I am getting prepared to overhaul my 350k old engine sometime next week and I already started to obtain parts and got an appointment from the machine shop. Any suggestions and help is much appreciated as I am trying to build an nearly perfect engine.

- I will replace the valves with original spares, do I also need to change guides and springs?

- I am thinking of machining the cylinder head in order to increase the compression ratio. What are the pros and cons, assuming everything is calculated and done right? (mechanical engineer here)

- I obtained mahle pistons with +0.5mm diameter. In order to insure longest engine life and less compression leak, what is the optimum honing value recommended for the cylinders? I will make sure the engine is treated carefully during the break in period anyways so I want to go as tight as I can.

- How exactly are pistons and rods blueprinted? Do you recommend material removal in order to make all parts weigh same?

- What is your recommendation for the crankshaft?

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2001 E200 Kompressor Avantgarde
1987 300E 5-speed
1976 450SLC
1975 280S (sold)
1973 230.6 (sold)

- I will replace the valves with original spares, do I also need to change guides and springs?

Yes on the guides.
If the springs are in spec I would re-use them.

- I am thinking of machining the cylinder head in order to increase the compression ratio. What are the pros and cons, assuming everything is calculated and done right? (mechanical engineer here)

Recommend against because of the tolerances between the moving parts of the block/head. You got 300k+ out of what you have - why not stick with it? (mechanical engineer here)

- I obtained mahle pistons with +0.05mm diameter. In order to insure longest engine life and less compression leak, what is the optimum honing value recommended for the cylinders? I will make sure the engine is treated carefully during the break in period anyways so I want to go as tight as I can.

I would follow the specs in the manual on this one.

- How exactly are pistons and rods blueprinted? Do you recommend material removal in order to make all parts weigh same?

I recommend against material removal unless you are building a race car.

- What is your recommendation for the crankshaft?

Let the machine shop inspect the crank. Best case all they will do is polish it. Worst case they will have to turn it some and install oversize brgs.
good luck

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Jim

MB engines are from the factory exceed most "chevy blueprinted" specs.

Everything is balanced to higher standards. Go with the factory manual and make sure your machine shop is does MB work. IF they bore for clearance the way most do american V8- you won't hit the factory wear limits.
Valve guides need to be final reamed to the correct size... again most machine shops are not setup to do benz work.

If you've kept up with oil changes- doubt the crank will need grinding. Lower ends are strong..

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

Unless you have excessive blowby, chances are all you need is the valve job -- remove head and inspect cylinder walls. If you can still see the factory honing marks, leave it alone. My M103 has 220,000 miles (not kilometers) on it, and is still fine. Valve job at 160,000 miles. Very likely you will not be able to detect wear in the bores.

Valve guides are shot, replace as a matter of course. Springs will need to be measured -- if any are below height specification, replace them all. Replace all the lifters and inspect the rocker arms -- if any are dubious, replace the lot.

Cylinder bore to piston clearance is quite tight on these engines (0.001", don't know the metric spec off the top of my head). You will not need to balance the pistons or rods, it's done already. Mahle pistons will be well within the tolerance of 5 gr difference anyway.

Unless you've run it out of oil, the crank will be fine, probably won't even need polishing. Oil clearance on the bearings should be on the small end of the tolerance for longest life.

Valve to guide clearance should be nearly zero -- MB guides and valves are very straight, so if the oiled valve will go into the guide and the spring will return it to the closed position, clearance is correct. Do not, under any circumstances, provide more than 0.0005" clearance between new guide and vlave, it will shortly start burning oil.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

i appreciate your tips, the project will begin within few days and my parts are complete now. machine shop is specialized in german manufacturers and they have recently upgraded their machinery with brand new ones, even a cnc is available for cad/cam cylinder head works. i will use mineral oil for the first 3-5k then switch to synthetic oil.

__________________
2001 E200 Kompressor Avantgarde
1987 300E 5-speed
1976 450SLC
1975 280S (sold)
1973 230.6 (sold)