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Premium Member
1983 380 SL
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3,490 Posts
More table space set up.



Removed the rocker arms.



This was a good investment.



Next I decided to get the dip stick tube out of the way.



It came out easier than expected.



Then the tensioner.....



...and manifold.



Using a strong magnet to ensure the chain circlips don't go missing.



Releasing the cam shaft bolts.





Removing the chain guides, these ones are ten years old.



Not much wear.



Refreshing my memory before taking the heads off.



First head, cylinders 5 to 8.



Other head, cylinders 1 to 4, you can see cylinder 1 which had the valve guide problem has the most build up and is oily.



Surprisingly, it also has the cleanest piston???



The bores all look in reasonable condition with the cross hatching still visible to some degree.





Curved guide removed.



That's it for today.



I did try to remove the front cover, all the bolts are out but it didn't want to come off so I will investigate more tomorrow. Perhaps the oil pan needs to come off first.
The front cover won't come off until you remove the oil pump chain. In order to get the oil pump chain off you'll need to pull the pan. At least that's the way it was on my 380.

How were the head bolts to remove? Mine were surprisingly easy.

I love that yellow tray for the cam and lifters. Where did you get it? I used paper cups.

It's weird seeing crosshatch on the cylinder walls. There is no crosshatch on 380 alloy engine. Well... except for my #6 where I had a sleeve installed... that one has crosshatch.

I don't envy you your cleanup job... I'm assuming you will clean everything... right? :unsure:
 

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Premium Member
1983 380 SL
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3,490 Posts
Don't be ridiculous, just thinking about future projects if I can pick up a cheap 500 engine.
Ya know... I was actually considering picking up cheap old Mercedes V8's and rebuilding them for sale. Luckily I got over that itch.
 

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Registered
1979 450SL UK spec
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1,764 Posts
Discussion Starter #83
The front cover won't come off until you remove the oil pump chain. In order to get the oil pump chain off you'll need to pull the pan. At least that's the way it was on my 380.

How were the head bolts to remove? Mine were surprisingly easy.

I love that yellow tray for the cam and lifters. Where did you get it? I used paper cups.

It's weird seeing crosshatch on the cylinder walls. There is no crosshatch on 380 alloy engine. Well... except for my #6 where I had a sleeve installed... that one has crosshatch.

I don't envy you your cleanup job... I'm assuming you will clean everything... right? :unsure:
Thanks, funny, I was just reading this when you posted, I had a vague memory that you had run into the same issue.


Head bolts were no problem, think I will be able to reuse, seems like the iron block give less problems than the alloy block.

The component organiser is great and fairly cheap.


Yes, the clean-up and plating will be a big job, glad you did the trailblazing!
 

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73 450sl with SBC motor and trans
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145 Posts
The front cover won't come off until you remove the oil pump chain. In order to get the oil pump chain off you'll need to pull the pan. At least that's the way it was on my 380.

How were the head bolts to remove? Mine were surprisingly easy.

I love that yellow tray for the cam and lifters. Where did you get it? I used paper cups.

It's weird seeing crosshatch on the cylinder walls. There is no crosshatch on 380 alloy engine. Well... except for my #6 where I had a sleeve installed... that one has crosshatch.

I don't envy you your cleanup job... I'm assuming you will clean everything... right? :unsure:
That is a sweet parts holder. I used a piece of 2" thick blue foam board and poked holes with all the parts numbered. I also got a table top 10 gallon parts washer and used a kerosene and simple green solution to wash all the parts.
Really enjoying this thread. Thanks for posting all your project.
Steve
 

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1979 450SL UK spec
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1,764 Posts
Discussion Starter #85
Sump off first thing today.



There were a few plastic bits in the cruddy oil at the bottom of the sump.



Bits of chain guide rail.



It is what it is.



Oil pump off.



I couldn't get the front cover off till I spotted this bolt.
:doh:




The lower chain guides which have never been changed in 41 years.





The oil pump chain looks to be in good condition, all the links are tight so I wont replace unless there is good advice to.



Timing cover with the idler wheel at the top and distributer cog on the left.



Lucky I bought a new idler wheel, two broken teeth.



Oil pump chain tensioner also 41 years old and worn.



Measuring the big end end axial float and then crank axial end float.

Crank was 0.21mm vs limit of 0.3mm

Big ends were 0.29 to 0.33mm vs limit of 0.5mm



Pulling off the crankshaft sprocket.





Seven of the pistons were 91.99mm.



Just one was 92.05mm, which is at the large end of the standard sized pistons.



The last thing I did was remove the first big end bearing cap nuts, but the cap didn't want to come off. I gave the studs a light taps but it didn't break free. Any suggestions on how to free it off without damage?

 

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Premium Member
560SL 1986 244k miles astral grey / black
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440 Posts
This is soo cool! 👌
 

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Registered
1974 450SL (US), 2005 SLK200 (UK)
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600 Posts
If you are going to all of this effort why would you not change the oil pump chain? I don't know the cost but must be less than a timing chain I would have thought? Not saying you should - just curious.

Andy
 

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1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
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7,335 Posts
When my 380SL was converted to Dual Row Timing chain at 38K miles, they replaced the Oil Pump Chain too. Back then I would have thought that chain should be Dual Row too but was told the Oil Pump does not put that much stress on the chain.

Still enjoying following your rebuild.
 
