PyroProblem

Is there a general rule of thumb as to when this is recommended? Like at what HP level (or is it more based on torque) should this be done?
Or is it performed when headgaskets alone can no longer hold combustion pressure?

Are there ever any cases where you would want to o-ring the head instead?

Is it always copper that is used for o-ringing?

Tyler Dirden

iTrader: (3)

There are "rules of thumb" that different builders apply to their arsenal.
Some would say that any boosted >14psi would benefit greatly.
Others would say a properly finished deck and head (exact factory specs) will hold >14psi all day properly tuned.

The head gasket is not the weak link, it's cylinder bore shifting under extreme loads and fasteners that fall out of torque spec.

Also, O-rings need to have room to be machined and most big bore 85mm blocks even with sleeves have VERY LITTLE room for o rings. They are tedious to install and possibly a weak spot at the top of the cylinder wall if detonation has it's way.
I am building two nitrous motors for severe service. Endyn's Larry Widmer assembled my drag motor and never once suggested an O ring. Just Darton MID sleeves and great finishing on the deck and head with ARP and proper torque too.


Let's hear what others have to say.

efHondefender

I know that thinner gaskets seal better and are less likely to need O-ringing. I also know that Larry Widmer (now that somebody brought him up) likes to use the thinnest possible gasket and strongly suggests never to use a thick gasket for lowering compression.

jdmconcepts

Not huge fan of o-rings. with the use of a properly installed set of Darton Sleeves, proper machine work and all the correct supporting pieces, gasket sealing is not an issue even on our big horsepower cars. we have on occasion ran a step deck only because some customers believe in it like a lucky rabbits foot.

Dark_Teg

My brother had the heads O-ringed on his 86 300zx and ran copper head gaskets. One thing is for sure, once you O-ring parts you have a hell of a time re-selling them.

PyroProblem

Was he pushing high HP or just had HG problems?
I don't think I'll ever need to o-ring my block myself as I won't be pushing that much power.
Just curious about the process and when it's needed.

PyroProblem

14 psi could cover a wide range of HP depending on the turbo used correct?

So if the sleeves shifting is what necessitates o-ringing, aftermarket closed deck sleeves should take care of that right?

What about the guys that o-ring their sleeved blocks? Is that just for extra insurance against HG problems?

Tyler Dirden

iTrader: (3)

There are plenty of guys here that run 28+ boost without O rings. They are just not chiming in yet.
Closed deck sleeves are exactly the cure and assure the cylinder stays put.

O ringing sleeved blocks is just business IMO. Why not, can't hurt, how much?

There are some though that truly run radical **** on the edge that do benefit. The O ring actually is a tad bigger than the perfectly formed groove. This allows the material to press around the cylinder considerably harder than the head bolt alone could achieve. It's like something that is not supposed to be there being exactly calculated to be there for a single purpose.

PyroProblem

Ahh okay. . That makes some sense.

Tyler Dirden

iTrader: (3)

My Golden Eagle sleeved B20 is a step deck style; like a giant built in O ring.
Sleeves are raised like .003" and aid in compression they say.
Their blocks can make 1300HP too.

Runnerdown

I don't see how the "boost" pressure is really the significant factor on when o-rings are needed. Cylinder pressure would be. There are way too many factors involved to start throwing around numbers and what's required and when.

-Surface finish on the head and block
-Sleeves used, step deck or flat?
-Head fasteners and installation
-Cylinder pressure and temperatures....and how long they are sustained.
-Thermal growth of different sleeve types and blocks.
-Drag racing, street, road race, time attack? Different application may have unique requirements.