The BMW manual gives a valve spring lenght (not compressed position) to check when rebuilding a cylinder heads.
My R50 springs are (after 40 years):
outer - 1 mm less than nominal
inner - 2,5 mm less than nominal
Is it really necessary to change them?
which is the allowable tolerance in this case ?
What could happen if I do not change them?
Thanks
Michele
Valve spring lenght
-
Thorsten Franz
Re: Valve spring lenght
Hi Michele,
Can't resist to share my limited knowledge with you. Over the years of use the valve springs loose load/suspension resulting into reduced accuracy of the valve opening/closing process and sealing effect of the closed valve. This will lead to a considerable loss of performance depending on actual wear of the springs. It would be a waste of money to replace/restore everything else while neglecting the rather inexpensive valve springs . -'could not find anything about permissable tolerances. Even a used spring which still has the nominal length might already have reduced load.
Ask your machine shop to measure the load
with springs at compressed length. You will find the nominal values in the workshop manual.
When I compared the old valves of my R26 and R50/2 with the new ones I could even feel the difference by pressing them between thump and fingers.
Have fun
& best regards
Thorsten
Can't resist to share my limited knowledge with you. Over the years of use the valve springs loose load/suspension resulting into reduced accuracy of the valve opening/closing process and sealing effect of the closed valve. This will lead to a considerable loss of performance depending on actual wear of the springs. It would be a waste of money to replace/restore everything else while neglecting the rather inexpensive valve springs . -'could not find anything about permissable tolerances. Even a used spring which still has the nominal length might already have reduced load.
Ask your machine shop to measure the load
with springs at compressed length. You will find the nominal values in the workshop manual.
When I compared the old valves of my R26 and R50/2 with the new ones I could even feel the difference by pressing them between thump and fingers.
Have fun
& best regards
Thorsten