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[panasonic]

Panasonic reminded me of a question regarding his original post. Ol Dangar mentioned something about the valve rework on that motor. I may have to watch again to get the terminology correct. But let me try. He mentioned the valves were not lapped. The were finished as interference. Something to that effect. Does that make sense? What is the difference?

He said that the valve seats and the valves where reground. He also said it doesn't matter which valve went where now because both seats and valves where machined (ground) I tend to agree with him on that.

They should now seat properly if the machining was done properly.No need for lapping unless maybe you are building a high performance engine.

I myself probably would have at least colored the seats with a sharpie and and spun each valve to see if I got a nice thin contact line all around the seat. To confirm that all was well with the rework.

Most lapping I have done was when taking apart the engine for some other reason, say piston replacement and while in there lap the valves to clean up minor pitting on the seats..ect. Always kept track of which valve went where.

I don't really know what he meant by "interference" in the context that he used it. Only thing I can think of is maybe he meant that valves will now bed themselves into the seats from being used (which they will) And that's is the interference he talking about..maybe?

[boscoe99]

Both the valve and the valve seat can be cut to the exact same angle. In which case it is standard procedure to lap them. Lapping is where a super fine cutting compound is placed on either/both the valve contact area or the valve seat area and then the valve is rotated/spun around the valve seat such that the compound cuts both surfaces so they are more precisely aligned with each other.

https://www.google.com/search?biw=12....0.7T_AZ0YUMDI


Interference is where the valve seat is cut at a different angle from the valve contact area.

https://www.google.com/search?q=inte...FehTXpXN3YVOM:

[99yam40]

Back in the 70s we ground the valves with one angle and then did the seats with 3 angles.
the center area was same as the valve or close to it (Memory not sure), and the outside ones to control the width of the center to control heat and puts more of the spring tension on that narrow band for sealing

[pstephens46]

Back in the 70s we ground the valves with one angle and then did the seats with 3 angles.
the center area was same as the valve or close to it (Memory not sure), and the outside ones to control the width of the center to control heat and puts more of the spring tension on that narrow band for sealing

Technically, sounds like an interference fit. From the above description. Wonder which has a longer life?

[panasonic]

Back in the 70s we ground the valves with one angle and then did the seats with 3 angles.
the center area was same as the valve or close to it (Memory not sure), and the outside ones to control the width of the center to control heat and puts more of the spring tension on that narrow band for sealing

The last complete valve job I did was more than 10 years ago, four cylinder motorcycle. All new valves as cam chain broke and bent them all. I got a valve seat cutter kit from a real motorcycle mechanic. It used carbide insert cutters on a mandrel and was turned by hand. Each set of cutters where a different angle so the seat ended up with three different angles on it as you described Yam. I then lapped then slightly with new valves and leak checked them

So I guess I did a interference valve job on that one.

It is amazing how hard valve seats are, but carbide can them no problem. Grinding them would be more precise and give a better surface finish.

[rodbolt17]

having spent many years with a valve facing machine and a seat grinder I always lapped them for a final finnish.
kinda like after you ground a crank journal you chamfer the oil holes.