90 C2 - 964 rebuild

[JWPATE]

I will not even attempt to detail all the steps in the rebuild which is about to get underway. Kirk has already done that with his 964, and better by far than I could ever do. But as I come to things I am unsure about perhaps I can post a photo or two, in hopes someone else has been there and can point out the errors in my approach. Haven’t done a 911 in about 30 years, and never a 964.

Looking today at the head studs and nuts, I haven’t really come to a decision yet. I took the studs all out of the case because the 1-2-3 side had been gooped up with red RTV at some time past ?? Don’t know how anyone could think that oil would be leaking out there. Anyway, I just took them all out for cleaning and to reseal the threads in the case.

I left them all in a tray of paint remover overnight to get all the epoxy paint off, so I could inspect more closely for signs of corrosion. In the photos below you can see that the intake studs all came out clean but the exhaust studs clearly show where the greatest heat has baked that epoxy so hard that the paint remover had no effect at all. In the last photo I have bead blasted the remaining paint from the exhaust studs and it also took off that gold colored surface treatment. It is a very thin coating, and I don’t expect they would have done any electroplating on these studs. Was it a hot bath treatment?

I have given them a new coating of epoxy paint now, but am thinking of replacing the 12 exhaust studs with new ones (they are all Dilavar studs) since they have already seen 16 years and 58000 miles of heat cycles. Then I wonder…….why don’t I just switch them around and let the previously intake side studs now get the heat ……and see whether they will all go another 58,000.

[JWPATE]

Well today I finished the head studs. They have new epoxy paint now and also I bead blasted the nuts and plated them in yellow zinc.


That second photo though got me thinking about how different the heat is on the exhaust side studs. And that line of thinking lead to the question of just how much advantage is there in Dilavar studs. They expand at about the same rate as the aluminum, true; but they are never at the same temperature as the aluminum.......and never at anything like a uniform temperature from the hot side to the cold side. It would seem to me that the tension on the studs will clearly increase as the cylinder/head temps rise, even with Dilavar studs. Also the increasing tension will be different depending on where the stud is located. My simplistic notion that the Divalar studs would maintain nearly constant tension across the operating range is really foolish, and a result of accepting the hype without ever really thinking. The Dilavars may have improved the thread-pulling situation on the magnesium cases, but they are certainly not without their own reputation for breaking. In short, it now seems really a moot point to me, steel vs. Dilavar......and thinking that way, why take a chance on a broken stud? Reluctantly and slowly, while working on and thinking about those studs, I have decided that I have joined the steel stud camp on this issue. I have read that the company also reached that conclusion late in the air-cooled model run.
So, I shall not be actually using the studs in the photos. Since it is to be steel studs the only question is which are the best among those presently available. That question at least is easy for me.....after posting this message I shall order a set of the Supertec head studs from our host.
James

[88-diamondblue]

Best choice you could make. I put steel in my rebuild as the budget just didn't allow for Supertec studs. Enjoy the rebuild!

[herman maire]

Yeah I second that.... I would 100% at least buy all new 993 studs+nuts.
Its just not worth it to put that old Dilavar grabage back in there. You already wasted too much time cleaning those evil dilavar parts

993 stuff is pretty cheap also.

[JWPATE]

The pistons and cylinders will be this set. They are the later 964 design, with more seating surface at the head and provision for a sealing ring.
The heads, crank, rods, rockers and cams have been delivered to The People's Republic of California. They will soon be subjected to a close scrutiny under the watchful eye of Herr Henry Schmidt. Those parts which pass muster will then be reconditioned to the high, exacting standards of the Supertec team. I have done the best I knew how to do, for those parts.
Meanwhile, back at the desert, I am passing the time by attending to those needed repairs which can so easily be done in this partial state of disassembly.
The transmission has never had a thing done to it during the 16 years it has run like a thoroughbred. Well, other than fluid and oil changes, that is. While it is out I intend to replace all the seals where a rotating shaft leaves the case. Think it workes out at five seals and three or four o-rings. Plus a gasket, for that front section of the transmission must come off in order to change the intermediate shaft seals. Good thing I ordered early, for our host couldn't source those seals and Porsche is having to go back to the Fatherland for them. Not that many calls for tiptronic parts I suppose.
With the engine out this is surely the time to get at that engine bay with soap and water. My general attitude is that any part made from rubber needs renewal. If it has gone this long without failure, it should be retired with honors. The rear engine mounts have been replaced......but no honors there, as they were both fully collapsed. I have replaced all the oil hoses, both pressure, returns and vent hoses. BTW, those pressure hoses are expensive, because they contain large expensive fittings. In retrospect I could have just replaced rubber sections at a fraction of the costs. The hoses are 22mm ID and 30mm OD. Probably would be a pain to source the hose, but worth it and I have saved the fittings for next time. This is even more true for the oil cooler lines, with their long metal pipe runs.
I replaced the foam sound pad there on the firewall, and the rubber flaps that surround and seal the engine sheetmetal.
I replaced the rear shocks while they are so easy to get at, and will do the same for the front when the engine is back in.
There are three or four fuel hoses there at the firewall, which must be replaced while I can easily do so. Actually, they are just short rubber hose-ends of long metal lines running forward. Same story as the pressure oil lines. These particular hose sections appear to be unusual at 10 mm ID. I have some on order and will try not to forget them in the excitement of engine building. (Just went out and hung tags on them just to be sure).
Can you suggest anything I have missed here in the engine bay.

