Thinking of building your motor? New EVOMS Head Studs...

[Evolution MotorSports]

Originally Posted by m42racer If I came across arrogant it was not my intention. If you took it this way, then all I can say is sorry. I have absolutely nothing against the EVOMS Head stud. They look like they are made by A1 and this company make some great fasteners. My beef is and has always been how the ARP stud has taken it in the shorts when the problem is and has never been with the stud. We have used ARP studs for many years. If the average shop assembles a Porsche engine with ARP studs and uses the torque procedures that are recommended by ARP, there can be problems. Additionally, there are other issues that you mentioned when comparing the thread strength of the case vs. the stud strength. There are other procedures that have to be performed to increase the case strength that they make no mention of in their assembly instructions. So, this goes back to experience, understanding these engines, and recognizing the weakest link and improving upon it. The ARP is a decent stud but not perfect by any stretch of the imagination. The fact that their installation procedure is not even close makes them a liability for the average engine builder doing a few of these engines a year.

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[Evolution MotorSports]

Originally Posted by cjv

All in all, I believe that we are on the same page with a lot of the different opinions that were stated. I also believe that there are many ways to fix the same problem. Here are a few examples of problems – problems solved:

Example 1: Porsche race engines that made tremendous power lived under tremendous boost. Solution: Weld the heads to prevent lifting.

Example 2: Big powered air cooled 993 turbo engines. Solution: Nirosist ring (flame ring) the heads and cylinders to help prevent the side of the head blowing out when the heads lift.

Example 3: 996TT engine making tremendous power with stock head gaskets and head studs. Solution: increase head sealing pressures and combustion containment with additional copper or steel o-rings in the head

Example 4: 996TT engine making well over 1100 HP and 30 PSI of boost. Solution: 12mm head studs with more clamping pressure and a stronger head gasket without additional copper or steel o-rings in the head

Or you could do this . Thank you Chad. I knew I could count on you to combine a majority of these technologies Nirosist ringing has been around since the 70's on the boosted Porsche race engines. Since their were no head gaskets, the air cooled heads had a weak spot around the combustion chambers. If the heads lifted, the cumbustion energy could blow out the sides of the heads if they did not have this "flame ring" installed. Typically they were a 1.5mm thick stainless steel ring that were ~ 3mm tall. There was a receiving groove cut into the heads around each combustion chamber that was ~ 1.5mm wide by 1.5mm deep. This same ~ 1.5mm wide by 1.5mm deep groove was also cut into the top of each cylinder. This created a wall around the each combustion chamber that allowed some head movement without causing leakage.

As Chad has shown, a version of this can be accomplished on a water cooled 996TT engine and can be very affective to contain cylinder pressures. There are many different methods of head sealing that can all have the same end result. There are also methods of increasing clamp force on the heads to create a better seal. This can be done by dispersing the clamp force across a wider area around each stud as well as increasing the strength of the case. There also comes a point that the force of the head clamping can have an adverse affect on the entire case and start to distort the main journals. Lets face it, if the block were steel and built like a supra, alot of these problems would not be an issue.

[PALETTE]

Originally Posted by Evolution MotorSports

Or you could do this . Thank you Chad. I knew I could count on you to combine a majority of these technologies Nirosist ringing has been around since the 70's on the boosted Porsche race engines. Since their were no head gaskets, the air cooled heads had a weak spot around the combustion chambers. If the heads lifted, the cumbustion energy could blow out the sides of the heads if they did not have this "flame ring" installed. Typically they were a 1.5mm thick stainless steel ring that were ~ 3mm tall. There was a receiving groove cut into the heads around each combustion chamber that was ~ 1.5mm wide by 1.5mm deep. This same ~ 1.5mm wide by 1.5mm deep groove was also cut into the top of each cylinder. This created a wall around the each combustion chamber that allowed some head movement without causing leakage.

.

Question on the Receiver groove.
When you have Cut the head for the O ring i assume that the head has been squared first, Are you running a Ceramic seal through the cooling system to ensure that headstuds and o rings are not leaking? I have seen the head studs leak through the threads and through the water jackets, Not 100% sure if the Porsche 996 block has the water passage going underneath the studs.
I just want to ask so no one on the board says "well no one told me" That's why we have ENGINE BUILDERS!

