Understanding Billet/Oring Heads

[Spoony]

I'm try to get my head around Oring heads as I've got two Riva Girdled heads but have questions.

I bought a second head with good domes off ebay as my original has questionable domes (very thing seating lip, and surface has been sanded some due to damage).

Anyways It's my understanding that the orings only seal water.

If this is the case the orings shouldn't show any signs of heat damage. With the newer head this wasn't the case

After only 1 1/2 tanks there is heat damage, and yes they are viton rings.

Compression with Orings on the new head is around 150 and without orings only 90!!! This tells me the dome lip is not seating

Testing with the old head gives 150-160 (depending on cyl) without orings, and maybe 5-10psi more with orings.

Should the compression be no different without orings? I thought this was the case, or a small rise in compression (due to very small seapage?) acceptable?

Running a straight edge across each head, the old head seems to have the domes slightly raised from the rest of the head surface. The new head seems the head surface and domes are on the same level.

Cheers.

 

[chriselmore_1]

So you are running an o ring head with no o rings?

 

[Tanman]

I guess the theory behind it isn't as important as just running what needs to be ran. I would orings reguardless what the compression sealer surface is. It is grooved to run o rings, run them or you would need a head gasket. With would not make it an o-ring head. Just thinking aloud here with ya

 

[grezzmky]

I dont think he is actually going to run it without orings. He is just saying that compression should not rely on the orings ......

 

[Spoony]

I dont think he is actually going to run it without orings. He is just saying that compression should not rely on the orings ......

Yep yep thats correct, as such i'm trying to work out why the newer head has so little comp without them. Hi temp viton orings were as burnt in 1hr as std orings on the old head in 20 which can't be right.

No oring can handle combustion temps and my thought was they only hold back water.

I'll have to get some dig verners i guess and make some precise measurements.

 

[grezzmky]

What is that stuff you use when building a car motor that you scheck bearing clearance with. Its like a spigetti noodle made out of puddy you put it on tourqe the parts down and then measure.

Damn, I just typed all that then remembered its called Plasigauge. Autozone carries it

 

[ATS_Scott]

The o-ring does seal combustion pressure, but it is mostly protected by the edge of the dome. Older domes can wear and won't seal the combustion pressure. If the domes wear, you may be able to lap the head shell, so the dome has less clearance and the o-ring can do it's job.

 

[orangefinger]

I once had a ada dome >> the o -ring groove was to big and the o ring did not seal either, it was a rare thing but took me a while to figure out.check the grooves to make sure they are the same size

 

[dave916]

Are the two domes from your old head the same cc as the two from the one you just got?

 

[Spoony]

So the Oring does seal some combustion presure. I would think this would be minimal due to the temps involved.

I just pulled apart both heads and cleaned up with 'seat' in the body behind the does on the old head. I tore out the old stuffed oring and scrapped back all the muck and corrosion, same on the old domes.

I seems now on both heads the domes are pretty much flush with the head body. I haven't chucked it on to comp test without orings but I can only imagine it would have dropped.

It seems mainly the old messed orings and corrosion was what made the old domes/head protrude so much. I can only guess this is not suppose to be the case.

The new body and domes are in good condition, domes like new. The old domes are quite warn witn the seal 'lip' 1/2 as thick as the newer domes (my guess is these old times were once used on an 83mm bore or something).

The gap for the oring is consistent.

I tried measuring using digital verniers differences in the dome seat the face, body seat to face etc. It's hard to get accurate one such super small tollerances but all seem to be within 0.05 of a mm.

 

[kevbo]

You have to lap the cylinder deck and head for a good seal. The O-rings are for water not cylinder pressure. Its uber important that the surface of the domes are perfect, no scratches or dents. You will know if the dome is leaking by the pisser stream. If its broken then its leaking. O-ring heads are not that great on Yamahas, they should use a crush gasket instead.

 

[Spoony]

The cylinder has been decked/lapped, and the domes lip surfaces are very good. I ran them over a flat surface with some fine wet & dry paper ver very lightly just to nick off anything imperfect.

Yes I had exhaust gas out the pisser before, oring was busted.

Im thinking might be easier to get standard head, get it shaved and the domes cut and be done with it. ?

Other mods
Dual blackjack 46's
R&D Wet pipe

I think it's also ported, but raised ports. Anyone know the stock internal port height for 61x cases?

 

[tshank123]

Im having the same issue as you on my SJ. Glad you posted this up. Mine is an ADA also, its the only o-ring head Ive ever had this problem with. I figured I needed to have the cylinder decked, but I honestly cant find anything wrong with the surfaces of the head, cylinder, or domes.

Kevbo, excuse my ignorance but what do you mean by "lap" the cylinder and head? I tried licking it but it just tasted bad and didnt solve my problem.

 

[tshank123]

bump

 

[easyrhino]

http://en.wikipedia.org/wiki/Lapping


My cylinder sleeve is pressed below the cylinder casting (a few thousands). Lapping would make the cylinder casting flush with the sleeve. A skilled automotive machine shop could do it.

And IMO it would take precision and <1 micron finish to seal without an O-ring. The Space Shuttle uses O-rings in it's booster rocket to seal hot gases at high-pressures.

 

[tshank123]

http://en.wikipedia.org/wiki/Lapping


My cylinder sleeve is pressed below the cylinder casting (a few thousands). Lapping would make the cylinder casting flush with the sleeve. A skilled automotive machine shop could do it.

And IMO it would take precision and <1 micron finish to seal without an O-ring. The Space Shuttle uses O-rings in it's booster rocket to seal hot gases at high-pressures.

Thanks for the definition.

About your second comment, why then are we literally burning up these o-rings then? I always thought the theory was that the surfaces provided "most" of the seal, of course not all of the seal though.

 

[Proformance1]

This makes me wonder about the Pro tec rec head, I just bought for a spare motor??? Only an oring around the cyl and no place else. Good, bad??? Use it, don't use it?