Engine - Revised Head Bolts/Tightening Procedure

86BMW09

GROUP 11 Engine
Bulletin Number 11 19 85 (1106) Page 1 of 4
Montvale, NJ June 1986 Technical Dept.
This Service Information Bulletin supersedes S.I. 11 09 85 (1003) dated March 1985. It contains new tightening procedures for cylinders head bolts.

Please remove and discard S.I. 11 09 85 (1003) dated March 1985 from your S.I. binder.

SUBJECTS: I. Cylinder head bolt shoulder shortened. II. Revised tightening procedure for cylinder head bolts, valid for old and new version bolts. III. Valve clearance adjustment.

MODELS: All

I. Cylinder head bolt shoulder shortened.

Situation: Rocker arm shafts difficult to remove.

Cause: Unfavorable combination of tolerances between rocker arm shaft and cylinder head bolt shoulders, which might produce burrs on rocker arm shafts.



Correction: The bolt shoulder was shortened from 22 mm to 18 mm (see sketch) and gradually introduced into series production.
Note: Whenever cylinder head bolts have to be removed for any engine repair, check if long shouldered bolts have been used and if they show any damage at the shoulder itself. If one or more are found to be damaged, all bolts have to be replaced by the new version with a shorter shoulder. DO NOT MIX LONG AND SHORT SHOULDERED CYLINDER HEAD BOLTS ON THE SAME ENGINE!

FIGURE 1:

CAUTION: M 30 Engines If cylinder head bolts with a short shoulder are used, dowel pins 11 1 063 will have to be used in bolt bores 7, 9, 12 and 14 to hold the rocker arm shafts in position while disassembling and assembling the cylinder head (see Figure 1).

FIGURE 2:

To mount the cylinder head on the engine block, screw in all other cylinder head bolts and tighten bolts 1 through 6 in correct tightening order (see Figure 2) to the first tightening torque value. Replace dowel pins with cylinder head bolts. Now tighten bolts 7 through 14 in the correct order to the first tightening torque value.


Check order of cylinder head bolts 1 through 14 when tightening them to torque values and torque angles (see Figure 2).



II. Revised tightening procedure for cylinder head bolts.

The following procedure should be followed on all repair work where torquing of the cylinder head bolts is required. This procedure is valid for all BMW engines.
Torque angle tightening can be made after the engine warm-up running phase regardless of engine temperature. Valve clearance adjustments are not necessary after the final torque angle tightening.

a) M 21 D = BMW 524 td.
b) M 88/3 = BMW M 635 CSi/4-valve
c) Waiting time = cylinder head gasket settling time
d) Warm-up running = time to run engine to coolant temperature of 185 to 203~F (85 to 95~C)

These revised specifications are effective immediately. They eliminate the requirement for cylinder head retorquing at pre-delivery inspection and 1200 mile inspection.



III. Valve clearance adjustment. The valve clearance is the same for intake and exhaust valves:
Note: Checking and adjusting the valves is required at the 1200 mile Inspection.
Miscellaneous
Information: Cylinder Head Installation The threads of bolts and tapped bores in the engine block have to be cleaned prior to reinstallation of a cylinder head.

Check that cylinder head bolts can be screwed into the engine block by hand up to the end of threads prior to installation of the cylinder head. Please check for an increase in torque (harder turning) of bolt during this test, which could be caused by the following:

1. Damaged threads on cylinder head bolt and/or in tapped bore of engine block.

2. Oil and/or water or pieces of cylinder head gasket in tapped bore.

Corrective Measures for Point 1:
Bolt threads - Replace bolt
Threads in engine block damaged - Recut threads with size 3 tap

Corrective Measures for Point 2:
Clean tapped bores with compressed air.

We must point out again that no sealant whatsoever may be used for cylinder head repairs. The only exception is on M 10/M 30 engines, where a hole provided in the cylinder head gasket for the engine block/timing case cover connection point has to be filled with Hylomar (permanently elastic universal sealant) BMW P/N 81 22 9 400 339.

In order to prevent damage to metal sealing surfaces when scraping off sticking pieces of gaskets, we recommend the use of gasket remover (BMW P/N 81 22 9 407 173) in conjunction with a hardwood scraper.

Cylinder Head Storage Cylinder heads must not be stored on their precision machined sealing surfaces; we recommend using wood boards or plywood sheets.

Cylinder Head Gasket Storage Cylinder head gaskets are supplied separately and have been vacuum-packed since May, 1982. The reason for this was that open-stored cylinder head gaskets would harden (dry out) and limit their storage time to about one year.
Please make sure that the plastic film is not damaged. The gasket package has an eyelet to make storage easier.



Handling and Application of Special Tool "TORQUE ANGLE TIGHTENING" A special tool attachment, which can be combined with the special tool (Order No. 11 2 110) for tightening connecting rod bolts, was developed in order to precisely tighten cylinder head bolts with the specified torque angle.

To tighten cylinder head bolts with the final value, the tool must be applied each time that the second socket rests on the opposite cylinder head bolt. In the case of unfavorably located cylinder head bolts (e.g. on firewall), 4 inch (10 cm) long 1/2" extensions must be used. In unloaded state turn ring of graduated dial to 0~ and lock with the knurled head screw.

Cylinder head bolts are tightened until the mark points to the dial value specified in the table (bolts tightened in proper sequence).