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Rebuild 380 engine for '81 380SLC? - What was I thinking??

22K views 136 replies 29 participants last post by  Jyuma 
#1 · (Edited)
I went and did it! I have an '81 380slc that I just love, but the engine died with 265K miles on it. It burned oil, ran very smooth, but lost all power. A check of the compression revealed that most of the cylinders were in the 60 PSI range.

I could not bring my self to junking the car and after researching all the threads in this and other forums, I decided that I was going to rebuild the engine, and not just rebuild it, but do the job to original OEM specs complete with the Alusil lapping of the cylinders. These cars are pretty rare with only 1,500 imported to the USA. With the natural attrition from being wrecked or worn out and abandoned or most likely torn apart from the inside as a result of the single timing chain, my hope is I'll have a rare classic that is both fun to drive and maybe worth keeping.

The story is further complicated by the fact that the transmission leaks like sieve, so that is going to be dealt with too.

I hope to keep those who are interested in doing something like this informed so they can make their own decision whether or not they want to try this. --Finally I would welcome feedback from others on their experience in working on their engines as I rebuild the engine.

This is going to be an ongoing thread over the next several weeks.

So here are copies of my invoices detailing my decision to go down this path.




This is the block I got back.





In the words of my favorite comic, "And away we go!"

Tomorrow I will discuss my choice of machine shops.
 
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#2 ·
Good show. To make you feel better I ought to show you my invoice of
$6,000 to convert my 1983 380SL from single row timing chain to
dual row timing chain.

Looking forward to your rebuild progress.
 
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#32 ·
Now for the timing chain, rails and cover....



CWMoser, I am now in the timing cover doing what you had the prior wisdom to do! I think you did the right thing. I'd take a one-time punch of $6K any day over the slow drip of one problem after another that I have been going through with my car. I short-sightly elected to follow one fellows advice to just renew the chain every 35-40,000 miles. Problem is you don't necessarily renew every other integral part; if a guide fails the fact you have a new chain does not matter. In 2008 my single link chain jumped the cam sprockets tore apart my engine, and did at a time most inconvenient for me. I ended up replacing several valves, redoing the heads, replacing the timing chain components, but not the deep down chain guides that also get old and brittle. I never fixed the real problem-a single timing chain. I sincerely believe my engine would have lasted another 50-100,000 miles if I just did what you did. Bully for you.

So, today I wanted to get the timing chain and cover, its guides, and dual intermediate gears installed. If time permitted I should also be able to install the oil pump.

Alas I was not able to get this all done.

In dry fitting the timing cover, I was again impressed with Sergio's attention to detail. Note that the timing cover is machined to fit the top of the block. I would have never thought that necessary.
 

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#14 ·
Rare does not equal valuable.
So true. IMO the term "rare" is overused here. None of our cars are rare in the collector world where value is determined by one of xx or one of xxx...not one of xxxx or more. The only possible exception is the 560SL AMG rumored to be three made...emphasis on the rumored.

As far as the high mileage award goes if that is what you are into go for it. It all depends on the availability of parts and how deep your pockets are.
 
#4 ·
I recommend adding your images to your posts....all too often links to images go away when accounts change or other factors. If they're part of the forum they will be there as long as the forum exist.

...also you don't have to click through to another site to view.
 
#5 ·
You are 100% correct!

These cars are pretty rare with only 1,500 imported to the USA. /QUOTE]

Rare does not equal valuable. Too bad you didn't invest the money in a 107.026.
I have read the Moser post about spending 6k to upgrade the timing chain and cringe.
I assume he got Benz to do it for free under some warranty.

People ask a lot of Money for these SL's but only a handful sell for 20k plus.
They built a lot of cars----

Some people told me I sold my pristine 83 for too little! Sold in a day for $ 8500---but it SOLD.
Think it wasn't a nice car? Go to CL jersey shore---for a bunch of pics--it is still sort of listed to
advertise the parts I have to sell. CASE CLOSED! MY mileage was totally documented not BS stories as to why these cars have super low mileage. Speedos break and they weren't fixed for years. The ads sure do get creative as to the reason for low miles.

Final point---know why only 1500 of the cars were imported? That's all they could sell!

