A Photo Diary of a top-end rebuild. Or, The Tale of a one-armed rebuild.

[Gunter]

Originally Posted by ianc

The adjusting screw will absorb the decreased clearance as the valve stem moves out.

If the spring is less compressed as the stem moves out, then there will be less preload on the spring and less force required to open the valve?

ianc

True.
Advantage would be less load/wear on the lobes of the cams but,
If the preload is significantly less, this might result in "valve-float" at higher RPM range.

Still looking for clarification on the 12 shims mentioned in the rebuild cost?
New OEM shims? Why?
Different OEM shim thickness?

[Dixie]

If the spring is less compressed as the stem moves out, then there will be less preload on the spring and less force required to open the valve?

Less preload causes valves to bounce off their seats. Not a good thing.

[Gunter]

Originally Posted by Capt. Carrera

Less preload causes valves to bounce off their seats. Not a good thing.

Yes, but the question is:
What is different about the 12 shims you mentioned?
Are they just new OEM shims with the same thickness as the old ones?

What is the difference between the OLD shims and the NEW shims?

[Dixie]

Yes, but the question is:
What is different about the 12 shims you mentioned?
Are they just new OEM shims with the same thickness as the old ones?

What is the difference between the OLD shims and the NEW shims?

Springs have an "installed height". The free length of the spring is greater than the length when installed. It's a simple a way of setting the spring preload.

The shims come in varying thicknesses. So you may need to add a shim, or swap some shims. What you end up with depends on how much was cut fro the valve face, how much was cut from the valve seat, and what shims you had to start with.

A good shop will mix-and-match, and only charge you for one shim per valve. Another shop may charge you for two shims they added, and never mention the shim they removed, and used on someone else's head.

[Dixie]

Yesterday I got the other bank of heads installed. Today was dedicated to setting the cam timing.

"Easy as pie", my friend Kevin told me. Well, maybe it's easy on a '79 SC. But it's a PITA on a Carrera. You see, there no freakin' way to hold the cams still on a Carrera! You set things up, rotate the crank, loosen the cam bolt and the cam moves. And since the valve spring is pushing on it, the cam moves a lot. I tried all sorts of techniques. finally, I digressed to the following: Get the initial staring point established, guess where the cam needed to be. Rotate the crank 360°. Note where the dial indicator reading is. Set everything back to the initial starting point. Guess at how much the cam needed to move. Rotate the crank 360°. Read the dial indicator again. Repeat ad nauseum....

Eventually, I got both cams registering at .048". Well within the timing window of .043->.055, but not the perfect reading of .049 either. Finally, I decided to call it quits. I'll recheck things tomorrow. If everything looks good, it’s on to the next step. And if I have to time the cams again? I'm going to scream....

Here's what the engine looks like now.

[GH85Carrera]

I don't know ANYTHING about cam timing, but there must be a better way. I can't imagine some factory engine builder doing it that way. There must be a way to make it right every time. I have enjoyed your post. Hopefully it will be many years before I have to rebuild my engine.

[Gunter]

For the timing, only #1 and #4 intake valves are set at 0.004", the rest is left completely lose to make turning easier, I think.

If I remember correctly, the cams on an SC are the same as a Carrera; they are interchangeable.

With the right tools, it went very smooth; no frustration.

Why would the Porsche tool P9191 (in the picture) not work on a 3.2 liter?

[efhughes3]

Well, my vast experience of one build completed last December will allow me to weigh in with the good Captain on his cam timing technique. I did the same thing. It was frustrating at first, fighting the cam movement. You do get pretty adept at the guessing, putting some "preload" on them to compensate for their movement, but it still takes a few goes to get them right.

After the fact, I've heard a couple of different variations that may make it easier:
1. Install all of the rockers, which would then collectively "grab" the cams, keeping them stationary. Sounds reasonable, I guess.

2. Use a longer bolt on the front of the cams that will bottom out in the hole. This would then allow you to hold the cams with a wrench, but you'd have to be pretty steady as we're tallking accuracy here on the dial gauge.

But, there is nothing wrong with what Capt. Carrera or I did, IMHumbleO.

[ianc]

Why would the Porsche tool P9191 (in the picture) not work on a 3.2 liter?

