Rebuild 2.0 1968 S Motorsheister autopsy part 2 (finally)!

docrodg · 04-09-2010, 01:40 PM

OK... trying to continue along with what I started way back in October. Since then I have had some tough times and not able to get to any of this. To sum up look at the original post rebuild 2.0 1968 S Motorsheister autopsy and add since that fun time a complete remodel, full gut and rebuild of the bathroom on a 120+ year house, ball-freezing winter, 3 weeks helping my mother move, removal of 1/8" off the tip of my left thumb (from helping mother move), 1 week in Shanghai, and other assorted fun.

So, to update on the findings of this work, I am currently in the "clean and measure" phase of this. All measurements I take here are using calibrated equipment with NIST traceable gage blocks. In fact, I found that my inside mic was out of cal and had to adjust it!

First stop, Pistons/Cylinders:

A bit of carbon for so few miles... did those morons clean it???

Cylinders: All measure between 80.010 and 80.015 with 0.001 or less eccentricity (out of round) and the same for taper. Some minor wear marks on the sides of the bores as seen in these pics, but the original honing pattern is still visible.

Pistons... Here is a clean and unclean comparison. All are not yet cleaned up. Measure on the skirts at the required 1.5mm up dimension are 79.9746 to 79.976

As you can see the piston number is for a 69 S engine... another part change from those *&%*%$^$&^%#$@!@#%%$!

Our next stop: Rocker Arms and Camshafts! Followed closely by my favorite liquor store!

docrodg · 04-09-2010, 01:58 PM

OK... Most rockers are in appearances not too bad. Invoice from MotorSheister says one used cam was installed and three used rocker arms. If you ever wanted to know how to tell which three were replaced then just look at these pics.

Bad Camshaft, The wear on the worst-looking lobe is .020 inches. The other cam is the original one and is fine, and part number 901.105.183.0R casting date 2-1-68. This is the replaced used cam, part 901.105.110.0R casting date 10/24/68.

This is what .020" wear looks like:

Nice faceting:

docrodg · 04-09-2010, 01:59 PM

So, a bad camshaft (probably not hardened prior to install)... so lets take some used rockers and use those too! 3 lobes were found to be very excessively worn, the same ones that had horrible valve lash (see original post, but 3mm is over)...

The worst rocker besides these 3 (and thus reason they are known to be the replacements):

Still measuring and cleaning, I will have a final spreadsheet of all measurements when I am done that can be posted, but this is not easy work with one thumb wrapped in gauze and hurting.

This weekend: measuring piston grooves and head disassembly, followed by a trip to my favorite ammunition store!

Steve F · 04-09-2010, 02:11 PM

Just WOW

kenikh · 04-09-2010, 02:45 PM

Ah, finally...

Augustus · 04-09-2010, 05:24 PM

dude...get a better camera...

docrodg · 04-09-2010, 08:47 PM

hmmm...buy a better camera or parts for the 911...

calling911 · 04-10-2010, 06:05 AM

So you tore this down cuz she was smoking right? find the reason? Sounds like it ran fine beyond that.

Does it matter that you had S pistons.. were they all S? Was the compression the same if they were different?

David · David's Garage

So 1,530 miles after the rebuild and there's a worn out cam and rockers!!!

How do these guys stay in business?

docrodg · 04-10-2010, 06:24 AM

Quote:

Originally Posted by calling911

So you tore this down cuz she was smoking right? find the reason? Sounds like it ran fine beyond that.

Does it matter that you had S pistons.. were they all S? Was the compression the same if they were different?

No... it was torn down because it sounded horrible. So much valve train noise and a possible rod knock, plus it was known to have been a questionable rebuild.

Pistons should have been "S" pistons... it is a 911S. Just that the pistons in it are from a 1969 engine, not the 1968 that it is. Compression should be the same, Mahle lists these pistons as replacements for a 1968 and the ratio is same between the years.

docrodg · 04-10-2010, 06:27 AM

Quote:

Originally Posted by 125shifter

So 1,530 miles after the rebuild and there's a worn out cam and rockers!!!

How do these guys stay in business?

Worn out??? Look at those pics! Those are beyond worn. If anyone here ever questioned why you never mix cams and rockers and if re-using a camshaft without refurbishing you must use the old rockers this is the proof.