My 83 300DT's been very sluggish lately. I just adjusted the valves and what a difference! Regained lost pep and a smoother idle. Valves were all tight! .002 and .011 for in/exh when it should be .004 and .014. I made an extension wire pair of 6 gauge wire to the plastic box on the passenger wheel well and used in to bump the starter to line up each valve to point upwards before setting the clearance and had very good control. When I finished the valves, I cleaned the timing marks on the harmonic balancer with 600 grit wet/dry paper wrappsed to the end of a long wooden dowel secured with a rubber band and with a little bit of Zep purple cleaner, cleaned off the grime so the timing marking are legible. I used the bump starter and slowly advanced the engine till the 2 marks on the cam sprocket are lined up. Hit it right on the first try can't believe it. With the cam marks lined up the harmonic balancer marks are 2 degrees after the zero mark which is located just after the RPM sensor tooth. Is that 2 degree after TDC? And is that acceptable chain stretch and is using the starter motor to advance the engine valid or should I have turned the crankahsft with a socket by hand? The pic on the Haynes manual says it should be at zero on the harmonic balancer when the cam marks are aligned.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Do you have a picture of the alignment? Those marks on the tower and cam have to be "perfectly" lined up or it will be off by quite a bit down on the balancer.

There is some information on this in the resources section at the top of the page (under DIY articles). It has been a while since I looked at it. Could be the Dial indicator method (valve lift). I cannot remember.

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AJ

1985 300D (SOLD)

The mark on the cam tower was perfectly aligned to the mark on the sprocket. Like I said earlier, I couldn't believe that I hit it the first time round. Unfortunately I did not take a pic. of the cam marks. I did take one of the marks on the harmonic balancer with my cell camera but I'm not sure how well the marks can be seen, if at all. I post the pic anyway in a little bit.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yeah, the cam mark alignment is ultra critical must be absolutely dead center. amazing you could hit that with the starter! I'd try it again, and get it close with the starter then use the PS nut or the crank nut to nudge it to the absolute dead center again. you must get your head right in line with the side of the cam and the mark on the tower to see it properl y aligned, and have the mark exactly centered in between the two marks on the tower.
all that said, 2degrees LATE is not bad at all!

I'm driving around and don't think I will pull the valve cover to do it again. I'm 100% positive the marks were aligned. I was looking at them (my eye balls were 6" away from the marks) as I touch the 2 fat wires together to bump the starter and they lined up perfectly in the 2nd bump.

I bought it used with a broken odometer at 240K. Who knows how long it's been broken with the PO? It's at 273K now and it could have well over 300k on it. Can an original timing chain with over 300k have this little stretch?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I can't tell on my phone whether the timing marks are legible in this pic. Is it?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Looking at the pic above on the computer now. Can't make out the numbers on the harmonic balancer but you can see the round rpm sensor tooth to the right of the pointer. The tooth is just before zero degree TDC.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

don't forget that an offset key could have been put in. and you have no reliable way to know if the chain was replaced or not do you?
300K is approaching the limit a chain under normal service intervals would be within the stretch limits.

Can an offeset key be discerned without taking the sprocket out?
I have no idea if the chain was ever replaced by PO's. My hunch is no.
I'm still amazed at how much better the car runs with the valve adjustment. If I can get the transmission shift points set right, it'd be a real sweet ride. And I know what "right" feels like. I drove Tyler's Ol Turbo when I drove out there last year to look at a car he was selling and had a chance to drive it. That car was sweet and shifted crisply and smoothly, no lurch whatsoever.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

You might be able to tell if the keyway on the cam is dead center aligned with the keyway on the shaft.
Obviously the bestway to tell is to take the cam sprocket off and look at the key itself.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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