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Premium Member
1983 380 SL
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3,490 Posts
The last thing I did was remove the first big end bearing cap nuts, but the cap didn't want to come off. I gave the studs a light taps but it didn't break free. Any suggestions on how to free it off without damage?

Put the nuts back on but not far enough to expose the threads, then give the nuts a good rap with a brass bar. They'll break loose.
 

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1979 450SL UK spec
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1,764 Posts
Discussion Starter #93
I removed the pistons first today, the caps are held on tightly even once the nuts are removed, an interference fit between the cap and the lower portion of the studs. It took a bit of courage to separate the first one.



There is some slight scoring on the top side of the pistons, I was surprised that the underside was clear. Left bank viewed from the front of car.



Right side.



Main bearing sizes, only four shown but there are five bearings?



Before removing the caps I made this video.




Crankshaft lifted out.







After I measure the main bearings and piston bores I plan to send the block out to be cleaned at a machine shop, should I remove the pressure release valves or is it ok to leave them in place?

These two are the main over pressure release valve and the oil cooler over pressure valve.



This one is the oil filer pressure relief valve.

 

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Premium Member
1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,893 Posts
Love your pictorials etc ! I suppose one benefit of the lock down is you get to go on this great adventure ! But IIRC you already got COV19 and recovered ? Maybe it was someone else.?
 

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1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
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7,335 Posts
Never attempted an Engine Rebuild ... but I find your process interesting.
Imagine what it would cost to pay someone to do what you are doing ... ouch!!
 
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1979 450SL UK spec
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1,764 Posts
Discussion Starter #97
Some measurements today.



Micrometer set to 92mm.



Bore gauge set to zero in the micrometer.



These are the measured values at the top, middle and bottom of the bores in both the transverse and longitudinal directions. The measurements were taken at 13degC rather than the specifications which are probably taken at 20degC.

I have made an estimate of the for the likely values at 20degC but am not sure how accurate this is given the micrometre is also calibrated for 20degC.

Let me know if you think I should use a different value for cast iron.

The bore wear limit is 0.1mm just below the top ring, so it looks like I am well below this limit across all cylinders.



As for the pistons, the measurements are below. I was really surprised how much under the spec value they were, so I brought one into the house tonight to make a comparative measurement at 20degC and found the piston skirt on piston 1 was 0.025mm larger than at 13degC so used that value to adjust all the values. Ad the pistons are tapered, the bottom of the skirt measurements are the only ones that really make any sense.



So the bottom line of what I was wanting to check was the piston-bore clearance which has a spec limit of 0.08mm. From the table above you can see that piston 4 is the only one out of spec. However I am not really convinced that my measuring methodology is good enough.

It is also a PITA that the factory fitted the wrong pistons in positions 1 and 4, the marking on the block calls for piston code "2" and piston code "1" was actually fitted, that adds to the excess clearance.

Given standard size pistons in any group size are no longer available, fitting a larger group size piston is not an option.

Boring out the block to use the first repair stage pistons (92.5mm) would cost at least £1200 for the aftermarket pistons and machine work, for me I don't think it's worth it for one marginal cylinder.

What are your thoughts, please also offer any advice on my calculations.
 

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Premium Member
1999 500SL, 1988 SEC
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1,530 Posts
Ok, this is just me. I think you are getting into too much minutia for what you are doing. I assume you will keep the car for a few years as a weekend driver and as such wont put zillions of miles on it. So longevity is not critical. Your bores look good so leave those. If and this is a big if, you could find a set of correct pistons without the skuff marks that would be great but not critical. Where I would spend my time is 1 replace the bearings only because its apart, 2 have a valve job done, pay attention to the length of the valve stems, 3) replace the rubber bits, 4) replace the timing chain items, 5) front and rear seals, 6 head-gasket. Doing all theses would give you many many more miles at a nominal cost
 

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Premium Member
1983 380 SL
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3,490 Posts
Having just gone through this with my 380 (88mm pistons instead of 92) and having considered most of the same things you are talking about... I arrived at the following conclusion... it ain't worth the worry to worry about tenths (.0001) of an inch on an engine that (in my case) was 36 years old and was running fine before I took it apart looking for a reason it was ticking. Of course mine had a blown piston and cylinder but other than that the rest was in pretty good shape, (if you don't count the fact that "all" the bearings were shot).

There's only so much you can do without painting yourself into the perfection corner... perfection is the enemy of progress.

If it were me (and it was) I'd change all the rings and bearings and put that cast iron beauty back together. Redo the heads for sure... it's easy. You can re-seat the valves using the old fashioned rubber cup and valve grinding paste method and replace all the valve guides (I made a video) and valve seals.

Send the block out to be cleaned for sure... I did and I'm glad I did. As long as you send it to a good shop it will come back looking new. You might consider having the cylinders honed to restore the cross hatch (if they're gone) but that's as far as I'd take it. You're not building a 2000hp dragster engine, it's a classic roadster engine at 225hp.

Love your work... keep those pictures coming... they make my day. :)
 

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1979 450SL UK spec
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1,764 Posts
Discussion Starter #100
Catch up for the last couple of days.

I gently cleaned up the decks.



Checking the decks for flatness with a straight edge.



The thinnest feeler gauge I have is 0.04mm and that would not fit under anywhere.



The same for the main bearings with the old shells.....



.... and without the shells.



Moving on to measure the crank pins and main bearings.



Then finally heading off the the machine shop.

 
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