OM617 (non turbo) cam profile specs, piston height specs etc - PeachParts Mercedes-Benz Forum

vstech · #1 01-22-2011, 09:06 AM

ok

Stretch · #2 01-22-2011, 09:13 AM

Quote:

Originally Posted by vstech

ok

Thanks for the thread rename John - it explains a bit more about the content now!

Stretch · #3 02-09-2011, 04:59 AM

Here is data for the position of the cam lobes.

I've only got a 150mm vernier caliper so they are not as good as they could be - there is an accumulative error in the summation of the individual distances for the new cam shaft - the old one I've got worked out better - that was pure luck!

Stretch · #4 11-27-2011, 02:48 PM

...that I'd like to correct.

In post 20 I've got the clearance wrong.

The clearance was measured directly as described in the post.

I measured the "drop" of the valve from its position in the valve seat to the piston crown. This was:-

Inlet (cylinder #1) 3.18mm
Exhaust (cylinder #1) 2.88mm

This is the clearance.

I was trying to find out how thick the head gasket was when fitted... I'm interested in this because the piston on my engine sticks out above the surface of the block by 0.85mm. The head gasket is the only thing that stops disaster!

This roughly drawn picture above is meant to show that the valves are recessed into the head.

In my engine they were:-

Inlet (cylinder #1) 1.05 mm
Exhaust (cylinder #1) 0.8 mm

The recess in the piston crown was measured to be 1.25mm

So adding the distance of the recess in the crown of the piston to the depth at which the valves have been recessed into the head you get

Inlet (cylinder #1) 1.05 mm + 1.25mm = 2.3 mm
Exhaust (cylinder #1) 0.8 mm + 1.25mm = 2.05 mm

So subtracting the combined values of the recesses the distance between the top of the piston and the head is either

Inlet (cylinder #1) 3.18 mm - 2.3 mm = 0.88mm

or

Exhaust (cylinder #1) 2.88 mm - 2.05 mm = 0.83mm

As said before 0.05mm has been "lost" some where in the measuring process. This is equal to the precision of my depth gauge...

So after all that I can estimate my head gasket thickness when fitted to be somewhere between 1.68 mm and 1.73mm on a cold engine! The uncompressed head gasket thickness was 2.2mm.

So a head gasket seems to be compressed by about 20% of its thickness when fitted.

Stretch · #5 11-28-2011, 05:45 AM

I've been wondering about the odd numbers of offset correction for timing chain elongation described in the FSM (chap 5-215). I've done some calculations that suggest that the smallest offset key is pretty useless...

Well it is pretty useless to correct for 4 degrees - it is better for 6!

Take a look at this image of the PDF I've attached.

The diameter of the hole in the camshaft sprocket on my OM617 non turbo is most definitely 28mm - but it looks like Mercedes have designed the offset keys for a 30mm diameter. Does anyone know if the turbo cam has a 30mm diameter hole in the camshaft sprocket?

And the size of the Woodruff key / offset key slot is 4mm

I've measured the PCD of the camshaft sprocket and I reckon it is 119mm. I've used this value to calculate the circumference of a "circle" running around the sprocket where I expect the chain to be resting. This circumference was then proportionally divided up for each angle of elongation => i.e. circumference of PCD circle divided by 360 degrees multiplied by "degree of elongation at camshaft sprocket"

It is nice to see that roughly speaking if you have one degree of elongation measured at the crank that is equivalent to about 0.5mm linear elongation.

Stretch · #6 11-28-2011, 03:12 PM

...the difference between the calculations and the data in the FSM?