Cosworth YB Manual - Section Repair - Cylinder Head
 

PART A - Engine, Engine Management and Turbocharger

1.2 Repair Information

Important Notes on Cylinder Head - Removal and Installation

Note: Before slackening the head bolts the engine should be allowed approx. 2 hours to cool off.

The fuel feed pipe can be removed using the new special tool 23-023.
Open special tool and slide over the fuel pipe as shown in illustration. Push tool against pipe fitting.

Remove the timing belt cover.

There are:
- two spacers fitted between the valve cover and the timing belt cover, - one spacer (with washer) screwed into the cylinder head
- and one spacer screwed into the engine block.

Before removing the timing belt the first cylinder should be set to TDC as follows:
- Turn crankshaft to a position where the flank of the tooth on the V-Belt pulley (1) aligns with the TDC marking on the cover.
- The timing marks of the two camshaft sprocket gears must align with the cylinder head upper edge.

Removal of fuel feed pipe
1 = Fuel feed pipe
2 = Special tool 23-023 3 = Fuel rail

Crankshaft in TDC position
1 = TDC marking
2 = Ignition timing mark (16° BTDC)

1.2 Repair Information (Important Notes on Cylinder Head - Removal and Installation, cont'd.)

- The timing mark on the sprocket gear for the auxiliary shaft must align with the marking on the engine block.

In this position, the distributor rotor will be in No.1 TDC position.

Slacken timing belt tensioner (one nut) and remove timing belt.

Important: Do not crank the engine with the timing belt removed. This will cause serious damage to the valve train and the pistons .

Slacken cylinder head bolts starting trom the middle of the head. Remove bolts with washers.

When installing the cylinder head gasket fit alignment studs as shown.

Auxiliary shaft and distributor rotor it, tdc position

Slackening and tightening sequence for the head bolts

Alignment studs

Lubricate head bolts at threads and under bolt head and install bolts together with washers.

Tighten cylinder head bolts as follows:

Stage 1 requires to tighten all bolts 30-35 Nm.
Stage 2 requires to tighten all bolts to 67 -70 Nm following the sequence.
Stage 3 requires the bolts to be tighten in degrees of rotating using a special gauge tool.

Following the sequence, each bolt is turned 80° - 90° of rotation .

Check and ensure that the crankshaft, the camshafts, the auxiliary shaft and the distributor rotor are still in TDC position. Fit the timing belt in counter*clockwise direction starting at the auxi*liary gear.

• Pull belt tensioner by hand in clockwise direction against the timing belt and tighten fastening nut.

Crank engine several times in clockwise direction and subsequently one full turn counter - clockwise to TDC position.

Note: The engine must not be cranked beyond TDC position.

Using the belt tension gauge 21-113, check belt tension at the longest straight section (see illustration). If necessary adjust belt tensioner so that the specified tension of 9,5 to 10,5 is achieved.

Repeat complete procedure and recheck belt tension.

Crankshaft, camshafts, auxiliary shaft and distributor in tdc position

Checking and adjusting belt tension

Fit valve cover using a new, dry gasket. Then finger tighten all bolts. Subsequently torque bolts to specification, beginning with the inner bolts and ending with the outer bolts. Then tighten the flange bolts to specification.

• Install timing belt cover making sure the spacers and washers are correctly installed.

To remove the camshafts, untighten bearing caps carefully in equal steps, remove caps and then lift the camshafts from the supports.

The bearing caps are marked by numbers starting at the front ball bearing 1 to 5 on the exhaust side and 6 to 10 on the inlet side.

The bearing journals of the camshaft for the inlet side have oil grooves.

The camshafts must not be inter*changed.

The bearing caps will fit one way only *incorrect installation is therefore not possible.

When fitting the camshafts, make sure that the front bearing retainers are flush with the bore in the cylinder head. The bearing retainers are pre*vented trom tilting by a screw and washer from below (see illustration).

First fit bearing caps 2 to 5 and 7 to 10 and tighten them equally starting with the inner ones.

Ensure both front bearing retainers are still flush before fitting the caps
1 and 6. Subsequently torque all nuts with the specified torque (see Technical Data).

Identification of bearing caps 1 = Support with ball bearing

Camshaft for the inlet valves Bearing journal with oil groove

Camshaft front bearing
1 = Retainer in flush position
2 = Bearing retainer
3 = Securing screw

The camshaft once removed from the cylinder head can be disassembled as follows:

The camshaft sprocket gear is fixed on the camshaft by a keyway with
key (8).

Unscrew fastening bolt and remove the sprocket gear (1). Remove key (8) and pull oil seal race (2) and bearing retainer (6) from the camshaft (9).

Lever off oil seal (3) from the bearing retainer (6).

The ball bearing (5) has a press - fit in the retainer (6) and is secured by a snap ring.

The bearing can easily be pushed out of the retainer (if necessary with light hammer blow on the bearing outer ring or by using the handle of
a hammer).

New rubber '0' rings (7) should be used when reinstalling the camshaft.

The oil seal can also be replaced with the camshaft in situ. This requires removal of the sprocket gear and the oil seal race. Then, the oil seal can
be removed using the special tool 21-096.

The hydraulic valve tappets are supp*lied as an assembly and must not be dismantled.

Removal of a hydraulic tappet can be done easily using a suitable sucker.
Note: Removal of hydraulic tappets should not be done with a magnet.
Tappets should not be mixed up and should always be installed in their original sequence .

When installing, tappets should be lubricated .

When applying pressure to the hydrau*lic plungers some tappets may feel "soft" due to air in their hydraulic chamber. This may be ignored because it will disappear once the engine is running again.

Camshaft assembly

Special Tool 21-096

To remove the valves, the new adaptor 21-024-06 for the valve spring compres*sor 21-024 must be used. Make sure that the valves stems are not damaged by the valve spring retainer when it is pressed down to remove or install the valve collets.

Remove the valve retainers, the springs and the valves.

Remove the valve stem seals using a suitable tool (as known from the 1600 Diesel engine) as shown. Subsequently remove the lower spring retainer.

When assembling, first fit the lower spring retainers.

Then lubricate the new valve stem seals and press them onto the valve guides using the special tool 21-130 for the inlet side and the special tool 21-129 for the outlet side as shown.

Please remember, that the valve stem seals have different diameters
(inlet side - 7,0 mm, outlet side - 8,0 mm).

Lubricate the valve stems before inserting the valves into the valve guides.

Removal of valves
1 = Valve spring compressor 21-024
2 = Adaptor 21-024-06

Removal of valve stem seals

Installation of valve stem seals

In the case of replacing the valve stem seals with cylinder head in situ, a suitable adapter for the pressure hose should be used.

Note: For this procedure crank engine by hand, that all pistons are in the same position in the cylinder bores and then lock the crankshaft.