I really think I agree, Andy. I think Henry said he found the 17-4PH studs in a high powered turbo race engine (perhaps 962), I wonder whether the thermal expansion on that material is similar to or different from the 200ksi alloy steels, but I'm too lazy to look it up right now.

I had Henry put supertec studs in my engine aout a year ago. They have served me well so far...Why did I choose the Supertec studs? First the lifetime warranty. You cannot have any more confidence in your product than that. Second, I have observed that broken and pulled headstuds seem to be a prevailing problem based on posts here...broken with dilvar...pulled with others (That was the problem with my old 2.7). Henry's studs have a history of doing neither...even under extreme conditions. They did not cost that much more either. It seems to me that people on PP BBS overkill on so many parts..suspension, brakes, cupholders, etc, then try to save a buck on the most important part...their engine. I figure that it is one of those "while you're in there" things. I don't intend to be "in there" for at least 100k after a Supertec rebuild...so amortizing the difference over that many miles makes the better quality a cheap investment. And like most of you guys...I run my engine pretty hard. For my engine...overkill is good.

Yes, we see it all the time. Failure is measured in degrees as is performance. As for Delivar in 935s not in the one's I've seen. [see picture]
Porsche redesigned their heads studs at least 5 times in an attempt to improve stud performance. Porsche is a great design company but designers sometimes have cost constraints that impair their designs. When we designed our stud,we designed it with performance in mind, not cost. We looked at how other engine designers remedy these problems. All performance engines that I have worked with that had a steel head stud in an aluminum case or block used a coarse thread in the case and a fine thread at the nut end. (see Continental aircraft engines, high performance motorcycle engines, Ford, Chevy, Rolls Royce, BMW and the list goes on). And what's with the allen head nut ? A 12 point flange nut is the best hardware for this application.
Performance you say? What can a head stud do? Simply put, a head stud holds the heads in place. When you build a large number of engines that come apart with very low mileage ( race engines) you can see problems that quality engine builders want to remedy. Head movement is the problem and our studs reduce that problem to an exceptable level. Whether you make 200 hp or 800 hp our head studs hold the heads in place. This is not our experience with stock steel studs.

It might be ridiculous to assume that if it hasn't broken, it must work just fine.

As for thermal expansion, all the head studs ( Fcatory Porsche, ARP, Raceware and SUPERTEC) are made of differing materials so they all expand differently. The key might be to look at why Porsche chose Dilavar. It is my understanding that Dilavar was chosen in an attempt to stop the heads from leaking (seeping) during and after cool down. Leaking oil not compression. This was the reason for the missing fins on the 3.3 (78-89) Turbo cylinders. We prefer to build an engine that functions well during running and we'll let cool down take care of itself. The 993 stud is steel so apparently Porsche have taken the same direction.

Raceware, stock steel, updated Dilavar (all thread), old Dilavar, Factory 935, Supertec, 993 steel
http://forums.pelicanparts.com/uploa...1100620193.jpg

The 2nd one from the left looks like the Raceware I've used.
-Chris

The second stud is a stock steel stud that was cad plated.

They all look so frail and puny in comparison to the 935 and your head stud. Also yours and the 935 stud look eerily similar, in a good way! keep up the awesome work henry.

im with flintstone, surely overkill is better than a 20-30% saving on cost when it comes to key engine components?

Andy

Henry
Do you recommend retorqing your head studs at valve adj? If so, to what value? Any special instructions?

Hi Stoney
No retorquing but if you would like to check it the torque should be 30#.

Thanks Henry!

17-4PH is an excellent stainless "spring steel" with high yield strength (180KSI +). Its coefficient of thermal expansion is close to carbon steel. I've used it very successfully in the design of loadcells and as the host material/Mechanical amplifier for silicon strain-gage based bolt-on stress/strain gage designs. The high strength and temp match to carbon steel is ideal for these applications, high stresses and cycles, and as we can see for others as well.

Performance Developments, at Costa Mesa,(I think),they sell and use those studs,(Henry's), cheers,Antonio.

Henry, being Sunday today, I have been re-reading old threads about studs :D and I have just found two quotes that I find interesting. See below. So I'm wondering if your studs are manufactured in the same way? Can you confirm?

You'd be wrong. Neil does his own.;)

Ralph

I know, I only use Neil's stuff, they look similar thou, cheers, Ant.

The specs on our studs are as follows.
17-4ph HCR 38-42 4hrs @ Temp 1025
http://www.latitudemanufacturing.com/174PHPrint.html

The process is first to cut the round stock to length. Next we center less grind 3 times. Each end must be ground to the size specified by the tooling company for each thread roller. Then the center is ground to remove the transition (possible stress riser). Then they are heat treated to 1025* for the prescribed time (4hrs). At that point they a Rockwell tested to insure they are within specs (38-42).
Then the threads are rolled, each end receiving a separate thread pitch.
The threads are checked for depth and consistency.
The finished product is then polished to insure a quality surface. At that point they are inspected to ISO-9003.
We tried having a new company manufacture them to reduce cost and the result was a 300 piece sample run in the trash.
As you can see the process is lengthy and expensive. We build them because we wanted a better stud. If no one ever buys another one I will still make them for Supertec engines.

Ok....you got the attention of an amatuer steel geek here...lol. Do you know what thew alloying elements are and does it have similar properties to "high speed" steels as far as resistance to tempering goes? I ask because is supect that head studs might be close enough to some heat that could soften them up a bit over time if they werre made of standard springor carbon steel like 5160, 9260, 10xx series, etc. I use these to make knives and i can temper 5160 in my oven at around 350 degrees.

38-42 Rockwell is pretty soft compared to what I am used to. I shoot for 57-58 on my edges and probably high mid to high 40's on the spine of my knives....and they can be bent to the point where they don't spring back. Sounds like your studs are being annealed and normalized down pretty soft before HT. I would guess that you really don't have to worry that much about stress risers:D

To get closer look at the 935 stud, peek here http://forums.pelicanparts.com/showthread.php?s=&threadid=270137&highlight=name+t hat+stud