T head engine by Brian

[Brian Rupnow]

Compression has improved. Engine is now firing regularly along with power drill as I attempt to get it to take off and run on it's own. Cylinder is getting hot from firing. I am now going to take my degree wheel and check the ignition timing. The common knowledge out there is that four cycle engines should fire about 20 degrees before top dead center. Lots of puffs and snorts from the engine but haven't found the sweet spot yet.

[crueby]

Sounds like great progress, looking forward to seeing it go!

[Admiral_dk]

It sounds like you are getting very close to a runner 

It might be one or a few minor details that are the last difference between a great runner and one is trying - as you know - so I hope that you find those soon 

Per

[Art K]

Getting real close now!
Art

[Brian Rupnow]

No joy today. Very, very close, but no engine running on it's own. I'm having some kind of compression issue, and I think it is in the valves. Tomorrow I will reset the valve timing with my degree wheel, but my gut is saying it's a valve sealing issue.

[Jasonb]

My engines tend to run a 5 to 10deg BTDC, your 20deg sounds a bit early to me particularly for these slow running types.

That way you are more likely to get all the explosive force pushing the piston down, too early and that force is pushing down on the piston while it's still coming up and on it's own the engine does not have the power to overcome that. Also tends to cause more backfires but you won't be seeing that pushing it round with an electric drill, I see it more as mine get started by flicking the flywheel or a short pull cord.

EDIT I just looked at what hamilton Upshur suggests for his Tee Head and it says "a little Before TDC" which I would take as less than 20deg, also suggests 0.010" points gap.

[Brian Rupnow]

This morning I am waiting around for my electrical friend to come over and wire up my VFD to run my new bandsaw. I thought "Right now, while my t-head engine is cold, I'm going to try something." I turned it over by hand, and there is very little or no compression. After fooling with it all day yesterday, the engine has loosened up considerably, and I can feel the compression (or lack of) when turning the engine by hand. Pulled out the sparkplug, squirted some oil into the cylinder and then replaced the sparkplug. Surprise!!! Engine now has scads of compression!!--I have a lifetime supply of viton o-rings, and it only takes me a couple of hours to make a piston. Before I go screwing around with the valves any more, I am going to quickly make a new piston fitted with a viton o-ring. If that fixes things, I will revisit my cast iron rings.

[Bearcar1]

save your breathe Jason.

[Brian Rupnow]

Bearcar---that is a very strange post. I read all of the responses to any thread I start. I don't always immediately run and do what people suggest. Sometimes I do, sometimes I don't necessarily agree with the poster and I don't.  I'm not looking to start a flame war with anyone. Sometimes I will post my immediate thoughts on what I plan on doing next, sometimes when I've thought about it for a while I decide to approach the problem a different way. Before I make a new piston I am going to check my valve timing with a degree wheel. The valve timing was initially set using measurements from the top of the cylinder down to the top of the piston, taken from my 3D model when the crankshaft was positioned at the correct number of degrees before top or bottom dead center. I will certainly check the valve timing again with a degree wheel just to be absolutely sure of it.

[Brian Rupnow]

Okay Kiddies---It's showtime. Yesterday I had worked my way right into a snit trying to get this engine to run. I was almost at the point of making a new piston with a viton ring to get more compression. I decided that before changing anything, I would bring the engine in from my big garage and use a degree wheel to set the valve timing exactly "on spec" and to reset the ignition timing to about 12 degrees before top dead center.--I discovered that the grub screws in the gear which drives the exhaust valve had backed off and the exhaust valve timing was way out of whack.  So, in the end, I really didn't change anything. The engine runs very well, and after playing with it a bit as "final tuning" I will reinstall the gear covers and clean everything up.   If you would like to build this engine, I sell a complete plan set of engineering drawings, including detail drawings and assembly drawings for $25 Canadian funds, paid to Paypal to brupnow@rogers.com    Thank you to everybody who followed the build, and thank you for your posts and the information you have given me.---Brian Rupnow
<a href="https://www.youtube.com/watch?v=O_kE2aVUvWc" target="_blank">http://www.youtube.com/watch?v=O_kE2aVUvWc</a>

[crueby]

Super!!   

[Don1966]

Awesome…..


Don

[Admiral_dk]

Great to see and hear it run - congratulations Brian.

So what is next ?

[Brian Rupnow]

If I'm bored next week, I may make a cooling fan for it. This won't be anything new, it will be very similar to the cooling fan I made for my vertical engine. These fans put out a lot more wind than you would think. When the engine is running at 1000 rpm, the fan is turning at about 5600 rpm.

[Trevorc]

Well done Brian, I am envious of your skill and productivity.
Trevorc