You can't really afford to redo these cars unless they really have some sentimental attachment that will override the financial decision.




IMO-I totally agree with Rowdie---
 
#12 ·
I would be interested in following your progress on this project. The Euro 380s had higher horse power. I wonder what it would it would take to Euroize an North American 380.

I applied for my cars High Milage Award a couple of months ago but haven't seen anything on it. How long did it take to receive it once the application was mailed in?
 
#13 ·
I have a set of cams out of a 1981 380SL Euro engine if anyone wants
to try.
 
#16 ·
That is a beautifully clean Engine Block.
Post as many pictures as you can --- its a lot of eye candy to most of us.

I will say from my experience with my 1983 380SL, that a well tuned 3.8L
engine really does perform very nicely. I got mine running great and its
the USA so called low power variety. When you get your Euro 3.8L engine
running with all the work you are planning, I bet it will feel even better.
 
#17 ·
Before I get to today’s work I like to share what I have learned about the choice of machine shops. Do not do this job unless you have identified a shop that has experience with Mercedes or other high end import imports As most of you probably know, but for those who do not, OEM Mercedes engines have an Aulsil silicon coating the cylinders. Apparently the pistons and rings ride on this coating with little or no wear to the aluminum block. This is why these motors last 250K+ miles. Your shop has to have experience in this process. There is absolutely no way your engine will last any length of time unless this coating is properly applied in the cylinders.

I live in the Southern California area and I identified three nearby shops who professed experience in Aulsil. They are: Costa Mesa Automotive Machine Shop. (Costa Mesa R&D) ; Metric Motors in Canoga Park, CA (http://mercedesengines.net/); and the one I ultimately chose, Motor Works in National City, CA (Motor Works, Inc. - Auto Machine Shop | National City, CA). Costa Mesa game me a quote on the block of $1,000. Metric’s quote was in the short block was in the $5800 range, and Motor Work’s quote was also in the mid $5’s. My choice of Motor Works was solely driven by personality of the owner Sergio. When I explained that $5600 was a little rich for me, Sergio, the owner, responded, we can work that out. As you can see from my invoice, we did.

A little about Sergio the owner of Motor Works: he is in his 80’s, and a spry 80’s at that! Born in Italy, was taught his trade in France and finally immigrating to the US in the late 40’s early 50’s. He has been rebuilding European motors since he was 14. How do I know this? Sergio was more interested in knowing about me than the car. European’s do that; they decide if they want to do business with you and once you they decide to nothing will stop them. Once he turned his attention to the motor I was astonished with his forensic skills. There is nothing more humbling than being in the presence of one of these apprenticed masters. The engine was in pieces, pistons here, blocks there, rings in another box. By looking at the rings, pistons and cylinders walls he was able to tell me exactly what was wrong with the car. He also quickly identified (to my humiliation) the major problem with the block---ME!

The one bone headed thing I did when pulling my original engine was to pull the pistons and crank shaft. Big, Big mistake. "Huuuge" mistake. I used a standard ridge reamer to remove the cylinder ridge only to destroy the block. The aluminum cylinders are extremely fragile and damage to the top was greater than could be rectified with an over-sized piston. So the lesson is tear your block down to the pistons and crank shaft and then take it to the shop. --There is a definite point where the amateur needs to defer to the professional.

I welcome your feedback and comments.

More to come….
 
#20 ·
Yea, I ruined my old block. The one in the pics is a replacement. If you look at the invoice it has line for "Good used Block $380" The irony of that didn't hit me until way later... How do you price a used 380 Block? Simple $380.00 Glad I did not have a 560!
 
#24 ·
Today's assignment is loading the crankshaft and pistons. Pretty straight forward, but here is some additional background.

In talking with Sergio Bartolini, my new best friend. I learned that the supply of rebuilt pistons and other specific parts for these engines is running low. I was always under the impression that the pistons could be reused, however that is not the case. The cylinders are honed to the next repair stage and pistons that fit that bore are used. Almost never are the same pistons recycled in the engine. In my specific case the bores are honed to the first repair stage and each piston (and its rings) are selected to fit the bore.

