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  #1  
Old 06-27-2006, 11:11 PM
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Location: Texas
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350sl w/116 - head gasket blown?!?

I recently purchased my first MB (what I thought was a 1977 450sl only to find out it is really a euro 350sl, 107043 w/ 116984 engine) that had sat for 5 years. After completely cleaning and replacing every fuel system part from inside the fuel tank to the fuel distributor to get it running, I find I have a blown head gasket.

Never having tackled this job before I took it to the local euro mechanic and he wants to rebuild the whole thing $$$! The left head is trashed and the right one looks rough so I can see getting rebuilt heads but do I need to go into the crank & pistons? They are afraid the water/head problem may have existed for a while before it was parked and this may have done unseen water/oil damage to these internal parts. I don't want to spend a ton of money but don't want to make a poor decision while it's torn down.

Other recommendations from the shop were to replace the old A/C compressor & clutch assy. while we are in (it's a manual 4 speed). Also, the motor mounts, timing chains & guides... you get the picture. How much should I do?

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'77 350SL, Euro-Manual
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Old 06-28-2006, 01:08 PM
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Painful as it is, this sounds like realistic advice.

You could wait until the heads are off to assess the pistons and block, but then if the engine needs to come out you will have to pay more because it takes more time to pull the heads with the engine in the car.

For what you will end up paying, you might want to consider a used engine, or maybe even a rebuilt long block. This would be more cost effective than paying shop rates for a rebuild, especially if you can pull the engine yourself. Metric Motors and Adsit can probably help you with a rebuild.

Good luck,
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Chuck Taylor
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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Old 06-28-2006, 01:17 PM
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3.5 V8

That's actually a very sweet engine from what I understand and if it's a Euro it's going to be a lot more fun then the US spec 4.5 engines. You can look around for used 3.5 heads or alternatively buy a set from Germany. If you surface / sea freight them, shipping should not be too bad.
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Old 06-28-2006, 02:53 PM
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These heads - if not rebuildable - will be very difficult to find in the US (K-Jetronic cutout, 3.5 heads with hydraulic ball studs). You COULD substitute US 4.5 heads of the same vintage but you WILL have MUCH lower compression (think about 7.5:1). Your best bet - if the heads themselves are not rebuildable - is to find an older 3.5 engine with good heads and cams and swap those into your engine (if not swap the entire engine). You might need to work on adapting the injectors to D-Jet heads but that'd be the trickiest part.

You have an extremely rare vehicle and I would love owning it if I were you. However, you can NOT own such a vehicle without expecting to spend TONS on repairs for it if you can't do them yourself, simply because parts specific for its engine will be VERY rough to get in the US.
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  #5  
Old 06-28-2006, 07:22 PM
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Quote:
You could wait until the heads are off to assess the pistons and block....
Yes and doesnt the status of the bores even on visual inspection reveal condition of the rings? Meanwhile I've never heard of MB crank and bottom end bearings giving up easy.

Hell, if it was me I'd change the oil and deffinitely run a wet/dry compression test ASAP - even with the engine idling/operating under blown head gasket conditions. That oughta be the first and best diagnostic step anyhow to help figure out what the rings are doing at least. Also to help tell you exactly how blown that headgasket is. And how's your oil pressure?

I hate it when mechanics start selling astronomical repairs to finicky types (am not adressing anybody personally) treating these as "fragile" automobiles. Truth is the Stuttgart shortblock is tough as nails.
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  #6  
Old 06-29-2006, 09:33 AM
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Thanks Dog...

I agree. From all I've heard the bottom shouldn't fall out if I just repair/replace the heads. Oil pressure was good and I changed it before drivng it at all. The symptoms were vapor in the exhaust after running a few minutes and getting hot (overheating), and there was water in the oil. The problem is that the car sat up for five years and this may be why but I don't know. The blown gasket may have just occurred, but it may have been driven in this condition for a while.

We will see!
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Old 06-29-2006, 09:47 AM
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My concern was that the head gasket occurred before the car sat and leaked into the cylinder causing corrosion problems in the cylinder wall. I have this nagging feeling that the car was put away because of the head gasket problem.
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #8  
Old 06-30-2006, 07:49 PM
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There's a 350se sedan in PA that's been for sale at http://www.collectorcartraderonline.com/advancedsearch.html for at least a year if not three. That would supply you with a good used motor. To swap it into your car, you'll have to change the oil pan, the oil filter mount and the flywheel assembly.

That or use its heads and rebuild your motor. I'd go the used motor route, but that's because I do my own work.

-CTH

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