Roll pins, not Roll Tide: Seeking technical advice

[La Voce]

I'm in the middle of rebuilding my Alfetta's 2 liter. When I removed the head I noticed the six oil passage roll pins barely protrude from my engine block (about 2mm), just enough for the pin tops to be flush with the top surface of the head gasket I removed. The old rubber O-rings that were around the pins were barely secured by them, and were easily brushed loose with my finger. I read on the Centerline website that the pins should protrude about 2mm above the gasket when installed. I tried grabbing one by gently tapping an extractor down into its hollow center and twisting it out but it refuses to budge. If their height is that critical then I am tempted to leave their extraction and insertion to a machine shop, as one gouge on that mating surface by this rookie and I'm in trouble. What's the risk if they don't protrude slightly above the head gasket when I reassemble?
Thanks

[Andrew]

I think they'll be fine. If they stick up too much, the head will just push them down anyway. If they're protruding more or less the height of the o-ring, they should work fine when locked in place by the head and the circumference of the o-ring cutout in the head gasket. You still want to be very careful on assembly to make sure they're in place properly.

Andrew

[La Voce]

Thank you, this confirms what a local alfista just told me tonight...think I'll leave them alone.

[George Willet]

Jim: the purpose of the pins is to restrict the oil flow to the head/cam area, not to locate the o-rings.

Assembly tip: I use Chevy valve seal square cut o-rings instead of the round cut o-rings. They hold up better. Just make sure they are carefully fitted into the holes of the gasket during assembly. They are available from any autoparts store in bulk.

[Andrew]

Most of the Alfa parts places will include Viton or other modern o-rings with the head gasket automatically, or for a small extra price.

I'm not sure I agree that the roll pins are just to restrict oil flow. I have seen so much written about their use in locating the o-ring, and have found twisted, pretzelish o-rings, doing no sealing at all, in engines with no roll pins. Maybe one of those things were there are multiple perspectives.

Andrew

[George Willet]

Hi Andrew:

Re o-rings: I had to do a lot of research on o-rings and their design and function when I started the business of rebuilding thermostatic actuators about 20 years ago.

An o-ring is effective as a seal because of mechanical containment on the top, bottom and outer diameter, and held in place by the oil pressure on the fourth side.

[101/105guy]

This is from a 1600 Super motor......

Roll pins would have been a great idea !!

[Andrew]

Yes, this is just the kind of thing I've seen.
Andrew

[Alex]

For those of us in Europe where Chevy V8s are not so common, would someone please get an accurate measurement of these O-rings? I/D, O/D and height. Prefer millimetres but good old Imperial is fine too . Thanks!

Alex.

[George Willet]

It appears to me that these O-rings shown are too large in diameter for the application, and/or they were not compatible to engine oil and heat and swelled up..

Not all O-rings are made of oil compatable material. The O-rings I used for the thermostatic actuators rebuilding had to be specially made to be compatable with the actuator and engine fluids.

And before any one asks what the actuator fluid is, I'll tell you. Alfas being an Italian car, the actuators use olive oil and vinegar.

[George Willet]

Alex, the O-rings are the valve stem seals for an early Chevrolet V8. It would seem to me that there are lots of them in England and the parts houses or repair shops would have them, as some engine overhaul gasket sets come with the o-rings as well as the "umberella" style valve seals for later engines.

Asking for the seals by dimension would not necessarly get the correct seal material, rubber seals would deteriorate over time and look like the ones in the photos shown on this post.

If you can't find them there, email me direct and I'll put some in an envelope and mail them to you. They only cost pennies each.

[papajam]

Alfa Technical Service Bulletin 01.07.2 dated June 1977 says that the rollpins should stand proud of the deck by 1.5mm (0.060").

And, like George, I use the Chevy square cut o-rings.

More about o-rings from both George and me a bit later...

[DaveC]

Quote:

Originally Posted by George Willet Jim: the purpose of the pins is to restrict the oil flow to the head/cam area, not to locate the o-rings. Assembly tip: I use Chevy valve seal square cut o-rings instead of the round cut o-rings. They hold up better. Just make sure they are carefully fitted into the holes of the gasket during assembly. They are available from any autoparts store in bulk.

[yvesmontreal]

If you use roll pins, make sure they are indeed ROLL pins and not SPLIT pins. I have seen one engine on which oil pressure spread the split pins open ever so slightly, which in turn distorded the o-rings. Not quite the desired effect.

A friend of mine used to install short pieces of 3/16 brake line instead of roll pins. Just another idea.

[DaveC]

Quote:

Originally Posted by Alex For those of us in Europe where Chevy V8s are not so common, would someone please get an accurate measurement of these O-rings? I/D, O/D and height. Prefer millimetres but good old Imperial is fine too . Thanks! Alex.