Hayden
If your 1HZ or 1HD-T has started ticking at idle, or it’s due for a big service and nobody can remember the last time the valves were checked, this one’s for you. Setting the valve clearances on these engines is a job most home mechanics can do in an afternoon.
You need a feeler gauge, a micrometer, one special tool and some patience.
There are no rocker adjusters to wind in and out.
Instead, a small shim on top of each bucket sets the gap, and you swap shims to change it.
Below is the whole process, the specs, the maths for picking a new shim, and the mistakes that catch people out most often.
Short answer: what are the 1HZ and 1HD-T valve clearances?
Check them with the engine cold. The factory specification is the same for both engines:
| Valve | Clearance (cold) | Aim for |
|---|---|---|
| Intake | 0.15-0.25 mm (0.006-0.010 in) | 0.20 mm |
| Exhaust | 0.35-0.45 mm (0.014-0.018 in) | 0.40 mm |
Anything inside the range is fine and can be left alone. Anything outside it needs a different shim.
Which engines does this cover?
This guide is for the 12-valve 1HZ and 1HD-T. The 1HZ is the 4.2L non-turbo diesel fitted to the Toyota LandCruiser 70 Series, 80 Series and 105 Series. The 1HD-T is the direct-injection turbo diesel from the Toyota LandCruiser 80 Series. Both use the same head layout, the same clearances and the same method.
It does not cover the 24-valve 1HD-FT or 1HD-FTE. Those heads are different.
How does a shim-over-bucket valve train work?
The camshaft sits directly above the valves. Each cam lobe presses down on a cup-shaped bucket, also called the valve lifter, and the bucket pushes the valve open. A flat, round shim sits in a recess on top of each bucket, between the bucket and the cam.
When the lobe is pointing away from the bucket, there should be a small gap between the cam and the shim. That gap is the valve clearance. A thicker shim closes the gap up, a thinner one opens it.
Why it matters:
- Too loose and the valve train gets noisy, the valve opens late and closes early, and the cam and shim wear faster from the hammering.
- Too tight is the one to worry about. The valve may not seat fully, so it can’t pass its heat into the head. Run it like that long enough and you burn an exhaust valve. Clearances usually tighten as valves and seats wear, so a quiet engine isn’t proof the gaps are right.
What tools do you need?
| Tool | What it’s for |
|---|---|
| Metric feeler gauge set | Measuring the gap between cam and shim |
| Micrometer, 0-25 mm | Measuring the thickness of the old shim |
| Valve lifter depressor tool | Holding the bucket down so the shim can come out. It hooks under the camshaft and presses on the edge of the bucket. |
| Small flat screwdriver and a magnetic pick-up tool | Lifting the shim out of the bucket |
| Socket and breaker bar on the crank pulley bolt | Turning the engine over by hand |
| Pen and paper | Recording every reading. Don’t trust your memory. |
The depressor tool is the one people don’t have. A screwdriver levered against the cam will slip, and it can gouge the cam or send a shim flying into the timing gear area.
Step 1: get the engine cold and the cover off
The clearances are cold specs, so let the engine sit overnight if you can. A warm engine will give you false readings.
Remove the intake pipe that runs across the top of the engine, then the rocker cover. Have a new rocker cover gasket and seals on hand for the rebuild. The old ones are usually hard and won’t seal a second time.
Step 2: set No.1 cylinder to TDC on compression
Turn the crankshaft clockwise, the normal running direction, with a socket on the crank pulley bolt. Line up the groove on the crankshaft pulley with the timing mark on the timing gear cover.
The pulley mark lines up twice every cycle, so you need to know which one you’re on.
Look at No.1 cylinder, at the front of the engine.
Both of its buckets should be loose, with a gap under the cam, and both buckets on No.6 should be tight.
If it’s the other way around, No.6 is on compression. Turn the crank one more full turn and line the mark up again.
Always turn the engine clockwise. If you overshoot the mark, keep going around rather than backing it up.
Step 3: measure the first six valves
With No.1 on compression, six of the twelve valves have their cam lobes pointing away from the bucket. Those are the ones you can measure now. Cylinders are numbered from the timing gear end at the front to the back.
| Crank position | Intake valves to check | Exhaust valves to check |
|---|---|---|
| No.1 at TDC compression | Cylinders 1, 2 and 4 | Cylinders 1, 3 and 5 |
| Crank turned one full turn, No.6 at TDC compression | Cylinders 3, 5 and 6 | Cylinders 2, 4 and 6 |
For each valve, slide the feeler gauge between the base of the cam lobe and the shim.
