Head Studs - to remove or not?

[dgagne]

Hi,
I am currently in the process of tearing down my 69 911T engine. Today got the pistons and cylinders off and good news, they are in great shape! So far everything I have taken off appears to be in "good" shape, although I have not measured anything yet.

So in reading the book (p. 35) it claims the head studs may not need to be removed. The engine does not appear to have been split before (175,000 kms) but it has had the top end removed as I can see from the nicks in the bolts and that sort of thing.

There were no loose barrel nuts, they all came off fine. I cannot see any time serts in the case. Should I remove them or not. With an early magnesium case, should I bother if everything looks ok?

Thanks,
Derek

[john walker's workshop]

i would leave them.

[snowman]

I would remove them and time sert everything. Mag cases are very weak. The chance you take is as follows:

1. It works and everything is ok, for now, but after a few thousand miles the heads loosten up and will not tighten.

2. More likely, during assembly, a head bolt or other bolt suddenly keeps turning, stripped case. Some places can be fixed, but some require case to be split again.

For a hundred bucks or so you can purchase insurance against this ever happening to you, or you can save this hundred bucks to pay a couple of thou to fix it later, or more likely sooner.

My 2 cents worth. NEver put a mag case back togather without all timecerts, everywhere.

PS John W.

The most fun I had with my DKW (a 59, 4 spd on colum, 3 cyl, 2 cycle, ball bearing crank and rods, 3 coil crank fired ignition) was the 14 sticks of dynamite I put in it to see what would happen after I lit the fuse.

[Jim Sims]

I do believe the '69T had cast iron cylinders and produced 110 DIN horsepower; this combination (better matched thermal expansion between the studs and the components in their grip and less heat produced) did not have the stud pulling problem. I agree with JW that the OEM steel studs are fine if not corroded or bent. Cheers, Jim

[dgagne]

They are not rusted or bent at all, the nuts came off easily and the cylinders slid right off. Yes the cylinders are cast iron. The studs in the case at the moment are steel, hard to tell if they are OEM? Are there any marking to look for?
Looks like there will be some differences of opinion on this topic. I look forward to hearing what others have to say.
Thanks,
Derek

[Wayne 962]

If you are keeping the engine stock, then the best bet would probably to keep them in there. As Jim mentioned, these engines were not known as the highest performance engines of the Porsche line, and thus, did not stress the case as much. In general, the 2.0T engines just run and run and run, forever. They are one of the most reliable of the Porsche engines, probably due to the lower HP numbers.

That said, make sure you inspect your intermediate shaft bearing mounts in the case very carefully. This is the weak area for 1969 engines.

-Wayne

[Wayne 962]

Originally posted by snowman
I would remove them and time sert everything.

No, not time-certs, case-savers. Time-serts can pull out too (see photo of my engine case in the Rebuild Book).

-Wayne

[jim72911t]

Tough call. I'm almost done rebuilding a 2.4T with 2.2E P/C's and cams, and I opted to pay the money and have the case savers installed. Like yours, my case, crank, and rods looked very good after 130K miles, but since I'm going to be upping the HP a bit, I decided to upgrade.

Good Luck,
Jim

[snowman]

My limited experience with mag cases is that the failure occures during assembly. As mentioned in another famous book on Porsche engines there are a couple of places where you should fix the threads if needed or not, they are the places that would require the case being split it the screw strips during assembly. e.g the one next to the intermediate shaft.

OK I can see a helicoil strip out, but whats the difference between case savers and time certs? I thought they are the same.