Procedure of tappet adjustment - 1986 Suzuki Samurai

The valve clearance specification for a 1998 Hyundai H100 2.6 diesel bakkie is:
Intake valve clearance: 0.25 - 0.35 mm (0.010 - 0.014 in) Exhaust valve clearance: 0.45 - 0.55 mm (0.018 - 0.022 in)
The tappet setting for this engine will depend on the specific valve clearance measurements for each valve. If the valve clearances are found to be outside of the specification, the tappet settings will need to be adjusted accordingly. It is recommended to refer to the manufacturer's service manual for detailed instructions on how to perform the adjustment procedure.

Question edited for clarity.

The cam followers have the adjustment and have to be replaced. They don't have adjustable tappets as such. Note spelling 'tappets', not 'tuppets'.

http://www.nisentra.com/camshaft_valve_clearance-411.html

https://www.google.com/search?q=Tappet+adjustment+for+1988+B12+auto+engine+Nissan+Sentra

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You have asked a very big question. Adjusting the tappets is another way of saying adjusting the valve clearances.

Lots of engines these days are fitted with hydraulic tappets that are self-adjusting. Some engines are overhead camshaft types with bucket tappets and the clearances are adjusted by measuring and selecting different thickness shims. The shims are sometimes under the bucket and sometimes over. The former is a fairly big and complex job to adjust and the latter is fiddly and requires much patience.

Traditional designs using adjusting screws and locknuts exist on all manner of engine types and once the principle of which one to adjust when is learned, these are relatively straightforward.

I strongly suggest you discover first what sort of tappets you need to learn to adjust, learn something about the way the engine works and why the tappets need periodic adjustment and then pay somebody to show you how to do the job so next time you will be able to do it yourself.
Adjusting the tappets is one of the core skills of the mechanic and it is learned better by demonstration and understanding than from a book. No book can adequately describe when a feeler blade has a good or a bad "feel"...

Good luck!

The firing order is 1-3-4-2. The gap is listed on the emission information sticker under the hood. This sticker will have lots of info which includes valve lash. It will be listed in millimeters, example: 0.22 +/- .02mm. Some feeler gauges list both standard and mm measurements, otherwise a conversion can be found without much trouble. This procedure should be done while the engine is cold to get the best results.

this is from the AutoZone web site.

2.9L Engine
No periodic valve lash adjustments are necessary on this engine. The engine utilizes a hydraulic valvetrain to automatically maintain proper valve lash. However, some earlier models have an adjusting screw on the rocker arm, which is used when assembling the engine to properly preload the lifter. If the engine has been disassembled, and the valve train parts were not kept in order, or there is an audible sound from the rocker arms while the engine is running, perform the adjusment procedure below.
The following procedure should be performed on a cold engine.

1. On the cylinder to be adjusted, position the cams so that the tappets are in the base circle area.
2. Loosen the adjusting screws until a distinct lash between the roller arm pad and the valve tip can be noticed.

The plunger of the hydraulic tappet should now be fully extended under the load of the internal spring.

1. Carefully screw in the adjustment screws until the roller arms slightly touch the valves.
2. To achieve the normal working position of the plunger, screw in the adjusting screw 1 1 / 2 turns, equivalent to 2mm.


here is the site address. scroll down the page & you will see your engine size - 2.9

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Both the 2.0 liter 4-cylinder, and the 2.5 liter V6 are overhead cam engines. While all years of the V6 us hydraulic tappets, the 4-cylinder engines varied. From 1998 and earlier, they had hydraulic tappets. From 1999 on, they used shimmed mechanical tappets. Adjusting valve clearance on the later engines is a little involved, and, if you're not familiar with the procedure, it is perhaps best left to a professional mechanic who is familiar with the engine.

If you have adjustable tappets bring the engine to top dead center no 1 piston firing The rocker will be on the back of the cam lobes. Inlet .010" hot exhaust .012" hot and then turn until next firing piston is in position. Go by firing order. I suspect that a 1997 model would have hydraulic adjusted tappets which means no manual adjustment. If it is rattlly I would be checking for worn rocker shaft and rocker bushes.

Hydraulic tappets are tappets that contain a small hydraulic piston, pressurised by the engine's lubricating oil supply.[5] Although the piston does not move appreciably or frequently, it acts as a hydraulic spring that automatically adjusts the tappet clearance according to the oil pressure. This makes the valve actuation self-adjusting and there is no need to adjust the rockers. Hydraulic tappets depend on a supply of clean oil at the appropriate pressure. When starting a cold engine, with low oil pressure, hydraulic tappets are often noisy for a few seconds, until they position themselves correctly.


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Why?
If they are noisy (hydraulic tappets, remember?), try an oil/filter change first with a little Gunk cleaner in the crankcase before draining.
If that does not help and you seriously want to do this, do yourself a favor and get a Bently Service Manual.
The basic adjustment is "2 turns tighter (clockwise) after all lash is removed and the adjuster is just touching the valve stem." Although in practice 1.5 turns seems to work better.
GET THE MANUAL for the proper procedure including sequence as the cam must be on the base circle when you do it or the adjustment is no good.

When setting tappets, it has to be born inind that the valve stem wears an indentation into the face of the rocker. This prevents a really accurate tappet adjustment, so the customer is right again. If you do not posess a tappet setting dial gauge, a normal engineers dial gauge will do just as well. The procedure is the same as using your feeler gauge except that you set the dial gauge up on the cylinder head with the pointer resting on the head of the rocker. Press down fairly firmly on the rocker valve end and zero the gauge. Next lift up on the rocker and read off the clearance, from the gauge, Use a magnetic base to support your gauge and repeat the pocedure for each valve pair.