SC wrist pin noise - rebuild now?

[poorshe911]

hello,
I have an awesome condition '83 SC with about 84K and even though it has been extremely well maintained, I have a wrist pin noise in #4 cylinder.
The noise has been evident for the last 2 years or about 1000 miles and is only heard at around 3K when you then step on it.
My plans are to do a rebuild over the winter but wondered what you all think of putting it off for another driving season of 500 miles or so.
Will the pin damage the rod or cause the piston to damage the cylinder?

Also, if I do the rebuild, is it worth it to regrind the cams to 964 profile?
I have SSI's, euro fuel dist and a recurved dist.

Thanks for any replies.

Michael - Webster, NY
'83 SC blk/blk

[boyt911sc]

Michael,

How did you come to the conclusion that the noise is caused by the wrist pin #4? Have you opened the engine before that showed a loose wrist pin? Just curious how to detect a bad wrist pin. Thanks.

Tony

[Bob Kontak]

Originally Posted by boyt911sc

How did you come to the conclusion that the noise is caused by the wrist pin #4?

+1 That is some serious decifering - how did you do that?

You cannot grind an SC cam to 964 dimensions. The 964 cam has a little more lift and a little more duration. That means welding metal onto the lobes then grinding.

[poorshe911]

Thanks for your replies.
My mechanic localized the noise (metallic sounding) to cylinder # 4 by using a stethoscope. When #4 spark plug wire was removed, the noise went away. A leak-down test showed the engine had no issues. leakage was about 5%.

Do you know of any other tests to do?
I'd love to prove it isn't the wrist pin.

[Bob Kontak]

Crap - That sounds reasonable. Pull the spark plug wire and then there is no bang to slap the piston onto the pin.

No additional driving season allowed. Get on it and fix it this winter. I am only five hours away in Ohio and Tony (boyt911SC) is about the same in the other direction. Don't chance it.

[efhughes3]

I'd not drive it with that condition, if correct. Noise means parts are not working well together, and destruction/damage is in process now.

[Bob Kontak]

Originally Posted by efhughes3

destruction/damage is in process now.

+1

[Joe Bob]

De pin has been pulled, yer just waitin' on de BOOM !!!!!

[Bob Kontak]

I tol' you. Shut 'er down.

[db_cooper]

Never seen a bad wrist pin in a 911. Not saying it could not be..just..it would be unusual.

The test used would also indicate a leaking head gasket seal too..a more likely source of the noise.

In any case..time to do an engine pull..or just try and retorque the head nuts.

[prebordao]

Originally Posted by db_cooper

In any case..time to do an engine pull..or just try and retorque the head nuts.

A few weeks ago I noticed some oil coming between the barrel and head in cyl#2 (just like in picture).
Removed the valve cover and I was able to torque the nuts a little more...
Question: Could it be the nuts unwinding a little over time, or the threads are beginning to pull ??

[whalebird]

wrist pins are not easy to diagnose with 100% confidence. "typically" wrist pins are noticable when cold and go away with heat, but not always. Is it the pin/rod knocking, or pin/piston knocking? Also, a damaged piston could be "slapping" and sound/behave much like a wrist pin. I've heard this with JE pistons before.
Bottom line is if it is in fact a wrist pin/rod bushing problem...case comes apart. Best case is that you may need a replacement piston/cylinder, but you don't want to put it all back together and find out it's deeper inside. I would suggest tearing it down ASAP and doing LOTS of forensics along the way.
Good luck.

[uwanna]

I've had a wristpin noise very much like yours. DANGER, WILL ROBINSON!!!.
Here is a pic of my "wristpin noise". Yes the wristpin broke in two!!

Not only did it break the pin, but wallowed out the pin bushing in the rod, and due to the piston wobbling around, it also wore the cylinder into an egg shape.
Funny story how this happened. Back in '72, my girlfriend and I were on the way to the inaugural "Willy Nelson 4th of July Picnic" at Dripping Springs, Texas,in my prized '68 911. We got stuck in a 20 mile traffic jam that was moving about three MPH in 98 deg plus weather. After an hour or so of this nonsense, my oil temp went up above 360 deg.
I panicked and pulled over and left my Pcar in an open field. We then hitched a ride in the back of a pickup truck and got to the concert. Got a lift back to the car the next morning and drove her home, seemingly AOK. Then I started to hear the "rattle" at different RPMs. I took it to a fantastic mechanic friend of mine, and he said, "if I was you, I'd not drive any more, and tear it down". So I did!
Back then, the only thing I could do to a 911 was change the plugs and oil. So I got the workshop manuals and proceeded to get an education! When all was said and done I had Ray Litz at Competition Eng bore out the case for 88mm jugs (2.5ltr) and redo the heads for me. Got it all together, and presumably, it's still cruising around San Antonio Tx today with a happy owner.

