90 C2 - 964 rebuild

[JWPATE]

Thanks Jason,
And see the post just above your own. The confusion
was whether the three 6 x 30 bolts from knock sensor to heads
should be micro encapsulated. Answer is no - they never were.

I expect you are correct about the Allen bolts. That is what I
also suspected........and why I will stick with the studs/nuts, which
I consider to be a better fastening in this application.

[JWPATE]

Cleaning the engine case now and that work inevitably leads one
to the piston squirters. Here the sections of ¼ fuel hose are
blocking the through-bolt passage, and allowing pressure to be
directed on the squirters through the bearing oil feeds.

I have been at them long enough now that further cleaning isn’t
going to change the situation. They required a lot of air pressure
to open, especially at the start. Now they all send forth a nice full
spray with each tiny thimble-full of solvent, which can be filled
into the lines. I have done the exercise over and over……and
over again.

At this point I find that the squirters open and send a nice spray
at between 45 and 50 PSI, measured right there at the air blow-
gun nose. Below that pressure they just dribble. This is a
greater pressure than I expected, but this is my first time with
them. Anyone have a spec. for them? I haven’t found one. I
thought they were only going to protect idle oil pressure at, say
30 PSI or so, and am wondering whether I should change them
all???

[CBRacerX]

I believe the oil squirters are not supposed to open until they are around the level you noted. So don't worry

Good luck and enjoy the rebuild!

[JWPATE]

Thanks Chris,
That is certainly what I was hoping to hear. They must be
simple spring/ball valves.

[black993]

Outstanding work, thanks for sharing. It looks like you have done this a time or two before.
I appreciate you taking the time and effort to allow me to learn from your experience.
Art

[kirkf]

MICROENCAPSULATED BOLTS….REVISITED

Ahh thats what they meant.
I never removed mine from the knock sensor. So I guess I am safe on that one.

Kirk

[JWPATE]

CHECKING THE MAIN BEARING BORES

Assemble the case on the stand, including through bolts/nuts and
those 8 mm nuts surrounding the bearing bores at each end.
Nuts taken up but still slack.

Use the rubber mallet to persuade the case into as nearly perfect
alignment as possible. Take diagonal measurements and keep
adjusting with the mallet until differential is less than one
thousands of an inch.

Tighten the through bolts/nuts and 8 mm nuts to final torque
values. Check the case alignment didn’t change.

Break out the bore gauge, and discover it is too big for the job.
Switch to an internal micrometer supported by a good strong
magnet and check the bores. New spec. is 65.00 mm and wear
limit is only 0.019 mm (less than a thou. of an inch.). Converted
to inches, for my micrometer, the spec. is 2.559 inches and a
wear limit only out to 2.560.






Use the internal micrometer as a go/no-go gauge. Set first at
2.559 and insure it will fit every bearing bore. Then go to 2.260
and insure that it will not.

Don’t know that the exercise is really necessary, where there
were no shiny spots on the saddles or other evidence of bearing
movement. Without checking there is always doubt though, so
worth it for peace of mind.

[JWPATE]

ENGINE PARTS ARE BACK – RECONDITIONED

The crank remains standard, but has been mag-tested and
polished

The cam shafts were reground – Dougherty Racing Cams – to
standard 964 profile with lift set at 1.26 mm

Heads reconditioned and surfaced for the later style 964
cylinders – with sealing rings.

Rods reconditioned – new wrist bushings. Rockers were OK
except one – which was replaced – others reconditioned.

All machine work is beautifully executed and a joy to gaze at.
Thanks Henry!

SUPERTEC PERFORMANCE
FALLBROOK, CA
760 728 3062

[racing97]

While using the dial bore gage it is advisible to leave the nose beraing in place for porper alignment, unless you are shaving the case it is much more cost effective to align bore the Thrust through no. 7 the nose brg. is terribly expensive and not that important to the task at hand.


regards

[JWPATE]

Thanks for that tip. It would have certainly made alignment easier, and I will make a note to that effect in my manual for next time.

[JWPATE]

This is the starboard (4-5-6) side cam housing, after the same
treatment the port side got, with one twist. That threaded hole
at the upper right had a broken-off nut/stud (?) complete with
embedded, hardened-steel removal tool, also broken off flush.

Question for you experienced 946 experts: Can anyone
remember what that fastener was used for?? I expect it was a
hex bolt, and probably fastened a hose or wire harness strap. It
was already busted when I came along, so can only guess. The
location is above number six and that bracket, in place for
reference, is the support for P/S pump.

Tower went over to California for electrical discharge treatment;
excellent service at very reasonable price, and with lightning fast
turn-around. Highest recommendation for:

JERRY’S BROKEN TAP
SANTA ANA, CA
714 836 6824

[JasonAndreas]

On my non-powersteering RSA that nut holds the black plastic heat shield (PET calls it a duct) to the engine and nothing else. I have some closeup photos (if you need them) of that bolt on the other side (1-2-3) but nothing of the right side (4-5-6) bolt.

