Shim/s under OHC head.

[garagiste]

Begging my ignorance or stupidity what purpose do shims placed between the head and the vertical drive seal mounting serve.

ie. the unit in which the top yolk of the flexi drive oil scroll runs.

Am I overlooking the obvious?

David.

[Ian Grace]

David,

Are you talking about the brass shims that fit between the lower surface of the head and the oil drain housing? These set the mesh of the bevel gears in the head by vertically adjusting the position of the vertical drive shaft/bevel gear.

[garagiste]

Thank you Ian.

Yes it is these shims that I am referring to.

I have just stripped a head that the sole way of controlling the mesh of the gears appears to be the thickness of the thrust washer "C"

Or am I still being silly.

David.

[Ian Grace]

David,

Looking at the drawing, I think you can see that the bearing sleeve supports the thrust washer and in turn the sleeve sits on the felt seal retainer plate. (These days, we use a modified plate that accepts a modern neoprene seal). And this plate rests in the oil housing, so adjusting the location of the housing under the head with shims will adjust the thrust washer, and hence the mesh of the gears.

Does that make sense, or did I have too much Merlot with my lunch?!

[garagiste]

Thanks Ian,

Drawing clear, must review the whole lot tomorrow in the daylight.

Where did the drawing come from? Are there others?

David.

[Ian Grace]

I scanned it from Blower. I'll see what else I have.

Ian

[Ian Grace]

Here's a standard housing, with the original felt seal housing in place, located by a small peg at around 7 o'clock in this image:



And here's another in my spares collection which is distinctly different:







Does anyone know what engine this is from?