O-rings again

[JHertzman@domain.elided]

I received an off-digest note from an old-timer who lurks but, for valid 
reasons, choses not to participate directly.

"What no one (so far) has mentioned is that while the o-ring supplied for the 
2600 has the same dimensions as those for all the 4-cyl in-line Alfas the 
2600 o-rings were also available in non-distorting Delrin. I no longer have 
my complete Alfa library but am quite sure these were available under an Alfa 
part number from ARI. I still have a dozen or so of these in stock (not for 
sale!)  I've used these on every single 4 in-line engine I've built since the 
late '60's without any failures and without any evidence of distortion when 
our racing engines were being routinely rebuilt.

"With proper installation and correct initial and follow-up torqueing the 
Delrin rings will flatten to match the surfaces of the block and head 
providing superb sealing but will not distort into the "@" shape typical of 
the OEM o-rings.  They are absolutely superior to any of the suggested 
alternative o-rings, in my opinion and experience, and obviate  the need for 
any additional "shape-retaining" elements which reduce the inside diameter 
(and flow volume) of the galleries. These o-rings have a "rounded donut" 
cross-section rather than being flat-cut. Delrin is "self-lubricating", 
essentially chemically inert and quite dimensionally stable. As you know, it 
is commonly used for suspension bushings.

"For those who wish to use the brass tubing method Fred mentioned, I used 
that method with acceptable success.prior to discovering the Delrin rings The 
tubing in appropriate size is typically available in any well-stocked 
hardware store if that method is chosen but only Viton o-rings should be used 
in this application. (These are typically sort of a chocolate brown color.)

"Even if you can't find an OEM P.N. in your 2600 library for the Delrin 
o-rings, you might want to mention them on the Digest. I have no doubt that 
they are available in appropriate size from any number of industrial 
suppliers and perhaps one of the more "sophisticated" Digesters could locate 
a source in a current industrial product catalog."

End of quote. Interesting, in my opinion.

John H.

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