[alfa] O-rings (was: Oil Leaks on Alfa Four)

["John Hertzman" <johnhertzman@xxxxxxxxxxxxx>]

In AD9-1056 Russ Neely writes "In days of old, the O rings would not 
retain their shape - they would turn to a pretzel shape.  Then someone came up with the idea of putting roll pins in the passage where the head joins the block. Plus a material called Vitron came along.  Vitron O rings plus the roll pins to keep them round seems to have solved the problem on most late model Alfa four cylinders. I am not sure exactly when Alfa started putting the roll pins in at the factory.  But I am pretty sure all L Jetronic spiders had them, so the change may have been about 1982."
 
There was an extensive thread on the O-rings, roll pins and related topics from AD7-621 (7 Apr 1999) through AD7-637 (Wed, 14 Apr 1999). Lots of interesting stuff, from many prime sources I don't remember seeing recently. I had nothing original to contribute, but did add some ancient history and some notes from Fred and from the serious lurker I used to call "the oldest rat in the Alfa barn." Herewith parts of a couple of posts:
 
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Alfa's original approach to sealing the oil passages from the block to the head had been the use of neoprene O-rings all by themselves from the first Giulietta; they worked very well except when they didn't. They were reportedly prone to displacement, premature collapse, and even to being blown through the oil passages and up into the cam bearings. My best information (always subject to amendment by anyone who has better sources) is that roll-pins were first used to keep O-rings from wandering in 1964 on 2600s by Gaston Andrey in Framingham, Mass.; that Alfa Romeo soon 'allowed' dealers to adopt the procedure for cars which were still under warranty without voiding warranty; that by 1971 the factory was supplying them for 2600s but not for the fours, and by the late seventies they had been adopted for all. "Alfa Owner" Tech Ed Joe Benson asked several questions of ARI in January 1978 about the then-new roll-pins and never got an answer. Exactly when they were first used in production I do not know, but they show up as part # 02160.10925.00 in the Catalogo Rapido Ricambi covering all USA-version Alfettas from 1975. So the short answer to Rich's question is yes, in '76 for sure.
 
Rich's question #3 was "Should I not use roll pins at all and get some of the tiny rings Alfa Ricambi sells that are slightly smaller than the O-rings and fits into the O-rings to maintain the shape of the O-rings?"
 
At a tech session in April '92 Peter Krause was showing the tiny aluminum rings, which seemed pricey at the time; I forget the exact price, but my impression is that it was about $20 a set. Peter said he likes it because it offers less restriction to the oil passage, and he also was turned off by the irreversibility of the roll pin- easy to get in, very hard to get out. I asked whether he has ever seen evidence of head damage because of roll-pin oil passage restriction; he said no. So- it seemed to me to comes down to whether an undeniably neater way of doing things is worth an extra $20 or so, and also whether there were real advantages beyond conceptual purity. In my next letter to Fred Di Matteo I asked had he an opinion? Had he ever seen evidence of head damage because of roll-pin oil passage restriction starving the cams?
 
His quick reply enclosed a sample of his solution, which he had written about many years before and I had missed- or forgotten. In any event, it bears repeating. Let him tell it:
 
"The idea of using the roll pins to contain the 'O' rings is fine but the better method is to use brass tubing found in hobby shops which comes in various sizes. I believe they come in lengths of 12" or more. Cut to length, it makes the perfect solution for unrestricted oil passage. The existing oil holes in the cylinder block are drilled out larger to take the OD of the tubing, which is not very much larger. I like to match the oil holes in the cylinder head to the block holes and to allow the sleeve to enter the cylinder head by perhaps as much as a sixteenth or so. All that is needed is the right size drill in a drill press and a little common sense. -- Herb [Bridge] made me an extension so I could reach down past the cylinder head studs--" As for head damage because of oil starvation, that which he had seen "might have been due to other factors a careless owner might not admit to--" but he thought not to roll pin restriction.
 
The sample Fred sent miked .218" OD; the nearest handy hobby catalog lists telescoping brass tubing with .014" wall in twenty sizes including 7/32" which should be .21875", close enough. That catalog sells ten 12" pieces for $6.50; in the length Fred sent, it works out at about two cents each. 
 
The only quibble I could think of would be possible corrosion with dissimilar metals- I expected it might be there, but slight; if it was a real problem I doubt that it would have gotten by Professor Bridge. So I wrote it up for my chapter newsletter.
 
Joel Hailey, then Technical Advisor for International Auto Parts and later at Centerline, responded with a counter-argument. He questioned 'why?' since he knows no evidence of oil starvation from roll-pin restrictions, questioned the corrosive combination of aluminum and brass, and was concerned about aluminum shavings winding up embedded in the bearings. He ends with "I don't believe in creating a problem where there is none. Alfa Romeo recommends the roll-pin and O-ring technique, the validity of which has been proven by experience in the field. In this case I must say, 'if it ain't broke, don't fix it'."
 
The possible problem of corrosive linking of dissimilar metals with brass or copper in aluminum  had occurred to me, and was mentioned in my original note. Water is a much better electrolyte than oil, though, and Alfa tolerates a copper radiators and oil coolers and many drain valves and other fittings, as well as bronze valve guides, so I don't feel spooked by that. The question of where the shavings go is a fair one; I assume the answer isn't harder (or the consequences worse) than for other shaving-producing operations. 
 
The question is probably usually moot by now; Fred came up with his variation when he was still doing first head gaskets on cars built in the sixties and early seventies, and there are probably few old engines which haven't been pinned by now - but there are some. (I know I have a few-)
 
Jaap Bouma's response to Rich's questions establishes that Alfa isn't disturbed by knocking the roll pins down into the oil passages. Rich's question #2 had been "Should we try to remove the old ones with an easyout? (This seems like a bad idea since the spring steel the pins are made of will probably fracture and drop shards of steel into the sump, but I have to ask anyway.)" Into the sump wouldn't be bad, given magnetic drain plugs, but there is no way I can see to get to the sump; the oil gallery has the oil pump gears at one end and bearings at all the other ends. 
 
I like both the aluminum ring and the thinwall tube, but the roll-pins seem to work quite well enough. In Rich's case, with the roll-pins not protruding, I would probably go with the aluminum rings.
 
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I received an off-digest note from an old-timer who lurks but, for valid reasons, chooses 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.
 
Cheers
 
John H.
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