Top end rebuild & loss of compression

[gfa230sl]

Hello,
 I have a 1966 230sl w/German specs. and a 127 engine. My father and I got it running again a few years ago. It was running well for 2 years then a few months ago it was having some issues (difficulty starting, exhaust backfire at air intake) running and I suspected the head gasket. I removed the head and found a crack in the gasket between the 3 and 4 cylinder. Also, coolant had been getting in cylinder 3. I took the valves out and cleaned them up. They looked pretty good, so I put them back with new valve seals. I cleaned up the head and everything looks flat and square. I replaced the head and exhaust manifold gaskets and put it back together replacing hoses, gaskets, and other minor things along the way. I followed the torque guide for the head per the manual. After getting it back together I do not have much compression at all. I made sure to align the camshaft notch while the engine was TDC and the mark on the harmonic balancer was at 0. Note: there are two sets of markings on the balancer. I read in the forum that they used the balancer on more than one engine, so the marks I am to use depends on the shape of the indicator I have. I took the FIP off as well, so I checked the alignment on it 20 above TDC. The engine turns over but sounds weak. I cannot get a reading on the compression gauge, but I can feel air coming out of the plug holes when it spins over. I verified I get a spark and fuel out at each injector. This tells me it is most likely a compression issue. I am near the point of pulling the head again and adding some copper gasket spray to see if that helps seal things up. I also thought it could still be an alignment or timing issue between the pistons and the valves. Any thoughts, suggestions, comments are welcome.
 Regards,
  Neil

[ja17]

Take a compression check. Make sure that when no one piston is at TDC your pointer is on "0" and the slot on the camshaft washer is aligned with the mark on the front cam support.

[Pinder]

Check the valve cleareances are set to spec.  I had on my engine had them set to tight and they were not closing properly and I had no compression until I set it to specs.

[gfa230sl]

JA17,
    I did was very carful to follow that order.  The only issue was the two different scales on the harmonic balancer. I think I followed the correct one, the scale nearest the front of the engine. I did that because my pointer is an arrow shape and not a triangle shape.
Thanks,
Neil

[gfa230sl]

Pinder,
   I will check the valve clearance as soon as I can. I'll report back.
Thanks,
Neil

[ja17]

The triangle pointer uses the rear scale. The older rectangular pointer uses the front scale closest to the radiator.

[David Robinson]

It might be worth getting the head checked for out-of-flat just in case it needs a skim.

[gfa230sl]

Thank you all for the help. I finally had time to get back to working on the car after a very busy summer. The lack of compression was caused by the valve adjustment as Pinder suggested. I adjusted the valve clearances to spec, and it cranked up. I still think I have a timing issue as it runs rough.  I am going to re-time the Cam, crank and IP as described here by ja17: https://www.sl113.org/forums/index.php?topic=14791.msg101189#msg101189. I'll update again as soon as I can and try not to wait 4 months to get back at it again.

Thanks again everyone,
Neil

[gfa230sl]

I re-synced the cam, crank shafts and the Distro and fuel pump. It runs better but still runs rough and severely under powered. I'm not sure what's wrong at this point. I had to move both the distro and fuel pump 180 degrees to get it all in line. Could dwell angle or Distro alignment have a large effect on power? I will need to get a timing light to dial it in.

[Cees Klumper]

Definitely set the ignition timing according to specifications with a timing light. Timing has a significant effect on the engine's performance.

[gfa230sl]

Thanks Cees,
   I reset the point dwell and timing, and all appears to be well! I drove the car for 5 or so miles and was able to get up to 55 mph without issue. I think I finally have my baby back up and running again.
Thx,
Neil