Engine - Valve Guide Repair

GROUP 11
Engine



Bulletin Number
11 11 86 (1320)



Montvale, NJ
April 1988
Technical Dept.



This Service Information Bulletin supersedes SI 11 11 86 (1320) dated August 1987. It announces the valve stem/guide radial play limit for the M70 engine.


Please remove and discard S1 11 11 86 (1320) dated August 1987 from your SI binder.


SUBJECT:
Worn Valve Guide Repair


ENGINES:
All


Situation:
As previously announced, valve guides will no longer be replaced as a remedy for excessive valve stem/guide clearance. Instead, the valve guide's inside diameter will be reamed to one of two available oversizes ( + 0.1 mm or + 0.2 mm). A valve with a corresponding oversize stem is then fitted to the guide, thus the valve stem/guide running clearance is restored to "new" specifications.



Checking
Procedure:
1) With the cylinder head dismantled and clean, mount dial indicator (88 88 6 002 510) with the clamping tool (88 88 6 002 500).

2) Measure the present valve stem diameter and insert a new valve of the same diameter into the valve guide to be checked.

3) Lift valve from valve seat until the end of the stem is flush with the collar of the valve guide.



4) Check the radial play using the dial indicator. Should the radial play exceed the *specified limit, ream the valve guide to the next applicable oversize.


Valve stem/guide radial play limit (tilt clearance "K")

Engine M70

Intake 0.50 mm

Exhaust 0.50 mm


*All other valve stem/guide clearance limits (tilt clearance "K") can be found in the current Technical Data Fiche.

5) Repeat the procedure for each valve guide.


Reaming
Procedure:
^ Select the next applicable oversize reamer (7.1 or 7.2 mm for S14, S38, M20, M21, M70 engines and 8.1 mm or 8.2 mm for M10, M30 engines)

^ Valve guides must be reamed from the combustion chamber side.

^ Only turn the reamer in the clockwise direction when inserting or withdrawing it from the guide.

^ Use a cutting oil.

^ When reaming, press the guide cone onto the valve seat insert.

^ After reaming about half the length, withdraw the reamer (continue to turn clockwise) and remove any chips.

^ Use a tee handle when turning the reamer to ensure a concentric cutting motion.

Note:
After the valve guides have been reamed, it is necessary to refinish the valve seats in the cylinder head.

USE APPROVED VALVE SEAT REFACING TOOL 88 88 6 003 580.

Parts/Repair
Information:
Part numbers of valves with oversize stems are indicated in the corresponding parts microfiche.

Standard valve stem seals are to be used on valves with oversized stems.

Labor
Allowance:
2 Flat Rate Units are required for the reaming of one valve guide.