T head engine by Brian

[sid pileski]

How is the compression???
Are you going to do your run in thing now?

Sid

[brian Rupnow]

Right now the compression is marvelous, but there is oil all over everything, so it isn't a fair test. I did my "run in" thing yesterday while the engine was all assembled (except for the rings) and it loosened up quite a bit. All I have to do now (I hope) is set the valve lash, set the valve timing, and set the ignition timing and make up some gaskets. I have no idea of when my flywheels are coming, but I see their charge on my credit card.

[Tim Clarke]

Yup. I had one made from an old cylinder liner when I rebuilt Detroit Diesels. Passed it on to a kid in the shop when I retired, said: Here ya go, kid, I hope you never need it!

[brian Rupnow]

Tim---I have no idea what you are talking about. Did you post in the wrong thread by mistake? Today has been a day of cleaning, sanding, and chasing down tight spots. I am always somewhat amazed at how much dirt these little engines make in the final moments of assembly prior to running. A ton of grey sludge seems to come off all of the aluminum parts and even from the cast iron parts. Today I installed the gasket that fits between the two halves of the crankcase and the gasket that fits between the top of the crankcase and the underside of the cylinder assembly. Tomorrow I will make the head gasket and probably make a gasket to put between the cylinder top plate and the cylinder body itself. I haven't heard a peep from the folks at Martin Model about shipping my flywheels, but I see that they have put the charge on my Visa. in a perfect world, I would receive the flywheels before I finish everything on the engine, but it's getting tight. I will set the ignition and valve timing tomorrow, and then there really isn't anything left for me to do. (I say that with tongue in cheek, because I never know until the very last minute if my valves are going to seal or not).

[Joel]

He used the liner as a ring installing sleeve, similar to what you did.

[brian Rupnow]

Thanks Joel--Now it makes sense.---Brian

[Tim Clarke]

Sorry, Brian. I was in a bit of a hurry, and another sentence or two would have made it obvious what I was talking about!

[brian Rupnow]

All right!!! Engine is timed, both valves and ignition. I didn't use a degree wheel. I set my crankshaft at whatever angle I want in my 3D program, then measure down from the top of the cylinder to the top of the piston. Then I set my vernier for that distance, turn the engine by hand in the correct direction until the piston touches the depth gauge end of the vernier. Then I loosen off the screws in the crankshaft gear on the side I am timing and rotate it until the valve just begins to open (this is quite visible because the cylinder head is removed). Ignition timing is set to about 5 degrees before top dead center. I always go a little crazy doing the timing, because I have to remember which side I am putting the starter fixture on, and then remember which side of the engine I'm working with and knowing that on the far side of the engine the crankshaft will be rotating in the opposite direction.

[aostling]

In the (unlikely) event that the timing gears will supply enough inertia, give it a go while waiting for the flywheels. We can't wait!

[brian Rupnow]

Aostling--I have to do some real work tomorrow on design changes to a welding fixture for one of the big three automakers. I keep presenting designs and they keep having review meetings and changing them. I'm glad to be almost finished with this engine, so I can wait a few days until my flywheels get here.---Brian

[brian Rupnow]

Today I milled keyways into both ends of the crankshaft, finished making gaskets, and mounted the cylinder head and sparkplug. At this point, turning the engine over be hand, I can't really tell if I can feel compression or not. That is not unusual, because my new engines are a bit stiff. Tomorrow we are having a family birthday party for my second oldest granddaughter who is turning 14 and my mother who is turning 101. There isn't much more that I can do to the engine now until my flywheels come.---Brian

[brian Rupnow]

Party doesn't start till later in the day. I decided to perform the old, tried and true, "Blow yer Guts Out" test on the engine. This is a simple diagnostic test. You have to sacrifice a spark plug, by chipping out all of the porcelain and soldering a small tube to the sparkplug to which a piece of flexible gas line is attached. This lets you put the other end of the tube in your mouth and "Blow yer Guts Out". In a perfect world, when the engine is at top dead center on the compression stroke and both valves are fully closed (as verified by seeing daylight between the valve stem and the valve lifter), then you shouldn't be able to blow at all. If you can blow, and the air comes out of the exhaust system, then your exhaust valve is leaking. If you cover the end of the exhaust with a finger and you can still blow, then probably your intake valve is leaking. If you cover the intake and the exhaust with your fingers and can still blow, then your rings are leaking. (you have to remove the oil filler plug for the ring test). From what I see today, the exhaust valve and the intake valve are leaking a little bit. The rings don't seem to be leaking at all. This doesn't surprise me at all, and it is a simple operation to pop off the cylinder head and the top part of the cylinder assembly which has the valve cages in it. A little more dressing with 600 grit aluminum oxide paste will probably fix any current valve leaks.

[DrMike]

Brian... Do you happen to have a compressor?
Seems like this (very valuable) test might be easier done with ~120 psi generated by some machinery than a set of human lungs.

Maybe the next project might be some "standard" engine test equipment?
A series of "Rupnow tests" for model engines?
Just a suggestion....

[brian Rupnow]

Yes Mike--I do have a compressor. If a valve leaks at the 5 psi that I can blow, then it will only leak more at 100 psi.

[brian Rupnow]

After a bit of redressing the valves with 600 grit, everything seems to be sealing okay. Today is going to be an "at the beach" day with one of my grandsons, but I had time this morning to redress the valves. Now it's simply a matter of waiting for flywheels. They were shipped to me on the 8th of August. 16 days and counting---