Over the weekend my 1926 engine was removed so that I could inspect it. Bearings, clearances, the like. I was a little concerned about how the valves looked. Number 2 cylinder, exhaust valve was kinda white, while the others were all black. To me that means this valve was hotter than the others. So that could mean that this cylinder was running a little leaner than the others. Or maybe the valve lash was too small and it did not seat completely to cool off.
The engine was running very good, plenty of power and ran like the typical Model T. Here are some pictures of the top of the engine
You can see the 2nd exhaust valve is white
The cylinder head doesn't show any difference in color between any of the cylinders that I can see.
And the plugs seem rather normal.
Maybe it's nothing, but any opinions? I figure I'll measure the valve lash later today. Thanks Mike
I'm going to stick my neck out and say something's up with that one particular valve. The plugs the head and the deck show nothing different one cyl to another.
I would check the valve lash first and if within limits check the face of the valve and the block to see if everything seals ok.
Are these adjustable or standard?
FWIW, that's cylinder #3 not #2.
I would say that 1,2 and 4 are burning oil and the gray/white deposit look about what it should. Not knowing the history of the plugs and how long they have been in the engine does not give real info on them.
I would agree with Mark. If #4 is too little lash, it would be burnt in the area where the valve seats. Oil burning will cause a lot of oily carbon. From the picture (which is kind of hard to see) of the pistons, those cylinders also seem to have more carbon on top of the pistons. And 1 &4 spark plugs also have more carbon.
This evening I had a chance to look a little closer. I have standard valve lifters. The valve lash is about 0.015". All the valves have about the same clearance. Sorry, you are correct it is cylinder #3. It could be that the other cylinders are burning some oil. I want to remove the pistons and check clearance and the rings. I removed the valves on #3 they seem to seat just fine. I can not fit a 0.001" feeler between the valve and seat. Although the white valve and seat seem to have black spots on them. Where the others are more shiny at the contact ring. So maybe it's leaking, probably not. Recent compression checks didn't show much difference between the cylinders. I checked the valve spring. Free height is 3". Installed height is about 2". At 2" is measure 25#. I have a Stipe 280 cam so at 1.720" the spring has 32#. I tried to take a few more pictures, but it is difficult to see. So maybe I'm leaning more toward oil burning. Maybe next weekend I'll remove a piston or two to check the piston to cylinder clearance and look at the rings.
The engine was rebuilt in 2006, with new aluminum pistons and rings. More later. Thanks
Mike, Lap the valves and check for full contact and how wide the seat is. If to wide they will leak and get hot. Scott
I second what Scott says. Valve maybe not seating square or seat too wide. It could be bent. I think the trouble is with that valve and not the other seven.
Well... could be. My aim is to check out the engine, bearings clearances et al. So I'll be looking at that anyway. I had thought of touching up the valve grind a little anyway. I certainly can try a lap first. Let you know thanks,.
If you pull the pistons out, you should replace the rings. The cylinders should be honed to rough up the surface and rings replaced. If you pull the pistons and try to re-use the same rings, they will not seat. It is almost impossible to get them in exactly the same position relation to the cylinder walls. New rings will seat in and if the bore is not too tapered or out of round, it will work fine.
"The engine was rebuilt in 2006, with new aluminum pistons and rings."
If it's low mileage since rebuild and the pistons are good, If rings look good and you want to re-use them, scuff the OD of the rings up a bit w/some fine emery paper as well as scuffing up the cylinders. They will work fine.