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Combustion Video

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aeronca65t

aeronca65t

Great Pumpkin
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Roger, the valves are <u>supposed</u> to rotate. If they didn't, they would always seat in the same spot, and their life would be extremely short.
Jeff
 
Very cool, not what I expected. I envisioned a big fireball. That looked more like the Aurora Borealis, 'cept it was a different color. Well, you know what I'm gettin at.
 
Did ya notice how much of the flame was focused around the edge of the intake valve. That is a great video and I wonder how they were able to take it.
 
vping said:
That is a great video and I wonder how they were able to take it.
Click to expand...
A fiber optics video camera. A bunch of years ago I worked on a project for one of the major auto manufactures where modified sparkplugs to put a pressure gauge in. The hooked them up to an oscilloscope to see how the pressure varied during combustion.
 
Hello all,

very interesting indeed, I am surprised how much raw flame there was, i.e. the yellow parts, poor combustion or oil burning?

Jeff, just what causes the valves to rotate?

Alec
 
By design it could be several things. Most common is there is a slight bevel in either the valve stem or the rocker that contacts the valve stem. So that instead of the valve stem rocker contacting full face, it is actually touched just very slightly off center, so that when pressure is applied it turns it slightly. Also there may be a valve rotator in the valve spring stack that turns slightly, but those are going out of style pretty much anymore.
 
That IS cool!

But it seems like part has been edited or clipped. Each time the exhaust valve begins to close, all of a sudden the film jumps past that part of the cycle. Anyone else notice that?
 
Hello Ron,

forgive me for being sceptical, but I have never seen either a beveled valve stem tip or rocker tip. And how about an overhead cam engine?
Certainly some engines had rotational valve caps but not so many.

Alec
 
Even if there is a bevel/curvature, it's too small to be seen with the naked eye. Even the radius on lifters is virtually impossible to see without a straight edge, and they are many times wider than a valve stem.
 
Alec,

Do you have an engine machinist shop nearby? A really old timer one?

If so, please visit him and chat with him. Ask about his valve refacing machine(over here the main brand was Sioux). Get him to open up about facing the edges of the valve stems.

If you look at rockers on overhead cam engines(I'll use Honda and Acura and Mercedes for example as I have over 30 years line experience with those mfrs.) you will notice that there is a bevelled pad on the end of the rocker where it contacts the valve stem.

Might wanna do a google search for valve spring seats and see what you can find out about the ones that do a little bit of turning each time the spring is compressed.

Most common problem with a valve burning is that it quit turning on the seat and the heat is not transferred properly.
 
Bugeye58, you must be right. Now I recall, when rebuilding a Chevy 6 some years ago, that there were serrated washers under the valve springs. I was told these were to make the valves rotate. I don't recall a similar arrangement on any MG or Jaguar engines I have rebuilt.

It makes sense to have the valves rotate, so that a hot spot between the valve and seat can't develop.

I have heard for many years that there is supposed to be a "flame front" that travels out from the point of ignition, however, in this video, the only significant flames I saw seemed to be coming off the intake valve.

Fascinating video.
 
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