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Cam Timing Chain Marks On 1976-'88

The Automotive Engine Rebuilders Association (AERA) offers the following information regarding cam timing chain marks on 1976-'88 Isuzu 1.8L and 1.9L engines. Confusion may begin when reading the service manual information referencing marked plates on the cam timing chain. Apparently, some aftermarket timing chains don't have the marked plates which indicate the correct positioning for installation. The original equipment has two marked plates that must align with sprocket marks when properly installed.

To ensure correct installation of an unmarked timing chain, make sure that the correct number of links are between the cam and the crankshaft sprocket marks. Correct positioning of the sprocket marks also depends on which direction you are counting - clockwise or counter clockwise.

There will be 24 plates between the sprocket marks, counting in a clockwise direction, when properly timed. Counting counter clockwise, there should be 21 plates when the chain is properly installed. Both timing methods are viewed from the front of the engine. See Figure 1.

Engine Rebuilders: In a July 1994 technical bulletin, Ferrari North America, Inc. offered the following information regarding oil leaks in the area of the camshaft seal housing. Ferrari said that the leaks in many cases are caused by the marking of the sealing ring (p/n 117275).

When the gasket is replaced, rework the gasket by removing 1 mm of the material from the area which contacts the sealing ring (See Figure 2). Also, take care in the area between the two camshafts as the gasket must lay completely flat there.

As a further precaution it is necessary to chamfer slightly the cam cover itself (See Figure 3) in the areas shown. This chamfering can be done with light sand paper and will prevent the sharp edges of the cam cover from damaging the sealing ring upon installation.

It is important to use a high quality gasket sealer in the corners (not on the entire gasket) of the gasket where the gasket mates with other surfaces. Ferrari recommends Kar Products RTV (silicon adhesive/sealant 80257) or 3 Bond.

Ferrari says that from engine number 35334, this re-working of the gasket has already been performed at the OEM level. Prior to this engine number, the re-working had been carried out only on the following vehicles (See Chart 1).

Remember that in cases where repairs are being performed to eliminate leaks on early vehicles, it is important that besides following the procedure just described, the instructions detailed on Ferrari technical bulletin 10-31 (10/10/91) are also followed. It is not always considered necessary to replace the seal housing, the original housing may be modified as follows:

Machine a 1.5 mm chamfer around the seal housing using a lathe;

File a 2 mm draining groove in the bottom of the housing as shown in Figure 4.

Ferrari notes that the above described procedures are suggestions for resolving the occurrences of oil leakage and are not intended to be an update or service campaign. Ferrari says it is also possible to remove the fuel tank in order to replace one leaking seal, rather than to remove the entire engine assembly.

Brake Rebuilders: BMW notes that in some cars, especially those equipped with Jurid 506 brake pads, vibration in the body and steering while braking may be exhibited. When the brake discs are checked for runout, they frequently are found to be within specification.

This vibration is caused by the hard composition of the Jurid 506 pads which amplify any variations in the brake discs and the vibrations are transmitted into the body and steering. New brake pad compositions have been developed and tested for various models which greatly reduce the tendency to cause vibration.

The new style pads have been phased into production approximately as follows: E36 - 5/93; E34 M50 - 5/94; E34 M60 - 3/93; and E32 M60 - 9/93. There will be no production changes on the E31, E32-M70 or Motorsport models.

BMW says it is not necessary to replace the rear pads or discs to cure a vibration complaint. If the rear pads and discs currently on the car are not beyond specifications they do not have to be replaced. Whenever pads are replaced, all metal to metal part contact points of the pad and caliper should be lubricated with Plastilube, BMW p/n 81 22 9 407 103.

To prevent cold brake squeal when replacing pads on the E36 models only, all edges of the front pads should be chamfered with a file, cutting in 2 mm to a depth of 3 mm. See Figure 5. Apply Permatex Disc Brake Quiet to the back of the front pads, as per the manufacturer's instructions.

Engine Rebuilders: Nissan offers the following general information regarding valve train noise. Valve train noise is generally caused by improper operation of the Hydraulic Lash Adjusters (HLA) and is loudest in the cylinder head and valve cover area. HLA noise that occurs under all operating conditions is usually caused by a failed HLA. A failed HLA will compress easily and often will not return to its extended position.

Not all HLA noise is caused by a failed HLA. Keep in mind that HLAs require an adequate, air-free oil supply to operate properly. Air in an HLA's high pressure chamber will allow the lifter to compress under pressure, permitting excessive clearance in the valve train. If the rocker arm can be forcibly compressed by hand more than 1 mm (0.040"), it is highly probable that air is in the lash adjuster valve.

Air can enter a HLA in several ways. Excessive clearance between the rocker shafts and rocker arms can allow the HLA's oil supply to leak back to the engine's sump. When this occurs, the HLA will become oil starved and air can be easily drawn into the HLA. If there is a blockage in the oil supply, such as a clogged oil filter or clogged oil supply passage, air can also be drawn into the HLA.

The oil supply can become aerated if the engine is over filled with oil and the crankshaft beats it into a froth. The aerated oil can then easily be picked up by the oil pump and distributed throughout the engine. Aeration also occurs if there is leakage in the inlet tube to the oil pump, or at any of the associated seals.

Engine Rebuilders: In the Production Engine Remanufacturers Association's (PERA) May Current Concerns publication, a question was asked regarding cutting the rolled radius out of crankshafts. Remanufacturers were interested in knowing if you grind more than .010" under on the journal, which leaves very little rolled radius (about 50%), is this a problem?

Doug Anderson of Grooms Engines, Parts, Machining, Inc., Nashville, TN, says that he has found that it is okay to grind the journal flush with the "grooved" part of the rolled radius without creating problems. He notes that OEMs first cut the groove then roll the radius to give it a more dense grain structure which provides greater strength.

Anderson says that care should be taken when welding journals with a grooved or rolled radius to be sure that the groove is filled completely. Leaving an air pocket below the weld can create stress points that will lead to breakage.

Engine Rebuilders: In a May technical service bulletin the Automotive Engine Rebuilders Association (AERA) notes that its members have reported oversize valves and guides on 1990-'96 Ford 4.0L engines. It appears that some of these engines were released by Ford with oversize components. Ford also authorizes cylinder head service repair using oversize parts. The parts required, though, are limited at this time.

To make a successful repair, three component parts must be oversized - the valve, valve guide and valve stem oil seal. Ford currently has .008" (.20 mm) and .016" (.41 mm) oversize valves available, but only .015" (.381 mm) oversize stem seals. See Chart 2.

AERA says that it is unaware of any aftermarket suppliers of these oversize parts. Ford also authorizes conventional valve guide replacement if oversize components are not available.

Engine Rebuilders: Engine rebuilders should be aware that on 1990-'93 GM 1.6L, VIN 5 and 1.8L VIN 8 DOHC engines, the two internal oil control valves located below the intake camshaft are not included in a new cylinder head assembly.

In a May technical service bulletin, the Automotive Engine Rebuilders Association (AERA) notes that the valves must be either replaced or cleaned and transferred from the old head to the new casting. The oil flow check valve (p/n 94325538) and the oil control valve (p/n 94360288) are currently available from GM. Both valves are in the oil galley directly below the intake cam between the number 3 and 4 cylinders. See Figure 6.

The function of the oil flow check valve (603 in Figure 6) is to prevent oil from draining out of oil galleys in the head when the engine is stopped. The oil control valve (604 in Figure 6) meters the amount of engine oil going to the cylinder head.