Fronkenstein

Hi 928 enthusiasts. I would like to know if anyone here has thought about or tried to machine their heads to accept a high temperature o-ring to replace the ridiculous paper gasket that invariably gets sucked into the intake port with age. I have seen this on two engines in immediate succession.

I have two sets of heads in the shop and am contemplating on programming the CNC to cut them for -224 STD o-rings made of silicone. These are the same time tested o-rings that Caterpillar and others have been using with 500,000+ mile success.

Would love to hear any feedback.

Pete

Leon Speed

No paper gasket on the 928...steel enforced rubber/synthetic.

Fronkenstein

That is not what I just pulled off my 1978 ROW

Fronkenstein

Perhaps two engines with sub-standard gaskets? Quite a coincidence.

Lizard928

78-85 use paper gaskets, though I've never seen one sucked in or broken without the runner being removed.

Fronkenstein

Two ports on one engine and one on the other. The Victor kit doesn't do much to improve on the situation either. Anyone think I am crazy o-ringing the heads? The CNC set up is pretty simple. We're talking a 1.500 opening that is easy to reference off of. We have a total seal surface area of .350 to work with making it a reasonably simple mod that will take all the worry out of the seal. Drop the o-rings in place, put the tubes on, bolt them down - perfect seal. Thoughts?

Lizard928

It's a good mod if you have the heads off and tools, but for the average car, not worth it.

123quattro

That's an odd failure Generally paper gaskets get really stuck to the mating surfaces.

Fronkenstein

BTW I am looking for some replacement exhaust valves for 1978 928 if anyone can help. Right now I need two.

Otto Mechanic

Not I certainly, I was asking myself exactly the same question day before yesterday.

Take a look at the 944 3.0 turbo threads (start with the 3 Liter Turbo Registry), you'll find references to machining the heads to accept inset copper gaskets, there's a name for them, something like "crossfire" gaskets. They aren't on the intake side, on the actual piston head. The increaed combution pressures on the turbo 3.0 builds almost require them. Can't see why the same approach wouldn't work to improve the 928 intake gaskets.

I know this only because I happen to have a 2.7L head orriginally planed for a turbo conversion on my 944S2. There are quite a few people who swear by it.

Otto Mechanic

Hmm. I've replied to the wrong thread. Same topic, different thread. Sorry for the confusion...

--------

Well, I'm in a quandary now; I've had at least 3 well respected builders including Greg, Stan and Leon say the metal gaskets are the way to go, and while I've been toying with the idea of designing my own solution to this problem I'm short of time. Usually I wouldn't mind experimenting but I have a deadline facing me, I need to get the car out of my current shop and down to the new one before May 1st (closing escrow) and I also need time to move my tools and lift before then.

So, I probably don't have time to mess with it.

Folks have been smirking a bit about why I take the intake off all the time, and I sort of get that, but the reason is I make incremental changes to the car in addition to the normal "Oh **** I've got coolant all over the floor" moments. I know for a fact I'll be taking the intake off yet again in the future to do some work under the cam covers. It would have been nice to do that this time, but like I said, time pressure. Hope that satisfies the inquisitive?

belgiumbarry

i never seen a problem with the paper gaskets , perhaps it was more due warped runner flanges.
Mostly they are even difficult to remove , baked to the heads or runners.

Otto Mechanic

They certainly are that. It took me days to remove the last vestiges of the old paper gaskets when I finally did it. They aren't that hard to get off the runners since those can be resurfaced easily, I used 320 wet/dry on a polished granite slab to clean up mine, but getting the residue off the aluminum block is a challenge.

Mine were so well baked on I didn't even notice they were a replacement part until my fourth removal of the runners. I should have replaced them long before, but I literally didn't even see them. No excuse, I should have known, I just wasn't looking. I didn't have vacuum problems until I replaced the paper gaskets. My theory is they need to be correctly torqued, then given time to settle and retorqued later. I don't have time to do that so I bit the bullet and bought the metal gaskets.

I've switched to the '87 style metal gaskets but I haven't finished the rebuild yet so can't say they fix my problem with any authority. I should know more in a few days.

rdomeck

If you did O-rings for this gasket surface, I would put the O-ring in the runner surface. Would be a lot easier to replace the runner if your CNC crashes or if for some reason the O-ring didn't work. Once you cut the head, you are committed! I used to build race 911 engines, as well as street engines. Mostly GT cars for PCA on the race side. Even the GT5 cars we would use a short runner with an O-ring on the bottom that matted to Lectron carbs. Ran this set up on a GT2 car as well.