90 C2 - 964 rebuild

[JasonAndreas]

Just to warn people in the future, where did you buy those valve covers?

[kirkf]

I used the imagine auto valve covers for my rebuild.
They seemed to work well. They are made from billet aluminum, very heavy compared to the stock covers.

For a 964 they dont have spots to mount the plug wire retainers.

Kirk

[JWPATE]

Thanks Kirk,
I had forgotten that you used billet aluminum on your engine. You
have a few miles on now so if they are not leaking that is nice
information to know.
For myself, I really so like the wire clips of the original style, and
they too were no-leak covers when new. It would seem that if they are
flat, as I have attempted to do with these, then the originals should also
be leak free. The design, with the compressed rubber gaskets should
last for many miles without leaks. Could it be that the black rubber
gaskets we are now getting are inferior? If I cannot resolve the leaks
on this set I probably will spring for a new OEM pair.

[kirkf]

I think the leaking is due to them warping when they are torqued. Hence the 89/90 magnesium covers leaked worse than the 91-94 aluminum covers.
The IA replacement covers are heavy, thick billet aluminum which can't warp.

I am going to be dropping my motor again next week to begin installing a supercharger. So I will have a good chance to see what I did right/wrong on my rebuild.

I intend on tapping some holes in the IA covers to accept some plug wire clips at that time.

As far as I know I have had no leaking from anywhere on my motor. However I still havent managed to stop the leaking at the thermostat housing. I went in and tried to fix it once, and I have never been back to try again.

Kirk

[CBRacerX]

Supercharger, eh? That will be fun to follow along!

[JWPATE]

Thanks Kirk,
I have been watching my own the past two days. Warming
up the engine (without driving so as to better isolate the leak
source – no wind factor), and then watching closely for leaks.
There is still one, a drop or two exactly in the center of the left
side cam tower bottom. It didn’t matter that I changed the
covers side to side, and it doesn’t look to be coming from the
valve covers anyway, but from the other side. I can only imagine
that it must be either a leaking rocker shaft or a leak at the
head/tower joint.
When the covers were off I checked the shafts carefully for leaks
and saw none.
So it is looking like an engine pull and resealing that joint. The
leak is so slight that it is very difficult to locate the exact source,
but I cannot think of anything else.

[JWPATE]

Further to the persistent oil leak I have watched since the
rebuild, as evidenced by a drop or two always present at the
bottom center of the 1-2-3 cam tower. As I previously stated, I
was hopeful that one of the rocker shafts was leaking, but alas
all were dry at the 2000 mile service. I could see that it wasn’t
the return tubes. They too were dry. That left only the sealing
surface between number two cylinder head and the cam
housing. Ugh!

So, last week it was R/R the engine, tear it down enough to take
off the left cam tower and reseal. Not necessary to take off the
heat exchanger or tamper with the intake stacks. The chain
housing likewise can remain in place. Have to break down the
chain sprocket of course and take out the cam. Later, you also
have to recheck the sprocket shims (they were still right) and
reset the valve timing. I was able to positively locate the source
of my leak. At the lowest point in the cam tower sealing surface
(it was #2 cylinder, as expected) is a dowel locating pin rather
than a stud, and I could see that the Three Bond sealant had
gone on too thin in that spot; it having skinned over, without
first sealing to the head surface.

The engine is back in now with considerable run time on it ……and
no leaks. Anywhere! The stock valve covers likewise are dry. So
this completes the engine rebuild sequence. Couldn’t be more
pleased with the final outcome.

Thanks to all for the many helpful suggestions along the way.

[CBRacerX]

Well done! I envy your dry garage floor. For now, I am just dealing my oil leaks - looking to the wintertime for an R&R to fix them.

Cheers,

[kirkf]

Congrats on the dry motor!

I had hoped to pull my motor out this week, but it took longer to finish drywalling/priming/painting the garage than I expected. So it looks like I will be pulling the motor in the 3rd week of July instead. (I have to go out of town for work for two weeks)

Oh well. The supercharger is sitting on my bench. I'll get it in eventually!

Kirk

[iangray100]

Its interesting that James had this leak ...so I have been checking my rebuilt engine now with over 2800miles on it, and its still 100% dry.

Must have had some "engineering" bad luck.

Ian ...fingers crossed