4.5 Valve Stem Seals How to?

[ptm]

My 1973 280sel 4.5 needs the stem seals replaced and was wondering if there are good write ups or repair manuals about it? I did a search but didn't find much.

Thanks

[97 SL320]

Did you search the Mercedes parts section of this site? They have info there also.

I'm guessing this uses a cam over rocker setup. ( Valve below one end of rocker , lash adjuster below the other end, cam above rocker in the middle )

If so, pretty much any older MB info would work for the basics. Generally the valve is compressed slightly and rocker slid out rather than removing the camshaft to gain access to the valve springs.

Even a 1973 to 2000 ish Ford 2.3 / 2.5 OHC write up would be similar.

[Tony H]

It would be a pretty major job-you would need to remove all the rockers, apply compressed air to each cylinder you are working on while locking the engine, remove the valve springs without dropping the valves into the cylinders, replace the seals and putting it all back together. Usually the valve guides are worn out on these engines-you might save yourself some work and pull the heads to check the guides and replace the seals.

[Tomguy]

I hate to be the bearer of bad news but Tony is likely right. I did the seals on my 4.5 and they had no effect on the smoking because the valve guides were shot. You might get lucky, especially if the engine is below 120k known miles with good oil changes and no gas/oil dilution, and not have a guide issue.

[joshhol]

Sorry but what do you mean by no good write ups? There are plenty of write ups on this site alone, let alone the entire www.

This link alone has all you need
Engine Mechanical:

Put forth some effort...

[ptm]

Originally Posted by joshhol

Sorry but what do you mean by no good write ups? There are plenty of write ups on this site alone, let alone the entire www.

This link alone has all you need
Engine Mechanical:

Put forth some effort...

I'm looking for something specific to the 4.5, like do the cams need to come out and valve adjustments and torque specs. The engines in the link look nothing like the 4.5.

[vandor]

Originally Posted by Tony H

...apply compressed air to each cylinder you are working on while locking the engine, ...

I tried the compressed air trick, but in my experience just a little push on it would let the valve fall anyways. So I just ended up putting the piston of the cylinder I was working on at TDC, so the valves could only drop a little.

[ptm]

Originally Posted by joshhol

Sorry but what do you mean by no good write ups? There are plenty of write ups on this site alone, let alone the entire www.

This link alone has all you need
Engine Mechanical:

Put forth some effort...

I'm looking for something specific to the 4.5. Those write ups have a completely different valve set up.

[ptm]

I'm looking for something specific to the 4.5. The 4.5 has a completely different valve set up then in the link write ups.

[fonzi]

I have nearly the same car (1973 280se 4.5). Same issue here. Old separated oil (lumpy on bottom plus thin) was in my car and an oil change for some thick 20w/50 oil seemed to just make the smoking more consistent with big plumes of oil smoke when I hit the gas pedal. It gives a pretty consistent smoke idling too, but could almost be mistaken for normal sometimes.

I really want(ed) to do the valve stem seals on mine since they are so cheap. I'd hate to waste the time and get no results. But I got an estimate of something like $3500-6000 to rebuild the heads. I've got other engines I'd be tempted to swap in first. But... valve stem seals do sound easier. Worth a shot?

[joshhol]

Same concept. Valve trains aren't that different.