[JWPATE]

Thanks Jason,
That is probably the case on this engine also. I didn't notice
any hose or elect. wire clamp in the area that wasn't fastened.

BTW Jason, I notice that you call it a nut on the 4-5-6 side and
a bolt on the 1-2-3 side. Is that correct? Accepting that probably
it did nothing other than fasten that corner of the shroud, was
it a 6 mm hex bolt or was it a stud/nut combination?

[JWPATE]

HOPE SPRINGS ETERNAL……..

No effort is being made in this rebuild to increase power output
or to make the engine more able to sustain high rpm’s. The
simple goal is a sweet running engine WITHOUT oil leaks; clean
surfaces and no smell of burnt oil after a run.

The cam tower sealing surfaces have already been brought to as
flat, true and smooth condition as I am able to achieve. Now the
valve covers receive the same treatment. The two exhaust
covers are new, and are of an aluminum alloy as used on the
later 964 engines I am informed– though I cannot confirm from
the PET whether this is correct information. The hope is that they
will be less likely to distort/leak than the original magnesium
covers.

All outside surfaces, along with the air-guides have been powder
coated in an aluminum shade. Those plastic, wire clips were
moved over from the original covers. Do this change, and you will
find that the new aluminum covers already have the screw holes
in them, but they are not threaded. Those original screws are
stainless and can be reused, but I found it best to shorten them
by about 2 mm, as the new cover holes are not so deep. Also,
the threads on those screws are wider than anything in my
metric tap set; more like sheet metal threads. I found that a SAE
10-24 thread is nearly a perfect match. Set in with Loctite 243
(blue).

Don’t know anything else to try so now is time to hope, and hope
springs eternal!

[JasonAndreas]

Originally posted by JWPATE
I notice that you call it a nut on the 4-5-6 side and
a bolt on the 1-2-3 side. Is that correct?

Sorry about that, it was me being sloppy at 2am. The fastener is an M6 x 16 bolt and I believe stainless steel.

[JWPATE]

Thanks for the information Jason

[CBRacerX]

I just "finished" reconditioning my stock '90 covers and I envy your results. The paint/coating on the covers was very hard to remove, I did a lot of dental pick on the areas that my paint stripper/glass beading process did not clean. I chose to paint the outside in black ala the 993 covers, and left the insides raw magnesium. I spent _far_ too much time on this, and I am still not happy with the results!

[JWPATE]

Time to record the weights and decide which rod goes where. I
expected these rods to be right on, and they are. The bores are
as perfect as I can measure them and the weights vary only
about a gram.

This is how I plan to put them in. They are so close it doesn’t
matter much, but it is interesting to note that this is not how they
went in from new.


The crank measured near perfect too, as expected. The
measuring seems unnecessary really - worth the effort though,
for this part is fun, provided the time clock is not an issue. And it
provides calm assurance that all is well……….so far.


I just used number one and eight bearings here to check for run-
out. Too little for me to measure on the dial gauge, though I
could just detect the needle wiggle. Would love to start building
it up now, but we are going to Berlin in the morning for a Holiday
visit with family there. So the project is on hold for a while.

[kirkf]

Enjoy your holiday.
I'm looking forward to seeing the project continue when you get back.

Kirk

[JWPATE]

Back in Nevada again and time to get on with the project. The
crank is a natural place to start. I cleaned it as well as I am able,
including flushing out all the oil passages with brake cleaner and
compressed air.


Here the individual rod bolts are measured, to serve as a point of
reference when next the engine is apart. While I like to keep
things mostly stock and standard, I have deviated in this case,
and with a few other items. These are ARP, aftermarket rod bolts
in 9 mm, Part # 204-6005. The instructions do include a torque
value but the recommended installation is by controlled stretch of
the bolts to a value of 0.012 inch. A dial gauge is available for
stretch and I did use it, but that requires that the tightening be
done with a closed end wrench. The nuts are 12 point and nice,
BUT they are only 11 mm and we are up around 40 foot pounds
to reach the 12 thousands stretch. Therefore, I did find these
preliminary rod length measurements to be useful in the initial
setup. Several of the rod nuts were just much easier to tighten
with a socket, while checking often to bring them to the 0.012
stretch lengths.


Lay out what will be needed, and get started. These twelve
fasteners are arguably the most important ones in the engine. I
moved slowly and deliberately to try and get the right rod on the
right journal, the right way around, and the rods all at exactly
twelve thousands stretch.
But what is wrong with this picture? Not to worry, the APR bolts
were put into the caps correctly - not as seen here.


This was a fun day. I feel good about the completed crank/rods,
and I am still glad that I decided to use the ARP hardware.