Viton o-ring as head gasket?

[hayd3n]

k while i have the engine apart (x250) , and upsizing the headbolts,
i had the idea of machinging a groove in the head to fit a viton oring they are good for 400 degrees
,
it wouldn't be to hard for me to make a groove in the lathe with a 4 jaw chuck
but thinking as its air cooled it may be no good?

[Woodman]

I have grooved a few blocks and tapped copper wire into the groove and sealed the surfaces with Loctite 518. Works real good. Haven't done it on air cooled motors, only a couple of SB Chevys, a 308 and a 4 cyl Denco.

On my old IT175 I just lapped the head onto the barrel with valve paste and it sealed fine, and my benelli is also lapped in so can't see any issues with your motor.

[hayd3n]

I have grooved a few blocks and tapped copper wire into the groove and sealed the surfaces with Loctite 518. Works real good. Haven't done it on air cooled motors, only a couple of SB Chevys, a 308 and a 4 cyl Denco.

On my old IT175 I just lapped the head onto the barrel with valve paste and it sealed fine, and my benelli is also lapped in so can't see any issues with your motor.

interesting

[hayd3n]

no one else care to comment?

[Asher]

Make sure to add the thickness of your head gasket to the base gasket :niceone:

[hayd3n]

Make sure to add the thickness of your head gasket to the base gasket :niceone:

:niceone::niceone::niceone:

[scumdog]

I am pretty sure it was Isky that made the 'Groove-o-matic' (sounds disco eh!) for machining a groove in the top of the block, a copper wire O-ring was used.

Worked well with turbo'd motors.

The only one I knew of is no longer in the country....but it would be worth asking after one.

[FJRider]

no one else care to comment?

Do you have a reason NOT to use the factory head gasket ... ??? You already have one ... <_<

[hayd3n]

Do you have a reason NOT to use the factory head gasket ... ??? You already have one ... <_<

no i susessfully drilled out the holes in the old gasket,

+ i still need to order a exhaust gaskets and a valve cover gasket
the classic motorbike dude in nelson hasn't replied back with a price yet

[Woodman]

I am pretty sure it was Isky that made the 'Groove-o-matic' (sounds disco eh!) for machining a groove in the top of the block, a copper wire O-ring was used.

Worked well with turbo'd motors.

The only one I knew of is no longer in the country....but it would be worth asking after one.

The copper rings first used in the turbo'd motors were in conjunction with a head gasket so the copper wire would bite into the gasket just outside the bore binder. was a common mod on 2.0 Cortina motors when fitting hairdryers. Can be done on an overhead boring machine easy enough. Aaaaahhh those were the days.

[SS90]

no one else care to comment?

Bottom line is yes...... Viton Oring is perfect in this situation, many performance air cooled two strokes use Viton orings.

I am informed that over 400 deg Viton orings burn and produce a poison gas, how this is relevant I don't know.

[Ocean1]

Bottom line is yes...... Viton Oring is perfect in this situation, many performance air cooled two strokes use Viton orings.

I am informed that over 400 deg Viton orings burn and produce a poison gas, how this is relevant I don't know.

Probably a low liklihood of exposure for that application, very serious consequences if you get it wrong.

Viton: http://msds.dupont.com/msds/pdfs/EN/PEN_09004a35803ee796.pdf

Hydroflouric acid: http://www.chemistry.auckland.ac.nz/webdav/site/chemistry/shared/for/current-students/documents/health-and-safety/Hydrofluoric%20acid%20Manufacturers%20MSDS%20Sheet .pdf

[Banditbandit]

On my old IT175 I just lapped the head onto the barrel with valve paste and it sealed fine, and my benelli is also lapped in so can't see any issues with your motor.

Yeah ... done that on a 2/ motor myself ... worked fine ...

[ac3_snow]

I have lapped the head/ barrell together on one bike, I lap'd each on a bit of glass for the first bit and then together. Also on my current engine a tf125 run a vitron o ring.
When the barrel was machined he did it right around the edge of the steel liner, that way he was only machining alloy made the job much easier. Get a o ring of the right size first, before you do the machining. I have used these guys http://www.sealimports.co.nz/contacts.html but I am sure there would be a similar outfit in dunedin somewhere.

[imdying]

Flat is a relative concept, and lapping things like that is a waste of time. An engineer will have it proper flat in no time though. Lapping shit just makes it lopsided and patchy, and glass is not flat.

[TZ350]

i had the idea of machining a groove in the head to fit a viton o ring they are good for 400 degrees, it wouldn't be to hard for me to make a groove in the lathe with a 4 jaw chuck, but thinking as its air cooled it may be no good?

I originally read about using Viton O rings for head gaskets in an article posted by Dale Alexander. But I don't know of any main stream performance air cooled engine manufactures that use O rings for head gaskets but I do know a few of the Bucket boys have used Black (ordinary) Viton O rings in their air cooled 2-Strokes.

For me they have proved very reliable with very few failures. And all the failures that I have seen, mine and others could be traced to pulled studs or the cylinder loosening off in some way.

282549

I myself am looking to move back to composite head gaskets as they thermally isolate the head from the cylinder and the head runs quite a bit cooler than the barrel that way.

I think the bulk of the heat in a 2-Strokes cooling system enters via the exhaust port tract and the upper reaches of the transfer ducts at high rpm when they are exposed to hot combustion gases that enter them before the blow down process is complete.

Below are from the Team ESE thread which is gaining a reputation for very informative 2-Stroke tuning content. http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130543255#post1130543255


263916

Got the head off tonight.

263917

Doesn't look to bad in there.

263918

Carefully re checking the squish.

263914

And it looks like 1mm.

So the trick is to figure out how to take 0.4mm of the top of the barrel for 0.6mm static squish.

263915

Also checked the timing to see whats needed to get the Ex opening 80 ATDC and the main Trans opening 116 and sec 114 ATDC.


Ok I got the chance tonight to find out what went wrong on the dyno last night.

254567 254568

Blown head gasket ("O" ring) as I suspected.

254570 254569

The piston has been just touching the head

254571

The piston itself looked good and the ring was still free in the grove.

254566

The culprit is the hand made gasket on the right, it compressed down to much, I expect its compress-ability allowed the combustion pressure to spit the "O" ring out. I replaced it with an alloy plate which should give a more reliable stack for setting the squish clearance and give something more solid for the head to pull up against.

[F5 Dave]

. . . but I do know a few of the Bucket boys have used Black (ordinary) Viton O rings in their air cooled 2-Strokes.
. . .
Erm, Black is usually Nitrile & is just fine for outer gallerys. You might get away with them but all the Viton o-rings I've seen are dark green or brown.

[TZ350]

Erm, Black is usually Nitrile all the Viton o-rings I've seen are dark green or brown.

Properties of O rings. http://www.sealanddesign.com/category/Rubber-Compounds-O-Rings/462.html

The common ones, Viton Nitrile and EPDM can all come in black as carbon is the filler of choice, other colors mean different fillers have been used to give the O ring particular properties.

The standard commercial V1000 Viton O ring is black. http://www.marcorubber.com/viton.htm also lots of other useful info like groove design and material selection.

282609
Page 2 of ProMinents tec sheet talks about "the bounce test" which is the easiest way to tell black Viton and EPDM O rings apart.

ESE imports, distributes and supports the full range of ProMinent water treatment equipment throughout NZ. http://www.ese.co.nz/