[BBI Betim]

Originally Posted by Evolution MotorSports

Or you could do this . Thank you Chad. I knew I could count on you to combine a majority of these technologies Nirosist ringing has been around since the 70's on the boosted Porsche race engines. Since their were no head gaskets, the air cooled heads had a weak spot around the combustion chambers. If the heads lifted, the cumbustion energy could blow out the sides of the heads if they did not have this "flame ring" installed. Typically they were a 1.5mm thick stainless steel ring that were ~ 3mm tall. There was a receiving groove cut into the heads around each combustion chamber that was ~ 1.5mm wide by 1.5mm deep. This same ~ 1.5mm wide by 1.5mm deep groove was also cut into the top of each cylinder. This created a wall around the each combustion chamber that allowed some head movement without causing leakage.

As Chad has shown, a version of this can be accomplished on a water cooled 996TT engine and can be very affective to contain cylinder pressures. There are many different methods of head sealing that can all have the same end result. There are also methods of increasing clamp force on the heads to create a better seal. This can be done by dispersing the clamp force across a wider area around each stud as well as increasing the strength of the case. There also comes a point that the force of the head clamping can have an adverse affect on the entire case and start to distort the main journals. Lets face it, if the block were steel and built like a supra, alot of these problems would not be an issue.

Great post +1, For readers who are not behind the wrenches(and the ones behind the wrenches), this is an extremely informative read. Good stuff.

[adam699]

Well, not sure how many studs per cylinder Porsches have, I'd say it's 4 looking at CJV's pictures, however I remember that Ford engines had the same problem when used in boosted applications and GM was far superior since it was using 5 fasteners per cylinder. I'm no expert on porsche engines and am yet to take one apart, althou someday I'm sure I will.

I believe that the problem might not be with just the fasteners itself, but how loads are distributed on the surface. Also, let's keep in mind that temperatures also make the block and the heads expand and contract. The oil sweat you see around the heads, probably doesn't happen when the engine is warmed up and running but rather when cold.

O- ringing has been around for years and is nothing new, but keep in mind that headgaskets usually don't blow unless there is detonation in the cylinders.

The way I see it the way the engine was made from the factory the HG is a safetynet. I'd reather pop a head gasket than bend a rod, crack a block, piston or the head.

[cjv]

Originally Posted by Evolution MotorSports

Or you could do this . Thank you Chad. I knew I could count on you to combine a majority of these technologies Nirosist ringing has been around since the 70's on the boosted Porsche race engines. Since their were no head gaskets, the air cooled heads had a weak spot around the combustion chambers. If the heads lifted, the cumbustion energy could blow out the sides of the heads if they did not have this "flame ring" installed. Typically they were a 1.5mm thick stainless steel ring that were ~ 3mm tall. There was a receiving groove cut into the heads around each combustion chamber that was ~ 1.5mm wide by 1.5mm deep. This same ~ 1.5mm wide by 1.5mm deep groove was also cut into the top of each cylinder. This created a wall around the each combustion chamber that allowed some head movement without causing leakage.

As Chad has shown, a version of this can be accomplished on a water cooled 996TT engine and can be very affective to contain cylinder pressures. There are many different methods of head sealing that can all have the same end result. There are also methods of increasing clamp force on the heads to create a better seal. This can be done by dispersing the clamp force across a wider area around each stud as well as increasing the strength of the case. There also comes a point that the force of the head clamping can have an adverse affect on the entire case and start to distort the main journals. Lets face it, if the block were steel and built like a supra, alot of these problems would not be an issue.

I actually do not believe the material is nirosist. I can't remember exactly what it is.

Our heads and case is set up for 12 mm studs that have all the tricks re taper, thread, cut washers etc. Certain water passages to two cylinders have been re worked to provide additional cooling. You can see the combustion chambers and exhaust ports have been ceramic coated. The head temperatures in previous engine dyno runs were running about 800 degrees cooler.

Don't forget the pistons will also incorporate extra cooling a la oil chambers under the domes. The liners also have hugh 965 type liner squirters that provide more cooling to the liners. The GT1 oil oil pump is three index and one index pulls the oil right off each head.

Now enough of being off topic before Joe gives me a another reprimand.

Again, a big thank you to EVO for advancing the state of the art for the 996/996tt with their new product.