[JWPATE]

The oil cooler was sent out for cleaning and pressure testing.
PACIFIC OIL COOLER
Laverne, Calif.
909-593-8400
Fast turnaround and First Rate Service.


While it was apart for cleaning, I tested
the thermostat in a bath of hot oil. It opened
at 185 F. Seems about right to me.



Oil tank was also sent to Pacific Oil Cooler, again for
cleaning and pressure testing.



Correct thing here would have been to fit new
rubber hoses and reuse the fittings and brass pipes.



While fitting complete new hose assemblies, as I did, would
probably be appropriate and normal practice at a dealership;
here with the DIY advantage of free and unlimited labor, I view
it as a boneheaded and wasteful action, deserving of the
Pelican Dunce-of-the-Month Award. Shame on me!
James

[DW SD]

Wow-
You've got a nice, clean car there!
Looking good,

Doug

[rcwaldo]

Wow, such a clean car throughout!!! I look forward to follow this thread!!

[JWPATE]

The case through-bolts were just cleaned up and the threads
chased out. There appears to have been no plating or coating
used and so I have left them natural; and there doesn’t seem to
be any need to consider replacing them. Are there any issues
here that I am not aware of?

The washers look to be a nice improvement, with that spigot to
extend down a drilling in the case, giving the o-ring just the right
compression, with the shoulder to prevent them going too far.
Old news I suppose – but new to me.

Well yes there is one issue I found that we need to be aware of.

While these washers seem to be an improvement, they are not
without a potential for mismatching them if replacements are
needed.
An early run of 964 engines were built up using a similar washer
but with a shorter spigot (5.8mm vs. 6.3mm). The short washers
are long since out of stock In the event you have one of those
early engines and need a replacement washer, then you should
order the longer version in this photo and dress it down to match
your others.
Porsche Tech. Bulletin 9107 has the details, or you can just
remember to compare any replacement washers you need with
the remaining originals. Or, if your memory is anything like mine,
get out volume one of workshop manual now, go to page 13-25,
and make a note in the margin next to item 23: Two spigot
lengths – check any replacement.




The chain housings and covers were cleaned and also left
natural. One thing did surprise me when I attempted to back off
the cover nuts – those 19 shouldered studs around the housing
face all came out of the case instead. The manual refers to them
as collar pins and they are to be set into the housing with Loctite
270 and 5 ftlb. Yet the 6mm nyloc nuts all had a higher friction
grip…no exceptions. Does Loctite 270 not set up very well in
magnesium?? Any Loctite experts in the group?

[JasonAndreas]

Originally posted by JWPATE
One thing did surprise me when I attempted to back off
the cover nuts – those 19 shouldered studs around the housing
face all came out of the case instead... Yet the 6mm nyloc nuts all had a higher friction grip…

Porsche used all-metal locking nuts on the normally aspirated 964 so if you're finding Nylocks then someone else has been in there before? What did you use to clean the chain housings and their covers? They look really good!

[ischmitz]

Make sure you scrape the gasket surfaces with a razor blade or sand them. The magnesium corrodes over time and leaves a pitted surface behind. If you do not samd them true or scrape them chances are that they will be leaking after the re-assembly. Ideally - the scrapping should leave a shiny alluminum-colored surface behind. That allows the rubber gasket to do its job properly.

Cheers,
Ingo

[JWPATE]

Thanks fellows, great advice.
I send a closer look at one of the covers, for that last photo did
make them look darker than they really are. They actually look
more like aluminum now until they oxidize back to darker grey.
On closer inspection, yes the lock nuts were indeed all-metal,and
I have made a note to source some new ones.
The pitted surface you refer to is certainly present and can be
seen in this photo. I am thinking of taking the studs back out
and sanding the cases on a plate of glass to see whether they
can be brought to a more perfect surface.
Oh, the covers were soaked overnight with paint remover in the
gasket grooves, which did loosen all the stuck in rubber remains.
Then both the covers and the cases were blasted with small-grit
glass beads (oil inlet/outlet holes first covered w/duct tape.)
Finally everything washed with soapy water.

[JWPATE]

Decided to proceed with sanding the chain case sealing surfaces.
Also did the covers, but they take almost no time at all.

Order of battle here is dry, Norton 220 grit paper on ¾ inch plate
glass surface. Surprising to me how out of level the case
surfaces were. In fact, by the time they were sanded flat, most
of the surface pitting was gone.

Tomorrow I will move on to 400 grit wet-or-dry briefly, then chase
out the threads again and put the studs back.

Thanks again for suggesting it.

[ischmitz]

NICE job - it will make sure the chain housings won't leak. They are notorious to do that after rebuilds buts your look awesome now.