You want a light, even drag. If the blade drops through with no resistance, go up a size.
If you have to force it, go down. The reading is the thickest blade that goes in with that light drag.
Write every reading down, including the ones that are in spec. Mark the ones that are out. You’ll use those numbers to pick the new shims.
Step 4: turn the crank once and measure the other six
Turn the crankshaft one full turn, 360°, clockwise and line up the pulley mark again. No.6 is now on compression. Measure the remaining six valves from the second row of the table and write those down too.
If every reading is inside spec, you’re done. Skip to step 7 and put it back together.
Step 5: remove the shim from each valve that’s out of spec
Work on one valve at a time:
- Turn the crank until the cam lobe for that valve points straight up, away from the bucket.
- Turn the bucket so the notch in its rim faces the exhaust manifold side of the engine. That notch is where you get the screwdriver in later, and it needs to be reachable once the tool is on.
- Fit the depressor tool and press the bucket down, away from the cam.
- Slip a small screwdriver into the notch, lift the shim, and pick it out with the magnet.
Keep each shim with its valve. A labelled egg carton or a strip of masking tape on the bench with the valve positions written on it works well.
Step 6: work out the new shim size
Measure the old shim with the micrometer. The size is etched on one face, but shims wear, so measure it rather than trusting the number.
Then use this formula, where T is the thickness of the old shim, A is the clearance you measured, and N is the new shim you need:
| Valve | New shim thickness |
|---|---|
| Intake | N = T + (A – 0.20 mm) |
| Exhaust | N = T + (A – 0.40 mm) |
All the formula does is take the gap you’ve got, compare it to the middle of the spec, and change the shim by the difference.
Example 1, a loose intake. You measure 0.32 mm and the old shim mics at 2.80 mm. 0.32 – 0.20 = 0.12, so N = 2.80 + 0.12 = 2.92 mm. The nearest available size is 2.90 mm. That gives you a clearance of 0.22 mm, right in spec.
Example 2, a tight exhaust. You measure 0.30 mm and the old shim is 2.75 mm. 0.30 – 0.40 = -0.10, so N = 2.75 – 0.10 = 2.65 mm. Fit a 2.65 mm shim and you’re back to 0.40 mm.
Shims come in 0.05 mm steps, from 2.35 mm up to 3.30 mm, 20 sizes in all. Pick the size closest to your calculated figure. If it falls exactly halfway, either size will land inside the range.
Need shims? We sell the 2.50-3.30 mm sizes one at a time, so you only buy the ones your readings call for. Pick them from our valve shims suitable for 1HZ and 1HD-T.
If you do this job often, or you’d rather not wait on a second order when a calculation lands on a size you didn’t buy, get the valve shim workshop kit. It has three of every size from 2.50 mm to 3.30 mm, 51 shims in all.
Step 7: fit the new shims and check again
With the depressor tool still holding the bucket down, drop the new shim into the recess. Fit it with the etched size facing down, towards the bucket. That keeps the cam off the markings, so you can still read them next time. Make sure it sits flat, then remove the tool.
Once every new shim is in, turn the engine over by hand two full turns. That lets everything settle and proves nothing is binding. Then measure all the valves you changed again. If one is still out, repeat steps 5 and 6 for that valve.
When you’re happy, refit the cylinder head cover with the new gasket and seals, then refit the intake pipe. Start it up and check for oil leaks around the cover.
What goes wrong most often?
- Measuring warm. The engine grows as it heats up, and the readings change with it. Do it cold.
- Being on the wrong TDC. If you measure valves that are partly open, the readings mean nothing. Check that No.1’s buckets are loose before you start.
- Turning the engine backwards. Always turn it clockwise from the crank pulley.
- Losing track of which shim came from where. Label everything as it comes out.
- Trusting the number on the shim. Measure the old one. A few hundredths of wear is enough to put your new clearance out.
- Forgetting the notch. If the bucket notch isn’t facing the exhaust side before you press it down, you can’t get the shim out without taking the tool off and starting again.
- Using a pry bar instead of the proper tool. It’s the quickest way to damage a cam lobe.
HD Automotive is an independent business and is not affiliated with or endorsed by Toyota. Toyota and LandCruiser are trademarks of Toyota Motor Corporation, used here only to describe which vehicles this guide applies to.
