2.7 Head Stud

[GeorgeRud]

I just found that two of the head studs on cylinder 2 won't hold torque, and a leak down shows leakage between the cylinder head and barrel on that cylinder. The engine is a 2.7 that has been previously rebuilt with Timeserts and Dilivar studs back in the late 80s. Compression is good and consistent on all cylinders after they've been torqued, but they're loose the next morning. At this point, don't know if it's the inserts pulling out or can the studs stretch (as I thought I had read somewhere)?

Can case savers be used to replace the Timeserts if needed or is the case a boat anchor at this point? Any suggestions would be appreciated.

[KTL]

Head studs don't stretch. They just snap. Especially the dilivar type.

Since your studs are exposed along the cylinders, you could mark the suspect studs to confirm they're pulling. Put a paint mark across the stud and extend that mark onto the cylinder. Tighten it down and come back later to see how the mark has moved, if at all.

Are you sure the current inserts were Time Serts? They are pretty reliable since they are installed in an oversized bore and bite into more area within the case. But if they were helicoils, then I would think you're in better shape to re-do the case threads.

[chris_seven]

Kevin,

Do you think they are backing out with vibration when the engine runs? If they are backing out is it because the Loctite joint has failed?

If the Time Serts are pulling out of the case then it will just be down to axial force caused by expansion or by peak combustion forces as this is the only way that the load will increase.

At ambient temperature neither the case or the stud is likely to exhibit any stress relaxation due to a steady state load.

[Steve@Rennsport]

Case Savers are really more durable than Timecerts or helicoils in these applications and I'd guess your Timecerts may have started pulling.

I'd be looking for a better case thats seen less heat.

Hopefully, your 2.7 has a front oil cooler,.........

[KTL]

I wasn't thinking vibration loosening. Just thinking load applied to root was slowly pulling the stud out. Certainly agree that the running engine via thermal expansion and/or combustion force will apply the most load to move the stud.

[GeorgeRud]

The Timeserts were installed at the last rebuild, and were considered the way to go back them. We did all the tricks that Bruce Anderson recommended in his book. Wayne's book seems to indicate that you can put Casesavers in even after having the Timeserts installed, and that does seem to be the current recommendation.

The engine has always had a front mounted cooler and has never been run over 212*F, but I think age has taken it's toll.

[iceracer83]

I had the same issue in 1993, fresh rebuild on 2.7 mag case with Timeserts. But, it leaked between a barrel and head. A couple of the studs wouldn't hold torque.

Aluminum 2.0 case replaced the old mag case and the problem was solved.

The Aluminum case is noticeably heavier than the magnesium. But the aluminum case eliminated the leaks.

Jay

[GeorgeRud]

An aluminum case would be a great idea! Are they available through any sources? I'd imagine that they would be quite $$$$$$ if available.

I'm weighing my options at this point as I'd hate to spend $10,000 on a rebuild to have the case material fail once again. Has anyone had any failures with the case savers?

Also, other than Raceware studs to replace the old Dilivar ones, are the old steel head studs appropriate for 2.7 RS P&Cs?

[KTL]

There always an aluminum case out there somewhere. They're a bit rare but certainly not unobtainium rare. Put a WTB ad on the classifieds and you'd be surprised how many might appear?

For the cost of Raceware you can also consider, ARP, 993TT all-thread dilivar or Supertec's fantastic studs. My limited experience has seen steel studs run on some large bore engines with no ill effects. Most notable one has been a 3.3L N/A (3.0L case & crank with 100mm bore-in Nickies cyls + JE 10.5 pistons) that puts out ~250 rwhp. 250 is said to be around the max for them. Keep in mind that the 993 3.6 came from the factory with all steel studs. So if you go with steel, get the 993 studs to get the ones Porsche spec'd for the fatty engines.