Valve adjustment

[OldMercs]

About to reinstall the cylinder heads on my '73 450sel, to adjust the valve clearance is it necessary to loosen the big "bushing" nut before turning the 17mm ball stud? I've viewed the service manual and it would imply that the 17mm ball stud can be turned without having to loosen anything else, seems rather tight to me but I've never messed with these.

[ctaylor738]

You don't need to loosen the bushing, but be prepared to remove the rocker and put a deep-well socket on stubborn adjusters, especially if you have to make a large adjustment, which can be the case if you did the valves.

[GaryF]

Originally Posted by OldMercs

seems rather tight to me but I've never messed with these.

This is intentional to stop it adjusting itself with vibration, anything less than 15 ft-lbs required to turn it and you need to replace the threaded bushing below.

[Thomas Webb]

Oldmercs -

I just did this! And I did it with a 17mm crowfoot from Craftsman. As already mentioned, the large nut is not part of the procedure - just the nut on the ball adjuster. I had to grind down my crowfoot to fit without rubbing against the pedestals or retainer springs.

The nuts are TIGHT. There machined to an interference fit and are purposely done this way to avoid having them loosen. It's a much better affair that many push-rod cars where you have to hold the locking nut with a wrench whilst turning in (or out) the adjusting screw (MGs, Triumphs, Healeys, etc).

If your nuts are REALLY tight, you may want a third hand to make sure and avoid having your crowfoot slip off, and round off, the ball-nut adjuster - if that happens you're screwed - no pun intended.

Some of my valves were tight (not too much), but I probably saved a lot of valve problems down the road by making sure they were correct. I wasn't rebuilding as you are, just normal maintenance - something to keep in mind. Since you have a "new" engine, you will need to re-torque your heads after some mileage - which will also affect your valve adjustment (again) and you will need to readjust them after re-torquing.

[OldMercs]

Thanks for the replies. As long as I know they're supposed to be tight I can be confident I'm not destroying anything while adjusting them.

[nhdoc]

There (of course) is a special undercut offset crowsfoot socket for this job that you're supposed to use a torque wrench on while adjusting the nuts so that any that are looser than spec can be found and replaced.