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Seals for cylinder head ports

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I'm making up the induction tubes for my radial from 5/16" OD x .035wt aluminum versatube. The trumpet flaring profile is coming out reasonably consistent. They need a bit of dressing but in the end have ~ 0.030" flat on the end to match the internal port counterbore face. The nut seems to push against the tubing flare OK. Initially I thought I found a good size/thickness/durometer combination of O-ring. But after closer inspection it seems iffy. The ring wants to kind of flow inside the trumpet. But I noticed that a dummy flat washer I made from aluminum fits very consistently, so I'm thinking the issue is more about the rectangular section vs circular O-ring shape & durometer/hardness.

I tried looking online for something off the shelf that might work, but this is an odd ball size, about 11mm OD x 6-7mm ID x 1-2mm thick. I don't have a lot of wiggle room thickness wise. I thought about buying a stick of teflon & machining my own washers to size. But would that material be soft enough to sufficiently deform for gas seal with typical tightening pressure? I cant get too rammy tightening these nuts, the aluminum threads are kind of delicate & the weird entry angle. Mostly I don't want air leak messing up the inlet mixture. Max temp would be the head itself.

For the exhaust side I was thinking copper for higher heat. I'm less concerned with leak there but maybe teflon would serve the same purpose there?

Any recommendations or ideas?

Head port closeup. Sorry for the mess, deburring all the sharp edges with rubber abrasive

Maybe partially answering my own question. I made some washers out of UHMW & nylon today from scrap rods on hand. Both passed the air seal test. So if teflon hardness is about the same or maybe ideally a bit less, I should be good to go. Its rated at 327 deg C. Also didn't realize was the same as PTFE, so that widens the shopping scope. Have not ford a cheap supply for ~ 0.5" diameter stick.

What about a thin copper washer, seals spark and glow plugs OK and won't soften when your head gets hot.

Roger B:
If you can anneal the tubing (250C in a domestic oven??) maybe you won't need gaskets at all  :headscratch:


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