Author Topic: 6.9 valve springs - progressive or not?  (Read 362 times)

raueda1

  • Vintage
  • ***
  • Posts: 543
  • W116 Enthusiast
  • Location: Salt Lake City, Utah
6.9 valve springs - progressive or not?
« on: 15 April 2020, 10:33 AM »
Unit No. 923 is slowly coming back together.  Today's program is reassembling the heads.  The manual clearly states, "ATTENTION!  Mount valve springs in such a manner that the close coils are seated against rotocap."  OK, this is well known for progressive springs.  However, for the life of me, I can't see any difference in coil spacing.  So, when disassembling I didn't pay attention to orientation.  Now I'm having second thoughts.  So:

How subtle is coil spacing in progressive springs?  Enough to be immediately obvious?  Or, if it isn't obvious, then it means the springs aren't progressive? 

FWIW, in Jeff Tucker's astounding and meticulously photographed rebuild valve springs seem to be installed randomly, i.e., painted ends on top and bottom.  https://jeffreytucker.smugmug.com/1979-Mercedes-Benz-69/n-CLzLqk/

Comments welcome and thanks as always.  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Randys01

  • Classic
  • **
  • Posts: 198
  • W116 Enthusiast
  • Location: adelaide australia
Re: 6.9 valve springs - progressive or not?
« Reply #1 on: 16 April 2020, 12:12 AM »
I had my heads outsourced so the issue never came up assuming the top engine shop in town knew what they  were doing.! I agree that the springs as wound aren't that obvious. I don't recall any useful markings depicting this side up or down.
I'm sure you will get plenty of advice on line but to be double sure take a spring to  a cylingder head shop of some repute and ask them.

raueda1

  • Vintage
  • ***
  • Posts: 543
  • W116 Enthusiast
  • Location: Salt Lake City, Utah
Re: 6.9 valve springs - progressive or not?
« Reply #2 on: 16 April 2020, 08:52 AM »
I had my heads outsourced so the issue never came up assuming the top engine shop in town knew what they  were doing.! I agree that the springs as wound aren't that obvious. I don't recall any useful markings depicting this side up or down.
I'm sure you will get plenty of advice on line but to be double sure take a spring to  a cylinder head shop of some repute and ask them.
Not too much advice I'm afraid, but I think I solved my problem.  My understanding of a progressive spring was along the lines of the top picture, so I figured that the difference would be pretty obvious. Wrong!  After measuring distance between coils it became clear that these springs are progressive, but barely.   It's really only visible when the spring is viewed from the side at exactly the right angle.  See lower pic.  Otherwise you'd never see it. All the examples I looked at (n=3) had the color dots at the tight end. Anyway, problem solved.  But this certaionly won't be the last. ???  Cheers,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

  • W116 Addict
  • ****
  • Posts: 1,952
  • W116 Enthusiast
  • Location: Vancouver, BC, Canada
Re: 6.9 valve springs - progressive or not?
« Reply #3 on: 16 April 2020, 10:03 AM »
Is this maybe just another case of German-ness?  I do love these cars dearly but at times I have to shake my head at how over - engineered they are...
Daniel
1977 450 SEL 6.9 - Astralsilber

raueda1

  • Vintage
  • ***
  • Posts: 543
  • W116 Enthusiast
  • Location: Salt Lake City, Utah
Re: 6.9 valve springs - progressive or not?
« Reply #4 on: 16 April 2020, 12:02 PM »
Is this maybe just another case of German-ness?  I do love these cars dearly but at times I have to shake my head at how over - engineered they are...
I don't think so, though maybe that was the case back then.  Progressive springs are pretty standard in the hot rod engine building world.  Or even conical springs!  I'm just surprised that it's so minimal.
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

Randys01

  • Classic
  • **
  • Posts: 198
  • W116 Enthusiast
  • Location: adelaide australia
Re: 6.9 valve springs - progressive or not?
« Reply #5 on: 16 April 2020, 04:36 PM »
Those photos clearly demonstrate the variance....gotta be happy with that.

TJ 450

  • W116 Addict
  • ****
  • Posts: 4,255
  • Location: Rockingham, Western Australia
    • Tim's Insulators Downunder
Re: 6.9 valve springs - progressive or not?
« Reply #6 on: 16 April 2020, 08:19 PM »
This is interesting! Given the subtle difference, I would imagine this would go unnoticed by most rebuilders if they are not following the service manual.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

3l33ter

  • Enthusiast
  • *
  • Posts: 92
  • W116 Enthusiast
  • Location: San Francisco bay area
Re: 6.9 valve springs - progressive or not?
« Reply #7 on: 02 May 2020, 12:35 AM »
I'm putting mine back together after changing the head gaskets. I had a machinist work on the heads for me and I doubt he put the springs back correctly - I myself just learned this right now!

I'll check my valve springs tomorrow. Can one tell the difference in coil spacing when they're already installed?
'75 280S
'77 6.9
'82 300TD

raueda1

  • Vintage
  • ***
  • Posts: 543
  • W116 Enthusiast
  • Location: Salt Lake City, Utah
Re: 6.9 valve springs - progressive or not?
« Reply #8 on: 02 May 2020, 07:53 AM »
I'm putting mine back together after changing the head gaskets. I had a machinist work on the heads for me and I doubt he put the springs back correctly - I myself just learned this right now!

I'll check my valve springs tomorrow. Can one tell the difference in coil spacing when they're already installed?
I very greatly doubt it.  You can hardly tell when they're out, and then only when oriented perfectly as per the pix.  That said, I noted that the paint marks were uniformly on the bottom.  This was the case on 2 6.9's.  Good luck!
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

3l33ter

  • Enthusiast
  • *
  • Posts: 92
  • W116 Enthusiast
  • Location: San Francisco bay area
Re: 6.9 valve springs - progressive or not?
« Reply #9 on: 24 June 2020, 09:37 PM »
I borrowed a valve spring compressor and took out a spring. With it out, you can just barely tell that the outer springs are progressive.

The wire is 4.8mm thick at the bottom and 4.7mm thick at the top. Coil spacing is 4.8mm at the bottom, 5mm at the top. This was just my spring - no idea if it's worn out, etc.

The inner spring isn't progressive as far as I can see/measure.

The one I took out was upside down, so I proceeded to take them all out and flip the ones that needed flipping!

Word to the wise: the exhaust valves are non-magnetic, so a magnet won't grab them.
'75 280S
'77 6.9
'82 300TD