280SL head removal lessons learned and advice please.

[wray]

By way of background I am removing the cylinder head on my wife's 1970 280SL. 4 speed. I have completed various ground up restorations on English sports cars. I purchased a Haynes manual recently and it is a decent but not excellent guide to this job. The car smokes bright blue after idle at a stop light, my hope is that the valve stem steals and or guides need replacement. If the original owner, whom I purchased the car from,  did not misrepresent the mileage, the car has about 60,000 miles. Replacement unnumbered engine block. what I have learned so far;

1.) valve cover easily removed if the rear most is lifted up first, clearing the hood latch mechanism.
2.)  I should have put the car on my lift before I started this process as I find I have needed quite a bit of access to the bottom of the car.
3.) once the injection lines are removed, cover the fuel pump inlets with tape or covering of your choice to keep any dirt out of the pump. same for fuel line source to intake manifold.
4.) It is likely the exhaust system, a  replacement stainless affair, may have to be completely dropped to free up the exhaust manifolds, particularly the section nearest the radiator.
5.) Removing the thermostat housing requires much patience as it slides off the studs, which are quite long.
6.) Freeing up the power steering reservoir is a nasty job, the bracket mounts to both the fuel injection pump housing bolt and a bolt into the distributor base. I found that if both are loosened enough the PS reservoir can be pushed away to clear the head.
7.) My retired mechanic advised that I safety wire the cam sprocket to the timing chain it would keep it the assembly in place once  the timing chain sprocket is  removed from the cam.
8.)I wedged a very sturdy tire iron  into a hole on the timing chain sprocket and wedged it against the cam tower, then very gradually pulled the sprocket bolt loose to maintain a top dead center position on the engine.
9.) Hard FI lines must be disconnected from front to back of top of FI pump.   

Head bolts are now loose and I am at the point of pulling the head. I will ask some friends to assist as I simply don't want to "drop" the wired up sprocket timing chain assembly into the head opening for fear of the chain coming loose from the crank sprocket. I would appreciate any strategies from the forum on this last issue. What has helped you in keeping the timing chain position intact as the head is lifted from the block?

 

   


   

[Shvegel]

As long as you don’t drop the chain in the engine you should be fine. I usually attach a long piece of safety wire so even if it does drop I still stand a chance of coming out OK.  Pull the head and as long as you have helpers have someone just keep tension on the chain while you pull the head off.  It generally doesn’t cause a problem even if you drop it in so don’t get too stressed out about it.

If you have not found it yet there is a “secret bolt” hidden in the oil puddle under the tensioner.  6mm allen if memory serves.  From memory again I think there is also another allen headed bolt inside chain galley.

Your symptoms sound exactly like what my car was doing when I pulled it apart.  There is a tendency for one of the valve guides to come loose in the head and start moving with the valve.  This may be your issue.  Regardless, I strongly recommend replacing all the valve guides as the new ones are modified with a step to prevent the guides from dropping down.

Since you have English car experience I will caution you that the head should require very little effort to get off.  If you are fighting it there is still a bolt in there somewhere.  No need to hang the car from the head like a 6 cyl Jag.

[Pawel66]

If I may throw in my 2 cents (from an amateur perspective, who pays attention to things that are obvious to pros, being through a similar route as you are):
1. I used plastic loom ties (tritittits as they are called in my language because of the sound they make as you tighten them) to secure chain to sprockets and chain to chain so that it does not become lose.
2. I have read on this forum that if you have troubles removing valve cover because of the hood latch - it may indicate your rear transmission mount is worn or out of adjustment (is too low) - may want to look at it and replace it or adjust it with shims.
3. If you need, for whatever reason, to pull further away the PS fluid reservoir - it is done fairly easy when you just detach it from the bracket (just one clamp). Then removing bracket is also easy as you have access to all 3 screws. I pumped out some fluid when doing this and used opportunity to replace the filter.
4. If the engine was replaced, you may want to check if the 19mm head screw that holds the PS reservoir to the block where the distributor sprocket is has a special tip and has a proper length (I think ca 24mm from bottom of the head to the tip). If someone took the block with this screw from a car without PS, this screw will be too short now. It prevents chain from jumping teeth on the sprocket and should have the proper end and lenght.
5. If you need to remove injection lines completely - maybe it is best to do it in one piece by undoing the big screw holding the front bracket and not touch the 5 clamps on them.
6. I do not know how common is the type of tensioner that we have there, so just maybe: not to forget to prime it and punp it a bit before assembling the lot together.
7. Look at the way to fit tappets with 5mm allen key in tech Manual - huge time saver.
8. Do not tighten the valve cover bolts too much - the brackets may bend in and make noise.

All these may be obvious, then sorry.

[wray]

Thanks, does the idler sprocket need to be removed so that cam sprocket and chain tied together can be passed thru the head?

[ja17]

Note the position of the ignition distributor also. Yes, if you leave the cam sprocket wired to the timing chain you will need to remove the idler sprocket.

[wray]

many thanks for the advice, head should be off today. floating on the block now, just need a seconds set of hands to pass the timing gear thru the head. Engine is at TDC given cam and sprocket marks and position of rotor.

This forum has been very helpful.

[johnk]

I fixed a string to the ceiling above the engine and tied a bungy cord on the end to it to hold the timing chain up in the air during the process. Given that the bungy cords stretches it was easy to unhitch an re-hitch it to the timing chain while removing the head. It will hold the chain up to the side of the head while you while you are positioning it for the lift.