roll-pins

[JHertzman@domain.elided]

In AD7-621 Rich Hirsch asks several questions about roll pins (roll pins? 
roll-pins? rollpins?) His #4 was "Were roll pins factory installed in engines 
in '76?"

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 now 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.

John H.
Raleigh, N.C.

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