O-Ringing The Cylinder Head

Wheelman-111 · Post by **Wheelman-111** » Mon Apr 13, 2009 3:21 pm

Greetings:

Polini kit re-uses stock head and suplied Polini head gasket. Unfortunately replacement gaskets are difficult to locate and of course are not free.

Werx or BT once told me their heads were grooved for o-rings. I found a machinist ("Ol' Crusty") who can cut the groove, but my questions are:

Where to cut the groove? (48mm from center of plug threads was suggested by Crusty, who thinks it needs to make contact with the "steel liner" of the cylinder - but I don't think the Polini bore has one...)

How deep and wide is the groove?

What material to use for the o-ring?

Source for said o-ring?

Thanks for any & all help.

Kenny_McCormic · Post by **Kenny_McCormic** » Mon Apr 13, 2009 3:48 pm

Get some copper flashing and make a gasket.

scooterwerx · Post by **scooterwerx** » Mon Apr 13, 2009 4:02 pm

any industrial seal place should have em, the one on my malossi head is about .050 thick, and is just barely on the outside of the combustion chamber, maybe .030. viton is the stuff to use, designed for use in high temp and high pressure applications. there is no "steel liner" on a cast iron cylinder. as far as groove depth, id go .015 less than what the o-ring is, so the o-ring is compressed .015. look up the machinist's handbook, im sure there is a spec in there for this. that much has worked well on everything ive built so far...

ALOW1 · Post by **ALOW1** » Mon Apr 13, 2009 4:15 pm

Buy an after market head with the O ring in it.

Wheelman-111 · Post by **Wheelman-111** » Mon Apr 13, 2009 4:25 pm

Greetings:

Thanks Werx! Details like that are very useful.

SO... Machinist's Handbook? Something Google-able?
Viton 0.050 ring, Groove around 0.035 deep means 0.015 compression?

Perhaps it all needs a dab of hi-heat Permatex to hold everything in place on the first assembly?

Post by **noiseguy** » Mon Apr 13, 2009 4:32 pm

You could probably just use the Permatex in absence of a head gasket if your head is flat and you have the clearance.

Wheelman-111 · Post by **Wheelman-111** » Mon Apr 13, 2009 4:51 pm

Greetings:

Noisy submits:

You could probably just use the Permatex in absence of a head gasket if your head is flat and you have the clearance

Hey, HEY, HEY!!! Let's not get personal. I am short, and I do have a flat head, but let's limit the discussion to engine parts here.

Actually I don't trust my measuring tool kit - pointy stick - and Permatex for such a critical function. I hear Malossi kits come with a Factory o-ringed head, and by golly I want one too!

I just need to be able to tell Crusty the Machinist what to cut, where, and what to stuff in there when he's done.

Kenny_McCormic · Post by **Kenny_McCormic** » Mon Apr 13, 2009 6:16 pm

All you gotta do is lap it flat and use some permatex on it, I think they make a special kind for heads and high temp stuff. Either way you go it will need to clearance check without a gasket(o ring will not act as any spacer).

scooterwerx · Post by **scooterwerx** » Mon Apr 13, 2009 10:31 pm

theres gotta be a machinists handbook online somewheres...google fer sure.

AustinS · Post by **AustinS** » Thu Apr 16, 2009 4:23 pm

I ordered some orings for my carb from http://allorings.com and they have a material guide here http://allorings.com/material_selection.htm

Make sure to get something that isn't going to disintegrate on contact with gas.

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