Engine Rebuild Hic-Cup

[JimVillers]

Bob Hyatt, Gary Tyre and I are rebuilding Gary's engine and restoring the engine compartment.  I have the engine on an engine stand and have "everything assembled" (head, manifolds, injection, water pump, power steering pump etc).  I left out the tachometer drive so that I could turn the oil pump with an electric drill to get oil pressure before installing the engine and turning it with the starter motor.

Now the issue.  I just tried to install the tachometer drive and it appears that it needs to be installed before the head is installed.  While I don't see any solution except pulling the head, I though I would ask to see if anyone else had done this and found some magic.

[mdsalemi]

Ouch.  Good luck with that...

Try a call to Metric or Noel's and see if they can shed any light for you before your wrenchs start turning again...

[stickandrudderman]

YOU DO NOT NEED TO REMOVE THE HEAD!
The tach drive has a collar around the base that looks like it's part of the drivebody, but it's not. Once you've identified it you can slip it off and install the two components simultaneously.

[bpossel]

Hi Jim,

A few years ago when I replaced my tach drive, Joe suggested putting it in the freezer overnight to shrink it a bit.  That worked and it really helped to install it...
Bob

[ja17]

Hello Jim,

You should never have to remove the head to install the bushing.  The clearances are extremely close.  I presume you are having problem getting the bushing to clear the cylinder head.

If the head has been machined, you can have even less room to install the bushing. At the PUb before last, I was helping Dan Caron install shims on his tach drive.  He was having the same difficulty. Finnally we filed a very small flat spot on the top rim of the bushing so it would clear the head. Worked fine, no problems.  We attributed the problem to the head being cut and reducing the room to install the bushing.

Now if you are able to start the bushing and have problems getting it to slide into the block, do as Bob P suggests to help shrink the bushing.

[JimVillers]

Joe, Colin et al .... Thanks for the input.  After looking closely at the bushing and seal, I saw what Colin was saying that the top comes apart.  That helped and makes it look possible.

I believe that there are two contributing issues.  The head was milled about 0.013 inch.  I also noticed from the wear marks on the drive gear that it is mating at the very bottom of the gear.  That would lead me to believe that the bottom bushing may not be fully seated.  If the drive gear dropped about 1/8 inch, everything might slip into place.  As it is, the collar does not drop down enough so that the set screw can go through the hole in the side of the collar.  Tomorrow, I'll try tapping the top of the drive gear to see if it will seat the bottom bushing a little further down so that the collar will sit low enough to allow the set screw to match the hole.  That will probably provide the extra to allow the top to slip into place.  If not, I'll grind a little of the edge of the top "bolt".  

It never occurred to me that the fitting of the tachometer drive have been a problem.  

I will add that the drive gear does appear to drop "a little" into oil pump slot.  I will also spend some time to insure that the oil pump is turning.    

There is so many more "details" and complexity in assembling this engine than the 190SL engines that I have done in the past.  We had all of the bright metal yellow cad plated and the engine looks wonderful on the stand.

[glenn]

Jim, How did you get the bushing out in the first place?  I have a couple of heads, but can't budge the bushings for the tach and oil pump?

[JimVillers]

Glen ... I didn't take out the bushing.  I had problems disassembling the engine (rounded pan bolts) so I just took it to my local machine/race shop to have them finish take the engine apart and do the machining.  Maybe the bushing moved during cleaning or other operations. 

[glenn]

Jim, A couple of questions--   1, Is the tach bushing a straight cylinder with no shoulders?  And sits on a shoulder under it in the block?  2, Is the oil pump bushing a straight cylinder also?  And rest on a shoulder above it in the block?

Looking at my engine I can see that there is little clearance between the bushing and the head as you try to slide the bushing past the head into the block.

[JimVillers]

Glen ... I think that the answer is "yes".  The top tachometer bushing is a silver cylinder that will just clear the head as it comes out of the block.  It looks like it is held in place by the set screw that goes through a hole in its side.  It looks like it should sit about 1/16 inch below the top of the head. 

The the bottom of the gear of oil pump drive/tach drive looks like it sits on the bearing in the block.  The top bushing then sits on top of the gear. 

With everything assembled, the top of the tachometer bushing sits about 1/16 above the top of the block and the set screw does not align with the hole.

I'll work on it tomorrow and let you know what happens.  If it doesn't fit better, I'll take some pictures to document what is happening. 

[66andBlue]

Glenn and Jim
here are a few photos that might help you getting the bushing in and out of the hole.
Sometimes the vertical gear doesn't quite drop down because it does not engage snug with the horizontal gear.
For reasons that I don't understand, it sometimes helps to rotate the vertical gear 180 degree and then insert again.
Also rotating the crank slightly to rotate the horizontal gear while you insert the vertical one can help.
It is absolutely necessary to get the set screw into the hole of the bushing housing.

[JimVillers]

Alfred  .... Perfect pictures and exactly what I am working on.  I notice that your oil pump drive gear also shows wear at the bottom of the gears so that must be normal.  The picture of the upper bushing flush with the block is what caused my concern.  Seeing that picture reassures me that things were not correct and that I need to figure it out.  More in a couple of hours.

I'll just say the obvious, this is the value of the club.  Knowledge, support and encouragement. Thanks.

