500/550 Cam cover seals. Pucks.

[Seabeowner]

What's the obvious reason (that I'm obviously missing) that the 500/550s have the 6off sealing washers top of the head/cam cover? The US call them pucks. Why not O rings as there is only a small blind space in the cam cover above and access to head nuts below.

[Colonial-Clive (yindi)]

I missed one out on rebuild and leaked oil everywhere.

[Trigger]

What's the obvious reason (that I'm obviously missing) that the 500/550s have the 6off sealing washers top of the head/cam cover? The US call them pucks. Why not O rings as there is only a small blind space in the cam cover above and access to head nuts below.

Please try it  I have and it gets a bit messy 

[Bryanj]

No groove, only a flat surface so O ring migrates

[Seabeowner]

It dawned on me as I woke up this morning. It would need a location in the cam cover or some other form of internal support..and this was the easier option.
The 500 aftermarket gasket sets often seem to come with the pucks, but never found a 550 one with them. Annoying.

[Bryanj]

The only difference between 500 and 550 gasket sets is the clutch cover gasket

[mickwinf]

surely the head and base gaskets differ?

[Bryanj]

Nope mate same part numbers, maybe VERY early 500 head gaskets were a bit smaller hole but when you look at max overbore on 500 to standard 550 there is little difference and the "Fire ring" in the gasket still seals on the liner top