Head gasket mod needed

[avdwaal1]

I have a 89 C4 engine that I知 rebuilding. This year does not have a head gasket and would like to get my heads/cylinders machined to accept the head gasket. I知 having trouble finding a machine shop who can do this. I have tried champion engines, Hollorans performance and Ollies. I知 willing to ship.

Thanks,
Arthur

[john walker's workshop]

New P&Cs and heads flycut to match the new cylinder shape.

[PeteKz]

Why do you want to do this? Porsche went to no head gaskets on the Turbos first, so it should be good enough.

[stownsen914]

I'm also wondering why you want a head gasket. Why not have the heads surfaced?

If you have a special requirement for a head gasket, I understand Neil Harvey (Performance Developments) has a solution for 911 engines. Look him up here on the forum.

[porschedude996]

There was a problem that the factory addressed with cylinder/head leaks. There were some, very low percentage, that seeped and the junction was wetted. From my poor memory, I think that it would be addressed if there was a drip of oil, not just a trace of a leak. Good clHead Studs and proper surface condition is the best an the easiest.

[Neil Harvey]

Originally Posted by avdwaal1

I have a 89 C4 engine that I知 rebuilding. This year does not have a head gasket and would like to get my heads/cylinders machined to accept the head gasket. I知 having trouble finding a machine shop who can do this. I have tried champion engines, Hollorans performance and Ollies. I知 willing to ship.

Thanks,
Arthur

I believe this is one the best reliability features you can add to these engines. I have never seen one Porsche air cooled engine that did not leak. Every engine I have had in for rebuilding, they all have that tell tale oily mess on the exhaust side between the heads and Cylinders.

Don't get confused that our solution is the same as the "Niresist" ring add on. This was originally done in the early turbo days. Engines were mechanically fuel driven and also in the early days of EFI, the throttle would be closed, fuel supply limited, ignition timing barely retarded, but the boost never dropped. The caused massive detonation that would torch a hole right through the joint between the heads and Cylinders.

Our solution is about sealing the chamber completely and to stop any metal transfer between the head surface and the top of the cylinder.


One of the attached images shows an engine with over 20 years service with no signs of leakage.

[MoreGAS]

What you may have heard of was the updated cylinder head sealing arrangement that came on all 3.6s post 91.5 M/yr. The fix for preventing leaks of oil both ends of the cylinders, and perhaps sealing compression a bit better was to have a much wider sealing surface that goes out past the studs, more area but also not "levered" when tightened down cold, one can imagine how deformed the head can get under boost and 350+ F degrees(which we see on all streeters on moderately warm days all the time) , they simply do not stay flat even when new, and this is the beginning of leakage. You can have your heads fly cut adding this late design, but there is no modification for your cylinders, these need to be changed out to later design & top features. Then you can use the stock gasket that is used on 3.6 and 3.8 engines, even the race 3.8 engines used this arrangement. This is a sensible fix that is serviceable for a streetcar.

If one were to use what Neil pictures it still doesn't solve the levering issue w the heads tqe'd out beyond the sealing surface. Sidenote, 20 years of service and the heads shown have no carbon, no heat trace discoloration at all, and mating surfaces look just cut? What? There are many schemes like this to try and create a better sealing surface on these aircooled engines, we have tried many w varying degrees of success(on Turbo engines) . Porsche even electron beam welded the cylinders to the heads to attempt to keep these engines sealed at higher boost levels on 962s. Our 4 stud architecture is just pretty weak in the scheme of things, and gets worse and worse when as the bore gets larger and larger.. There simple is no more meat and mass left on the sides of the heads. Then we get to welding those up on the sides.... On and on the mods. Ideally , & for another time, a multi layer steel head gasket is likely the best fix and you can witness how that changed all the power levels through boost sealing on all these crazy modern cars -40-50-60 +PSI boost 800 hp+ all day , with some reliability, crazy.

Kevin
GAS Motorsport

[Neil Harvey]

I like the fact that the internet is used on this site to educate and give different opinions and suggestion. These are always welcomed when they are based on experience.

I have never seen the 'leverage" issue before but maybe because we have not seen any evidence of this happening. Not saying it isn't happening. As long as the parting faces do not leak, looking for any other issues has never given cause.

One issue we do see lot of is the Head stud washer platforms often are deformed. Under compression, the hole in the Cyl head collapsing inwards and the platform is now not flat. This can lead to the head nut from loosening. We have a stepped insert that goes down inside the head bore to stop the head from moving. I am certainly going to look into any other defection that may be going on that we are not seeing.

A mention on our sealing system. Both the compression ring and the flat head gasket are under crush. Both have different amounts. The image I posted of the used engine apart was a "hotrodded" turbo engine that had many hours of use.

A mention was made about the 962C water race engine that had its liners EB welded to the heads. I remember these very well from my time rebuilding these at Andial. They were replaced almost very race at about $ 6000.00 ea. And an absolute nightmare to do the seat work.

When I started PD, we has several 962C customers and the very first mod we did was to remove the cylinders from the heads, and install individual liners. This was the actual "invention" of the sealing system we still use today on all air cooled 911 engines. Some slight differences in ring sizes etc. And it made the seat work a lot easier. The customers loved it as it saved thousands of $$'s, the Cylinder heads could be reconditioned and reused multiple times.

The same as the later GT3 and Turbo water engines.

There is many ways to solve a problem. What is really good is that there are many to choose from.