Chris White

Now that I have recovered from a week long sick out (step and flu) I can’t help but feel the need to toss several opinions out –
The stock head gasket is not a ‘safety fuse’. You can easily completely destroy your engine regardless of what you have as a fuse! I have a block with a cylinder split top to bottom that had a stock head gasket. You detonate it nard enough it will break.
If your tuning is bad enough that you are bending/deforming/ braking stuff don’t worry about the head gasket - worry about the tune!!!!

And one more thing about Oringing – Cometic recommends against it (you have heard that already) and your head will not work with a different diameter piston. Heads that have been O ringed for a 100m bore will not (usually) work with a 104mm bore set up. I have run into this several times (much to the disappointment of the guys with tweaked 100mm heads!).

Porschefile

They both seem to work just fine. I only ever see Raceware stuff with the Porsche crowd. The one thing I like about ARP and why I would use them myself is they provide more info then you could possibly want to know about technical and metallurgic issues related to their components, plus their stuff has been proven in a wide variety of motorsports for years. Judging by what I've heard from Raceware users, it sounds like you really can't go wrong either way.

Hope you feel better Chris. Seems like everyone down here has the flu right now also.

hosrom_951

Just to ask, how does a machine shop install o-rings?

Does the shop cut grooves 2mm deep and press fit the o-rings? then (if required later) the or-ings would be pressed out if the head needs to be decked in the future?

Van

I used stainless steel wire 0.041" in diameter to make the o-rings. We cut the o-ring groove in the head 0.040" wide (for a 0.001" interference fit) and cut the groove 0.038" deep (so the o-ring would stand 0.003" above the surface of the head).

For what it's worth, this was for a copper head gasket. These measurements may not be the same for standard construction head gaskets (stock and wide fire ring).

I had also done all of the calculations -- calculate the area of the o-rings that touch the head gasket, and how much copper material would have to deform to make the proper seal giving the clamping force of the proper head stud torque.

It's all a ballance of the amount of deformation you want (height of the o-ring and material of the head gasket) vs the area of the o-rings (diameter) -- since clamping force is a constant.

If not planned properly, you'll either be lacking on sealing the combustion chamber (which is the point), or you'll be lacking on the ability to seal the oil and coolant passage ways.

billthe3

Very informative thread! I'm in the process of doing the hg and was told by my shop that o-ringing the head is a good idea. What kind of place should I be looking for to do this kind of work? I'm sure my shop will be able to recomend a place to take the head, but would it be worth it to not even look at the local shops and simply send it to lindsey? I'm also planning on having the valves done as preventitive maintenence since the head is already off, if that affects where I go to get work done.

Just to reiterate what has already been said, o-ringing the head and using a widefire gasket with stock studs should be fine for a decent amount of boost and a good length or time assuming I have the proper tune? Or would I be better with a MLS gasket and/or aftermarket studs?

MM951

I read the topic but I am not clear on the procedure for decking an o-ringed head. The cylinder head that came on my 951 is o-ringed and the machinst at work does not have experience with o-ringed heads..says he does not know how to check the orings and does not know if he can deck the head.

The car had a stock head gasket on it and the block didn't was not modified at all. Should I be able to just put the new head, leaving the o-rings in place on with a widefire head gasket provided its straight or do they need to be replaced?

Van

With precision spacer blocks (or even a set of parallels) and a straight edge, your machinist should be able to determine if the head is flat. If it is, I would leave it be -- why fix something that isn't broken?

I assume the block is still in the car? If so, you can check it with a straight edge, too -- if it's out the car, your machinist can check that, too.

If the head does need to be decked, then yes, the o-rings will need to come out, the grooves will need to be made deeper (since you'll be taking material off the head), and finally new o-rings will need to be made up.