[sjf911]

Originally Posted by Bob Kontak

+1 That is some serious decifering - how did you do that?

You cannot grind an SC cam to 964 dimensions. The 964 cam has a little more lift and a little more duration. That means welding metal onto the lobes then grinding.

They can be ground to 964 lift specs, just not much more. I had mine done by John Dougherty Dougherty Racing Cams

[db_cooper]

Originally Posted by prebordao

A few weeks ago I noticed some oil coming between the barrel and head in cyl#2 (just like in picture).
Removed the valve cover and I was able to torque the nuts a little more...
Question: Could it be the nuts unwinding a little over time, or the threads are beginning to pull ??

That is a good question..many engines need the heads re-torqued..things settle after thirty years.

Be sure and use a torque wrench...if the studs are pulling..the torque wrench would be your first clue.

I like the dial type than the clicker style...you can see and feel the tension.

[poorshe911]

Ok, it's a done deal. The motor comes apart now.

I've done quite a bit of mechanical work and saw a mechanic go through my old 2.7 but never tore down a 911 engine myself. It looks like an enormous undertaking. I'm inclined to have my mechanic do it. He's has lots of experience with Porsche engines including building race engines.
While trying to keep the cost under control do you think the motor will benefit from the 964 cam grind using the CIS? As I mentioned, I do have a euro fuel dist and SSI's. Also, have Carrera tensioner's.

Would you do a top end rebuild or split the case even if you didn't have to?
What else is a good bang for the $ upgrade while it's torn down?

Thanks very much.

[uwanna]

Originally Posted by poorshe911

Ok, it's a done deal. The motor comes apart now.

I've done quite a bit of mechanical work and saw a mechanic go through my old 2.7 but never tore down a 911 engine myself. It looks like an enormous undertaking. I'm inclined to have my mechanic do it. He's has lots of experience with Porsche engines including building race engines.
While trying to keep the cost under control do you think the motor will benefit from the 964 cam grind using the CIS? As I mentioned, I do have a euro fuel dist and SSI's. Also, have Carrera tensioner's.

Would you do a top end rebuild or split the case even if you didn't have to?
What else is a good bang for the $ upgrade while it's torn down?

Thanks very much.

If you are a good mechanic, and have a good set of tools, give it a whirl yourself!
I tore mine apart without ever seeing a Pcar motor, "guts and all". With a Bentley service manual and some reading and wrenching on your own, you can save a ton of money and have a very fulfilling experience. After all, there is nothing magic about these motors, they're just a collection of nuts and bolts and aluminum/magnesium just like any other motor! As far as how far to go with this project, I would recommend doing a valve job/guides , rings, etc. As to a case split, it all depends on what problems you find. If indeed you have a piston pin problem and need to rebush the rod small end, don't know how you could do that without having the rod out. Ergo a case split. Chime in if you have better suggestions folks.

[ant7]

Originally Posted by uwanna

If you are a good mechanic, and have a good set of tools, give it a whirl yourself!
I tore mine apart without ever seeing a Pcar motor, "guts and all". With a Bentley service manual and some reading and wrenching on your own, you can save a ton of money and have a very fulfilling experience. After all, there is nothing magic about these motors, they're just a collection of nuts and bolts and aluminum/magnesium just like any other motor! As far as how far to go with this project, I would recommend doing a valve job/guides , rings, etc. As to a case split, it all depends on what problems you find. If indeed you have a piston pin problem and need to rebush the rod small end, don't know how you could do that without having the rod out. Ergo a case split. Chime in if you have better suggestions folks.

+1
Sound Advice.
Anthony.

[poorshe911]

If I do take on the rebuild myself, living up here in western NY would probably mean I'd have to get the engine into my basement and work on it over the winter.
I have a walk-out basement but the door is only 32". Without doing some difficult measurements with the motor in the car, do you guy's think the motor would fit through the door?

What special tools/equipment would I need? ie .. engine stand, measuring devices, wrenches, etc.

Thanks

[Bob Kontak]

Not knowing the config of your house, you could mount it on the stand outside and spin it 90 degrees and get it through the door with a friend's help. Once on the stand, it is pretty stable and easy to move around.