill. You shouldn't need clamps as those tubes are fairly captive and won't easily come off.

 

[Jasonb]

I doubt Brian's Loctite is working as it should hence his ability to easily remove the plugs where most of us would need to use heat to weaken the Loctite and then be faced with cleaning out it's remains.

Dirty oily surfaces are one. Excessive gap due to things like using the wrong tapping drill as previously mentioned and probably already damaged thread due to trying to seal it without a soft washer washer. Thread repair to one of the already stripped threads. Excessive Loctite applied and sitting ouside the joint which also attracts dirt.

I'd actually be wanting to test at a lot lower than 60psi as that is only likely to be reached as the piston gets towards the top of it's stroke. Far better to test the 15 to 30 psi range where the piston goes from BDC to about half way up, with less pressure on the valve that is where you can loose a lot of your gasses. Small leaks may well seal when the engine has run but they can also stop it starting in the first place, why not sort them now while the head is off instead of having to strip it down later.

 

[Hockeypuck1958]

This is awesome information, I’m glad I joined this group. Crazy amount of knowledge in this place. I wish I could sit down with some of you. Anyone live near Chicago?