You can see by the block that the bores were orginally 2+ and have been bored to the first repair stage 87.998 - 88.003 with pistons sized 87.985 - 87.990. Each piston and its rings are then matched to the cylinder and identified. Anyway, I had to put specific pistons in specific cylinders. The tolerances are truly tight.

With that said the only parts that I was able to reuse were the crank shaft and rods; everything else is new. Indeed the cost of the new pistons ($185) is the largest single line item in the invoice.

I used an old garden glove to protect the cylinder walls from being scratched by the rods. A standard ring compressor to insert the pistons. The pistons all slipped in with more ease than I expected. The rods bolts are torqued to 50 nm and then angle torqued 90-100 degrees.

Voila! The pistons are in!
 

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#26 ·
I was always under the impression that the pistons could be reused, however that is not the case. The cylinders are honed to the next repair stage and pistons that fit that bore are used. Almost never are the same pistons recycled in the engine.
If you've ever heard the phrase "bored 30 over" or "bored 60 over" that is what they are referring to. When a block has been bored .030 over usually that means it is the first rebuild. There is a limit to how much you can over bore a block before the cylinder walls become too thin. It also adds to the displacement of the engine. A 350 Chevy engine bored .030 over would then displace (ballpark) 355 cubic inches.
 
#27 ·
First rebuild issue

With the pistons in my first unknown on this engine involves the rear oil seal and its mating surface on the crankshaft. After polishing this surface with a fine grit emery tape, I noticed a very small grove the old seal had worn into the surface. To my surprise during dismantling the engine I found no leak oil from the rear seal (it leaked like a sieve from the transmission pump, however). The groove is pretty small and not too deep.

So my question is do I need to find a repair solution? I know national and timken sell repair sleeves that fit over the seal counter shaft.

Your thoughts...
 

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#30 ·
With the pistons in my first unknown on this engine involves the rear oil seal and its mating surface on the crankshaft. After polishing this surface with a fine grit emery tape, I noticed a very small grove the old seal had worn into the surface. To my surprise during dismantling the engine I found no leak oil from the rear seal (it leaked like a sieve from the transmission pump, however). The groove is pretty small and not too deep.

So my question is do I need to find a repair solution? I know national and timken sell repair sleeves that fit over the seal counter shaft.

Your thoughts...
OK, Here is the authoritative answer.

I called Motor Works in San Diego, The ridge on the real bearing seal surface is not deep or significant. It is OK to leave the sealing surface alone and not repair the surface with a sleeve.

Now for the new work.

I purchased a new crank Woodruff Key and installed the dual chain crankshaft sprocket. The sprocket was installed by heating it in my oven to 350 degrees and then taping it on the crankshaft with the woodruff key underneath in the crank slot.
 

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#33 ·
After dry fitting the timing cover I installed the front oil seal, the replacement oil pump chain guide, the chain guides and timing chain.

Also not the old single and new dual chain intermediate gear. The old single intermediate gear has considerable wear in the chain sprockets. Just another component getting ready to fail.

I installed the dual chain links. I hate these little C clips they always spring off to some dark corner of the garage.

Note the old (broken) and new lower chain guide. More evidence that CWMoser did the right thing by upgrading to a dual chain.

However, to my surprise I noticed that one of the bolts to the timing cover was broken off and needed to be removed prior to installing timing cover. - Two drill bits later and several hours the pesky broken bolt was removed with no damage to existing threads.

Tomorrow I hope to properly install the timing cover and maybe even the oil pump.
 

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#35 ·
Thanks for those photos. I wish I had your expertise to do this work myself.
Photos of a nice clean engine are good for when one needs to fix something later.
I would take a lot of photos of the back sides and bottom and save them.
 
#37 ·
Moving to install the timing cover.

I finally got the timing cover installed. I failed to recognize some important dependencies of the timing cover. First the water pump must also be installed along with most accessories along side the left and right side of the engine.

The new water pump arrived this morning. Anyone who is familiar with this engine knows what a pain it is to replace a defective water pump. I don't want to see the front of this engine for 75-80,000 miles and while the old pump looked pretty good, it is being replaced.

The first step in installing the cover is making sure the intermediate gear is properly aligned. Notice the red line showing the alignment of the intermediate gear. There is a mark on the block that the intermediate gear must align with.
 

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