FAI advises on common valve clearance issue

FAI Automotive has released advice on a common issue with the Mitsubishi 4D56/T, offering tips on valve clearance, recommending that essential adjustment between the valve and rocker arm is necessary.

FAI’s comprehensive range of valves and guides are manufactured to high-quality standards, with each part produced from high grade materials.

This is essential for modern engines that run at very high temperatures with a reduced stem diameter to minimise friction.

As a specialist in this area, FAI advises that in older applications that do not have a self-adjusting hydraulic tappet or lifter, such as the Mitsubishi 4D56, manual adjustment between the rocker arm and valve stem is a necessity.

When rebuilding the rocker shaft assembly, technicians should adhere to the manufacturer clearance specifications, says FAI.

To begin, the engine should be at operating temperature, before the technician ensures the timing marks are aligned correctly by rotating the crank manually.

The engine must be at operating temperature when setting valve stem clearances.

When these steps have been carried out correctly, FAI instructs that you will see that the following valves are in the raised position: Cylinder 1: Inlet & Exhausts; Cylinder 2: Inlet; Cylinder 3: Exhaust.

The technician should then adjust the clearances by firstly releasing tension on the rocker nut in preparation for the gauge.

Next, they need to place the correct feeler gauge between the valve and rocker (size will be specified by the manufacturer).

After this, the technician should begin tightening the screw while ensuring that the feeler gauge is met but not pinched, and then the lock nut needs to be tightened to secure setting.

Once this has been completed, the feeler gauge should be removed, before being reinserted to check there is a slight interference between the valve stem and the rocker arm.

Following this, the crankshaft needs to be turned 360 degrees clockwise. 

They then need to once again adjust clearances by releasing tension on the rocker lock nut, ensuring the correct feeler gauge is in place, and ensuring the screw is tightened and the feeler gauge is met, before tightening the screw and removing and reinserting the feeler gauge. 

While carrying out this step again, the following valves should be focused on: Cylinder 4: Inlet & Exhaust; Cylinder 2: Exhaust; and Cylinder 3: Intake.

Finally, to ensure the correct clearances are set and maintained, the technician should replace the rocker cover, run the engine for 10 minutes and then remove the rocker cover and check tolerances are still correcting the same gauge(s).

As a conscientious supplier, FAI has initiated a programme to mark every valve produced with the FAI part number, a factory code, and batch number. 

This information enables FAI to identify the valve or guide to the factory it was manufactured in and the date it was produced on. 

As its factory partners are ISO9001 & TS16949 certified, using this information the company can identify the material used, the foundry it was produced in, the QC records taken during its production, and even the workforce on that shift, providing complete reassurance and traceability. 

For more information on FAI Automotive’s range of valves and valve guides, visit: https://faiauto.com/parts/example-part-7/