Author Topic: Questions about valve adjustment on a 1980 300SD  (Read 156 times)

avantbenz

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Questions about valve adjustment on a 1980 300SD
« on: 10 July 2019, 10:43 AM »
I’m not sure the make model is that relevant here - this is more of a procedural inquiry.

I’m having difficulty “unlocking” the locking nut in order to utilize the adjusting nut. I’m assuming standard lefty loose-y applies here while holding the top adjustment but steady with the wrench but I’m not sure how much torque to apply to break the lock nut free. I don’t want to damage anything.

I made a short video. Please excuse my blather - it’s sometimes hard to get these points across succinctly with a wrench in my hand.

https://youtu.be/f6FuWlbB0G4
Daily Driving 'Patience' ~ 1980 300SD

Squiggle Dog

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Re: Questions about valve adjustment on a 1980 300SD
« Reply #1 on: 10 July 2019, 11:03 PM »
I've done this a few times on my 300SD, and it appears you are applying force to the wrong side of each nut. What you want to do is reverse the direction of the wrenches so you turn the nuts away from each other. The threads are lefty loosey, righty tightey. Think of it like a jam nuts like you'd see on top of a shock absorber. You want to turn the upper nut counter-clockwise while turning the lower nut clockwise so they loosen up.

The way you are holding the wrenches is good, but just move the lower wrench onto the upper nut, and vice versa. It can take quite a bit of force to break them free. You probably won't break anything, but make sure you don't slip and round off a nut, as there is a real danger of that.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
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Diesel 617

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Re: Questions about valve adjustment on a 1980 300SD
« Reply #2 on: 11 July 2019, 09:13 AM »
You can use high force when tightening and loosening. For the most part my readings only change .01mm on average when I adjust my valves.

Squiggle Dog is spot on, It will take some practice to get the feel right, one wrench on top and one wrench on bottom, brace with the bottom wrench and loose the top nut. Then loosen bottom nut slightly and tighten top nut with feeler gauges in-between valves and cam lobes tighten with feeler gauges still in-between. When you are done tightening you should be able to with draw the feeler gauges without force and be unable to get the next higher and lower size in-between the lobes and the valves. Play around with the first valve until you understand fully how to tighten and loosen.

Use a cut out to remember which valves and exhaust and which are intake. Ive made the mistake before.

This thread might help too: https://www.peachparts.com/shopforum/diesel-discussion/107729-valve-adjustment-om615-616-617-fyi.html

How to hold wrenches: http://www.startekinfo.de/etools/content/tool.jsp?toolno=615%20589%2000%2003%2000
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avantbenz

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Re: Questions about valve adjustment on a 1980 300SD
« Reply #3 on: 11 July 2019, 10:55 AM »
Thanks Squiggle Dog and Diesel Giant 617 - I'm going to give it another try today.

Diesel 617, in the diagram you posted it looks like that cam is in the 1 o'clock position (as opposed to straight up). That was something else that confused me - when to adjust the valves. Both Diesel Giant and Uncle Ken say when the lobe is "straight up" but does that mean the top most point straight up, or the one smooth flat side in a vertical position? And if the latter, on which side - the passenger side, or the driver's side? I'm not in front of the car to take pictures, unfortunately.

Basically, the diagram reflects the cam as straight up from the rocker arm that is at an angle from the valve stem - what is correct?
« Last Edit: 11 July 2019, 11:07 AM by avantbenz »
Daily Driving 'Patience' ~ 1980 300SD

Squiggle Dog

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Re: Questions about valve adjustment on a 1980 300SD
« Reply #4 on: 11 July 2019, 11:05 AM »
I like to do mine with the cam lobe pointing 180 degrees from the rocker arm (1:00 position). However, doing it with the cam lobe pointing straight up should work, too, as there isn't a change in the diameter of the cam lobe until well past this point.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Heated Seats, 347,000+