The pictured tool will work on 3.2's, but will not work on earlier SC's. Midway through the SC run, they changed from a cam nut to a cam bolt. Not sure exactly when, but my 80 had a nut, for which you need a special crowfoot socket and cam holding tool.

ianc

[Dixie]

Played with the cams some more today. I got them dead on. I finished up the day by installing the timing covers and oil lines.

[mca]

Rob,

Looking good! Really coming together.

Question: Did you do anything to refresh your wiring harness?

When I was manipulating some wires for labeling purposes the outter casing cracked in several locations. Not the casing of the wires themselves, but the casing that contians several bundled wires. Just wondering if you had any similar issues.

[Dixie]

Question: Did you do anything to refresh your wiring harness?

I did nothing to the wiring. It looks great. That is, unless you count the wires on the reference sensors. Those disintegrated upon touch. Oh, and I have to re-solder the connectors that plug into the backup switch.

[wilke3169]

Hi Robert, Glad to see your timing is now set. I do remember setting mine several times and resetting and swearing it had to be wrong etc etc. When i was done I decided it was right the first time. Actually the difference in the SC and Carrera may make a difference.
I noticed in the one picture that you had the manual tensioner laying up on the heads. Was this just laying there or did you use it for something else?

[Dixie]

I noticed in the one picture that you had the manual tensioner laying up on the heads. Was this just laying there or did you use it for something else?

The manual tensioner is sitting up there post-usage. Let me add, I'm not convinced it provided any benefit over the hydraulic tensioners providing static tension against the chains.

The issue with Carrera cams is more than twofold.

• The cams move when you pull the gear pin.
• When you move the crank, the unpinned cams move as well. And not necessarily a correlating amount.
• There is no way to hold the cam in place once they’re unpinned.
• There is no way to rotate the cams counter clockwise using the bolt. The bolt simply unscrews.
• Rotating the cam clockwise results in problems getting the bolt to disengage.

Trying not to get pissed-off appears to be the key….

[Gunter]

Originally Posted by ianc

The pictured tool will work on 3.2's, but will not work on earlier SC's. Midway through the SC run, they changed from a cam nut to a cam bolt. Not sure exactly when, but my 80 had a nut, for which you need a special crowfoot socket and cam holding tool.
ianc

Yes, I know, the '81-'83 SC has the center bolt and these cams are the same as Carrera cams; they are interchangeable.
If I remember correctly, on pin hole makes a difference of about 0.1 mm on the overlap.
I only set #1 and #4 valve clearance, the rest is lose.
After the initial installation of the 930-number on the cam pointing up, I rotated to see how close I was with the timing.

I calculated how much I was off, then rotated the engine a little to get the spring tension off the lobe and then opened the center bolt so I could get move the set-up to the right hole in the right direction.

Then re-check a few times and do the necessary correction repeating the above steps.
Found it very interesting and not frustrating as long as you take your time and think it out.

[tcesar888]

Subscribed!

[Dixie]

The project is at that point where progress is really visible. Got the valves adjusted, and the covers installed. Also got the heat exchangers on, and the intake in place. I do hope I got the oil line from the case tightened enough so it doesn't leak. I tightened it as much as I dare. If it does leak, I’ll have to drop the exhaust again.

Also, I broke a socket and bent a bunch of bolts trying to get the crank pulley off. (I'm using the bolts and a wrench as a flywheel stop.) A new 17mm 1/2" drive socket and some grade 10.9 bolts did the trick. Now I have replaced ever seal and gasket that you can get to without splitting the case.

Tomorrow I plan on getting the intake torqued down, the fan installed, and getting the transmission cleaned up some.

[wilke3169]

Very nice Robert. I am sure you are beginning to get excited about putting it back in. I can hear the track screaming your name...

[Dixie]

I can hear the track screaming your name...

Funny thing… The Bride® has spent more time at the track this year than I have. I think it's startin' to scream her name....

Back to the engine. I had an epiphany this evening. I need to get the engine off the stand, and then install the intake. Otherwise, the chain will interfere with too many things. Good thing I didn’t torque everything down. The rental shop is closed on Sunday, so tomorrow is limited to cleaning the trans and more engine tin....

[ischmitz]

Ask a couple of teens in the neigborhood to give you a helping hand. That's how I usually get my 3.6 on and off the stand. With three people it is kinda tough. Four and it is pretty easy. Leave the engine mount on and slide it out of the stand. Cheers,

Ingo