Head studs, etc.
 

I am replacing all my dilivar head studs with steel in my 1976 911s since one stud recently broke and I don't want to take a chance on breaking another. There are a few things I am unsure about however:
1. What is the benefit of putting thread-lock on the head studs? The case has been time-serted. I sure was glad I had previously used anti-seize rather than thread-lock when I was removing the broken dilivar stud.
2. Is it worth removing all the cylinders to put in new cylinder to case seals (brass shims)? Is so, can this reasonably be done without removing the pistons?
3. I am adding a front fender mounted oil cooler and I am thinking about back-dating the exhaust to a pre-1974 system to help the engine run cooler during the hot Texas summer. Does the back-dated exhaust really help much with cooling or is this primarily a horse power/torque improvement?

Thanks,
Tim Fogelsong

I guess you don't need to use thread-lock but most of us do so that when we remove the head nuts at a later time the stud doesn't back out of the case. You might also have the stud back out on it's own though this seems unlikely.

I don't think you need to put new shims under the cylinders unless you see a reason to. If they aren't leaking or bulging out then I'd leave them alone. Yes you can do it without pulling the pistons out of the cylinder. Just expose the wrist pin and keep the rest of the piston inside the cylinder.

If you have the O.E. thermal reactors then backdating will help with heat issuses. If you got rid of that and just have an SC like set-up then you won't see an improvement in the heat department.

-Andy

Thanks Andy.

Have you considered 993 Dilivar studs for replacement? They are made of new improved Dilivar. Less chance of pulling a timesert out of the magnesium.

Also, thread lock probably help keeps humidity out of the threads and will let go with the proper amount of heat applied when removing.

Loctite says that the thread locker makes the attachment of the fastener stronger, I think.

I would not run plain steel in a magnesium case without case savers.

The new Dilavars come with the loctite on them - that could be the answer to all of your questions. I use the Loctite primer, too.

Tim,
When replacing a stud it is important to use identical studs in all case holes on each side of the engine respectively. Since the thermal growth characteristic is unique to the material they are made of, you can introduce a lot of additional mechanical stress when the engine gets hot. Over time the asymetric load will result in fatigue.
Putting studs in a case with anti-sieze is not a good idea. With a non-permanent threadlocker (like 242, that does not require heat for removal) you stand a much better chance of the stud not loosening during shock cooling (like a long mountain descent under engine braking) when the finned cylinders contract faster than other engine parts. If the stud loosens and starts to work, it is hell on the case. The threadlocker will be even more effective at excluding corrosion causing contaminants.
Most people don't know that KEENSERTS come in passivated stainless steel (with nearly identical properties to the carbon steel ones most shops install). You will not find an aerospace mfgr. that permits carbon steel inserts in magnesium or aluminum because of the potential for corrosion.
The high ultimate/fatigue strength (and high cost ) aftermarket studs can eliminate this broken stud problem completely. We have done a lot of work on making a product that works and is affordable. We have a lifetime guarantee they will not break (unless you modify them). We offer only complete kits with special nuts and washers for a lot less than Raceware sells their studs (only). Check with Scott Shores @ Pelican or call me if you want details 561-575-3157

Bill Ryan
Casper Labs, Inc.

Thanks guys for the advise. I guess I will use locktite and hope I don't break another stud. I have already purchased steel studs from Pelican based on their website recommendation.

Best regards,
Tim