You also might want to really carefully smooth out the seating surface of the large O-ring to the cam housing. This is another spot where oil leaks are comon.

Cheers,
Ingo

[JWPATE]

A question:

Got back an order of parts from Porsche today including
the six bolts I ordered for the knock sensors. They are the
part number from the workshop manual........but the wrong
bolts. So the manual is wrong, or the numbers have changed.
Catch 22. Change every time - but bolts not available.

The manual specifies encapsulated bolts, to be renewed every
time. I presume the reason for encapsulated bolts rather than
the usual loctite 270 is because of the critical need that they
don't loosen, and given the location (one bolt in each head) the
loctite could break down in the heat (it's rated to 300 F, but
seems to give up sooner than that when I heat up studs for
removal).

The bolts that came were encapsulated but were 8x30 rather
than 6x30 as needed. Troy at EBS is checking around.
Do any of you 964 experts know the full story? Sure don't want
to end up with loose mounting bolts setting off false knock
signals and limiting power.

James

[kirkf]

Knock Sensor Bolts-
In the end I used loctite on my old bolts. I asked around and everyone else said they had done the same thing.
I think someone else tried to source the bolts through pelican and were told they were no longer available.

Nice rebuild so far!

I cant believe how clean and new everything on your car looks.
Everything looks like new. Cars in the desert sure don't age.


Kirk

[JWPATE]

This is Las Vegas Kirk...........we use smoke and mirrors.

[JWPATE]

CAMSHAFT HOUSING SERVICE
In the Redkneck tradition

Clean the baked-on grime with M.E.K. or with lacquer thinner.

Remove the studs and have a go at the sealing surfaces using
the same sandpaper-on-glass-plate approach as with the chain
cases. Slower going on the aluminum compared to the
magnesium. Goal is a truly flat surface without removing more
than needed. Check progress often and not a stroke more than
required!




Drill 4.8-5 mm hole into oil tube end plugs. Go in 8 mm or so
only – not completely through the plug. Use a bottom tap and
cut 6 mm threads. Fashion a jury-rig of your choosing to pull the
plugs from their bores. Now a soft rifle-bore style brush and
favorite cleaner (I used red-hot), with fresh water flush. Plug one
end with your finger and watch the oil line spray patterns from
the small drillings, as well as checking that the cam drillings are
free and have full flow. Scrub well and blow dry.


Press in new end plugs to just below surface, so no fouling with sealing gaskets later. Chase out all threads and replace studs w/loctite 271. Put in safe place until needed in rebuild.







There is one open issue regarding the cam-towers-to-head
fasteners.

Porsche Tech. Bulletin 9403 advises the replacement of the
familiar cam-tower studs/nuts with Allen bolts, and doing the
same at the intake manifolds. Because this change to Allen bolts
strikes me as crude and a step backwards, unless otherwise
persuaded I do NOT intend to implement the change. Can
anyone enlighten us on the issue? What was the motivation
behind tech bulletin 9403?

[JWPATE]

MICROENCAPSULATED BOLTS….REVISITED

OK Kirk, and anyone else with an interest, I believe we have
peeled away to the bottom on the knock-sensor bolts issue.

First, the encapsulated technology was/is new to me, but here I
think it is in a nutshell. Unlike loctite or other threadlockers
(which are anaerobic in their action), the microencapsulated bolts
are a two-part epoxy product, using tiny (.001 in.) capsules to
isolate one component and prevent catalytic action until the
fastener is tightened. Then the threads crush the capsules and
activate the epoxy, which then seals and locks the threads.

The confusion we have been faced with, regarding the knock-
sensor bolts, appears to be the result of a single typo in the
Porsche Workshop Manual. Go now to Volume One, page 15-19.
Under the “Installing” heading find (M 6 x 30) and correct it to
read (M 8 x 30).

The reference to “microencapsulated” and “always replace”
should correctly refer only to the single bolt which attaches the
sensor to the bridge. Those 6 x 30 bolts attaching the bridge to
the heads never were microencapsulated in the first instance.

James

[JasonAndreas]

Originally posted by JWPATE
The bolts that came were encapsulated but were 8x30 rather
than 6x30 as needed. Troy at EBS is checking around.
Do any of you ... know the full story?

The correct part number is #900-074-015-02 and it shows up in the November price list so they are still available.

Originally posted by JWPATE Porsche Tech. Bulletin 9403 advises the replacement of the
familiar cam-tower studs/nuts with Allen bolts, and doing the
same at the intake manifolds. Because this change to Allen bolts
strikes me as crude and a step backwards, unless otherwise
persuaded I do NOT intend to implement the change. Can
anyone enlighten us on the issue? What was the motivation
behind tech bulletin 9403?

Based on the date this changeover occurred (February 1993) and the decision to use caphead screws inplace of studs everywhere else on the 993 I'm guessing the reason was to reduce the number of steps in the manufacturing process and to have a reduction in the number of required parts? Instead of a stud and a nut all you need is one cap head bolt which involves one less operation during assembly saving time & money.