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1979 450SL UK spec
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Is this what an engine looks like that's ready to start?
View attachment 2660649

How am I supposed to determine the thrust washer sizes needed when you can't do that until oil pressure is up? I think the instructions say to crank the engine for 30 seconds before using the tool to measure the required thrust washer thicknesses but that assumes the engine has been running recently. What is the procedure for checking thrust washer thickness on a new rebuilt engine that has never been run?

Here is a thought, the compensator takes up the slack in the valve train when the valve is completely shut. At this point there is no load on the system other than that which the internal spring in the compensator exerts on the rocker arm. Assuming that the compensator spring can take out the slack in the system then this is the position it will always be in regardless of whether or not there is oil in the system. So check to see if your compensators/system fall within the line on the measurement tool and select the pucks that achieve this if any don't.

The oil pressure is really only needed to hold the compensator in place when the force is exerted on it by the cam lobe opening the valve.

What do you think if this supposition?

 

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1983 380 SL
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Discussion Starter #1,042
Here is a thought, the compensator takes up the slack in the valve train when the valve is completely shut. At this point there is no load on the system other than that which the internal spring in the compensator exerts on the rocker arm. Assuming that the compensator spring can take out the slack in the system then this is the position it will always be in regardless of whether or not there is oil in the system. So check to see if your compensators/system fall within the line on the measurement tool and select the pucks that achieve this if any don't.

The oil pressure is really only needed to hold the compensator in place when the force is exerted on it by the cam lobe opening the valve.

What do you think if this supposition?

Not a bad supposition but for the fact that Mercedes specifically states in the instructions for setting pre-load, that you need to crank the engine over for 30 seconds before performing the test.
Also... the older pre-load test gauges were calibrated for less preload... in later years (I forget when the switch occurred but it was early 80's) the test gauges were updated to set higher preloads. The instruction manual states to make sure you are using the updated preload test gauge.
 

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1979 450SL UK spec
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Perhaps this is just to ensure that any stiction is overcome. I don't remember seeing a reference to old or new tool in the 450 manual, perhaps that's just relevant for the new engines.

Well I guess you will just have to go with your old pucks, put the head covers on, fill it with oil and turn it over with a battery and starter motor, then double check. I will do this before putting the engine back in.

I do wonder how long it will actually take to expel all the air from the compensator oil ways in the head though. The piston is a very close fit and compresses the air inside when pushed in to the body.

PS I have two additional shims made from a Stanley blade shaped into round disc.
 

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1983 380 SL
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3,729 Posts
Discussion Starter #1,045
Jyuma, did you get your exhaust manifolds ceramic coated in the end?
No, the company didn't respond to my request for a quote so I dropped it. Weeks later the company contacted me and asked if I was still interested. I didn't respond because, quite frankly, I am not sure that it's worth the effort.
 

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1979 450SL UK spec
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Possibly a dumb question.... they advise using RTV sealant on the front cover (timing chain cover) but 8 of the bolts that hold the timing chain cover, pass through the water pump, then the timing chain cover on their way to the block. If I don't put bolts in those 8 holes and tighten them, then the entire top of the timing chain cover will not get sealed tight against the block while the RTV cures.


Red arrows are where the 8 water pump bolts go through the timing chain cover and into the block.
My concern is... if I don't put bolts in those holes and tighten them down, then the RTV under them will harden in an uncompressed state. There are 4 "O" rings (two small holes top left of gray area and 2 large holes at the bottom of the gray area) that create a water passage seal between the timing chain cover and the block, these may not seal properly if they are not tightened before the RTV hardens.

The alternative is to put the water pump on at the same time that I put the timing chain cover on but that involves putting RTV on the cover and then on both sides of the water pump gasket at the same time. I had enough trouble getting it all lined up and properly RTV'd with just the cover... doing both at the same time will be problematic at best. Keep in mind that the chain must stay in place with a specific orientation or you will not be able to get the cover to seat against the block properly. I'll post a picture and an explanation of the required chain orientation later today.

View attachment 2645568
Hi Jyuma, I was surprised to see that the manual recommends a sealant, there did not seem to be any on there when I removed the timing cover.

Any thoughts on using Aviation Permatex "Form a gasket"?
 

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1979 450SL UK spec
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Removing the old gasket from the oil pan is turning out to be quite a job. I have already applied gasket remover 5 times and still there remains some stubborn gasket material that just won't come off. I don't know what kind of gasket sealer they used 36 years ago but it is mighty tough to remove.

Once I get the old gasket completely off... and I will... should I use RTV on the new gasket?

Hi Jyuma, what did you use in the end to get the gasket off, mine has turned into igneous rock!
 

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1983 380 SL
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3,729 Posts
Discussion Starter #1,048
Hi Jyuma, what did you use in the end to get the gasket off, mine has turned into igneous rock!
Igneous rock... LOL!!!

I used multiple applications of gasket remover which didn't work worth a crap... then I used a paint scraper (which worked pretty good but be careful... then I used a razor, be extra careful... and finished it off with a die grinder spinning a round Scotch Bright pad, be very very very careful. It took me a couple of days but I did manage to remove all remnants of the old igneous rock. :)

I used a very thin coat of black RTV on both sides of the gasket before I placed it on the block. I wanted a very thin layer of RTV so I put the gasket on a large piece of cardboard and spread RTV on both sides with my finger. I did little more than make the gasket wet with RTV, no bead at all. Once I put oil in the engine and get it running I'll be very happy if it doesn't leak.

Dose your engine have a rear cover like my 380 does? My manual called for a special sealer Hylomar non-setting gasket joining compound (greenish/blue color) to be used on the mating surfaces, I'm just wondering if yours does too.
MercRearCover.jpg
 

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A question for all you guys who know a great deal more about these engines then I do...

With everything in place, all the followers installed, the chain tensioner installed, and the cam timing set as close as I can get it; as I rotate the crank and the passenger side cam approaches about 30 degrees before the timing mark... the passenger side cam snaps forward and the chain becomes slack between the passenger side and the drivers side.

The slack quickly disappears as I continue to rotate the crank but it is unsettling to see that slack appear and then tighten again. I can't see that as being a positive thing to happen.
Perhaps once the engine is running, the natural rotation of the cam sprocket at idle will be faster than the snap forward and it won't be an issue... I just don't know and I'm hoping one of you do.

bTw... the reason it happens at that spot in the rotation is because two valves on the passenger side are closing almost simultaneously and the combined valve spring pressure is causing the cam to rotate rather than the sprocket rotation causing the cam to rotate. The valves that are closing when the snap forward occurs are the #1 intake and the #4 exhaust.

I saw this phenomenon yesterday and got a bit concerned, till I vaguely remembered you post on it. Seemed to get better with the tensioner fitted.
 

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1983 380 SL
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Discussion Starter #1,051
I saw this phenomenon yesterday and got a bit concerned, till I vaguely remembered you post on it. Seemed to get better with the tensioner fitted.
Yes, with the tensioner fully up to pressure with oil, the snap forward and resultant slack can't happen. :)
 
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