[JimVillers]

Success ....... I first tried installing the drive gear and turning the engine ti see if the oil pump was being turned; it was not turning.  I then filed a couple of burrs off of the end of the drive gear and marked the direction of the slot on the top of the shaft.  After installing the gear, I rotated it to about angle of the oil pump ad tapped the top lightly with the wooden end of a small hammer.  I then rotated the crank a little and repeated the light tapping.  The drive gear slid down against the lower bushing.  I then fitted the upper bushing and it dropped down to where I could install the set screw into the hole.  The O-ring and top seal washer fit into the machined recess in the block and the top cap would now fit between the head and the tachometer drive.

Again, SUCCESS and thanks to all. 

[ja17]

Hello Jim,

Check the up and down play of the gear before finishing up. You may need a shim.

[114015]

Mensch Alfred !  

Dank Deiner Hilfe habe ich dieses so oft geschilderte Problem endlich vernünftig verstanden.  
Das steht mir ja noch bevor!
Herzlichen Dank dafür !


Just mentioned that this was great help of Alfred; I really appreciate it.

Best,
Achim
(useless engine parts collector)

[Benz Dr.]

I remember what Joe said when he checked the free play in my tach drive gears. '' Oh my.... !!! ''
I kind of knew it was loose but this one weas really loose.

When I rebuilt my engine for the second time I think I changed the bushing and sleeve that holds the gear in place and picked a really worn bushing. The engine made a very strange noise at start up then gradually went away but it always had that odd noise. When Joe checked the free play the shaft moved up and down about 10 mm! Normally it should have 1 mm or less.

I couldn't get the sleeve to remove so joe asked me to get a wrench for him because he was working on another car at the time. When I got back he already had the sleeve out. When I looked at it I could see he filed off of one side to make it clear the cylinder head. After we pulled the sleeve I could see it was heavily worn on the bottom side of the bushing. I used a file to remove the ridge and Joe brought a piece of sand paper so I could dress the end of the bushing. Using some WD40 on the paper and using a figure 8 motion it soon was smooth. We used two seals that are also used under the injectors to take up the play. These are copper and are fairly hard so they won't wear away very quickly. Normally, you should only need one seal - that's how worn this part was.
I'm quite sure that the gears were ready to start climbing or chip the ends off. The gear teeth should be centered so that maximum contact is on each side. The contact surface was probably only on the very last bit of the gear face and it's a wonder they didn't break. If the gears break the engine will continue to run but the oil pump will quit turning. If you're lucky the woodruff key on the distributor drive gear will shear off and the engine will quit running. As unpleastant as this might sound it's preferable to loosing oil pressure at 4,000 RPM in the middle of the night.

It's one of those things you simply wouldn't know about unless someone told you. By the time your engine failed it would destroy so many things the real problem might not be found and it could happen again if the gears were still loose. Somehow Joe figured out this simple repair so my hat goes off to him.
This is something I check on every car that comes in to my shop and all engine rebuilds get this treatment. Almost all of them need a shim to take up normal wear.

[glenn]

Here's what a 250SL looks like.  Block pix shows tach drive sticking up.  The other is the transition piece that screws into the block and is capped by the tach cable 'bottle cap'.

[66andBlue]

The "transition piece" is the same for 230SL (M127.II), 250SL (M129) and 280SL (M130) engines.
Sedans have no mechanical tach drive and a different cap as Joe A. posted here: http://www.sl113.org/forums/index.php?topic=443.0


He also posted more pictures of the other parts in this topic: http://www.sl113.org/forums/index.php?topic=3097.25

[glenn]

66andBlue,  How does one get the 62.7 mm bushing out of the block?

[hauser]

Alfred seems to have a picture for just about everything that is W113!  Great going Alfred!  Now that you have retired perhaps a How To Book complete with photos for the Pagoda!!

[66andBlue]

Glenn,
first loosen the 10mm hexhead set screw that holds the bushing,
then loosen the 22mm connector piece by about 2 - 3 turns and wedge a blunt chisel or screwdriver between it and the cover plate (washer). If the the connector does not want to move upward together with the bushing dribble some PB Blaster around the perimeter and also into the set screw hole. Tap/wiggle the 22mm connector piece and let it soak. Repeat, repeat, repeat ... until it moves. It took me about a week to get this one loose.  The engine had been sitting for a couple of years and all the lubrication was dried up.

[JimVillers]

The engine is about ready to install and I thought I would post a couple of pictures.

[ja17]

Hello Jim,

Looks great!  Although I don't care much for the ideal of putting it in a yellow Ford Mustang

[graphic66]

I had alittle play in my tach as mentioned above. Instead of putting a shim in between the bushing and the shaft I pressed the bronze bushing out of the aluminum sleeve and put a brass shim I cut out with an exacto knife in between the bushing and the aluminum body and pressed them back together. It is really easy to press them apart. I just tapped the bushing onto my brass shim stock to get an impression to use to cut the shim. I just cut a hole in it and left it square and after pressing it together I trimmed the excess shim away. It took a few pieces of thin shim, but it worked great.

[ja17]

Hello,

Yes that is actually the factory workshop repair procedure as long as you can get your aluminum and bronze bushing apart.  You should still smooth down the rough worn end of the bronze bushing. before re-installation.  It's your choice both methods seem to work fine.

I suspect that if you put the bushing assembly in the oven first, they would separate even easier since the aluminum has a higher coefficent of expansion than the bronze. Place in the freezer prior to installing the assembly in the engine.