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Valve clearance adjustment

A I@yab-look-oh

12 Posts

#1 · March 8, 2024, 6:52 pm

Quote from A I on March 8, 2024, 6:52 pm
Hey folks,
I've bought ZC32S a year ago with incomplete service history. Recently I've decided to do valve clearance check/adjustment.
Here's what I've ran into.
These are tips for people who have basic mechanic skills and not a complete guide.

Why checking / adjusting valve clearance on M16A is important?
M16A engine uses a shim-over-bucket valve train design that will reduce the valve clearance over time.
Because the valve sits deeper in seat as the seat wears down, the clearance between cam lobe and valve stem becomes tighter.
Too tight clearance would mean valve closes too late - up to a moment when hot gasses pass through the gap between valve and the seat and burn a hole in the valve.

When I checked clearances on my M16A all but one valve were out of spec - some just a bit, some were way off.
Adjusting the valve clearance requires to depress the valve while the cam lobe is facing up and swapping the shim to a different thickness until the gap is within spec.

To hold the valve depressed Suzuki manual suggests to use special tool(s) that attach to cam caps. It is necessary to undo cam cap bolts and install the tool. Three differently shaped tools are required because of varying positions of cam caps on different cylinders.

I did not want to do any of that so I researched how clearances are adjusted on other engines with shim-over-bucket valve trains. The closest I could find is Toyota, in particular 3ZZFE and 4AGE.
The tools are available on ebay for ~10-40EUR, though I knew they would need adjustment. The reviews of the chinese-made copy of the kit were very poor so I decided to buy the holder and use screwdriver to hold the valve open. Toyota/Lexus holder tool is straight and must be bent in a specific way to be used with M16A.
The holder I bought turned out too small anyway and did not provide enough gap to fish on the shim so I ended up fabricating a holder tool myself and file the ebay holder to act as valve opener instead. See pics below on the dimensions of the holder tool and valve train gap it must fit.

Measure the valve clearance with the feeler gauge and pop the shim to check the thickness marking on the downside.
Suzuki original shims come in sizes with 0.025mm step. Original turned out almost impossible to find in Germany - closest I got to is Fiat dealer (SX4 with M16A was sold as rebadged Fiat Sedici) quoting 15 EUR per piece - a blatant rip-off IMO. Metelli produces shims with 0.05mm sizes (p/n is 03-0-28XXX where XXX is marking on the shim, f.e. 245 is 2.45mm) that are 4-5EUR a piece on ebay. I managed to buy 5 shims of the sizes I needed but anything less than 2.4mm was out of stock, and I needed one 2.35mm and two 2.43mm too.

If you have access to bench grinder - its pretty easy to grind them down, spare shim bucket to hold the shim is super handy too. Go in small steps, check the size AND test-fit to be sure.
I do not have a grinder so I bought few sheets of sandpaper 120/240/400/800/1200 grit and spent an evening grinding =) Most of the work is done by 120 grit, when you are close to the desired size go with 240/400/800/1200 to smooth out the surface.

I realized that its possible to reshuffle the shims so I actually needed only 8 new shims and the rest of the gaps were set by moving shims from other valves to new places.
Don't forget to write down the sizes of installed shims, especially if you end up grinding some of them. Will be helpful for the person doing the next valve clearance adjustment )
Check out 3zzFE and 4AGE valve clearance adjustment videos on youtube to get an idea of what its like - the process is exactly the same minus the tool shape.

Pics:
Suzuki manual
Ebay Toyota/Lexus valve clearance tool
M16A valve train dimensions, top view
Holder tool, side view
Holder tool, top view

Hey folks,
I've bought ZC32S a year ago with incomplete service history. Recently I've decided to do valve clearance check/adjustment.
Here's what I've ran into.
These are tips for people who have basic mechanic skills and not a complete guide.

Why checking / adjusting valve clearance on M16A is important?
M16A engine uses a shim-over-bucket valve train design that will reduce the valve clearance over time.
Because the valve sits deeper in seat as the seat wears down, the clearance between cam lobe and valve stem becomes tighter.
Too tight clearance would mean valve closes too late - up to a moment when hot gasses pass through the gap between valve and the seat and burn a hole in the valve.

When I checked clearances on my M16A all but one valve were out of spec - some just a bit, some were way off.
Adjusting the valve clearance requires to depress the valve while the cam lobe is facing up and swapping the shim to a different thickness until the gap is within spec.

To hold the valve depressed Suzuki manual suggests to use special tool(s) that attach to cam caps. It is necessary to undo cam cap bolts and install the tool. Three differently shaped tools are required because of varying positions of cam caps on different cylinders.

I did not want to do any of that so I researched how clearances are adjusted on other engines with shim-over-bucket valve trains. The closest I could find is Toyota, in particular 3ZZFE and 4AGE.
The tools are available on ebay for ~10-40EUR, though I knew they would need adjustment. The reviews of the chinese-made copy of the kit were very poor so I decided to buy the holder and use screwdriver to hold the valve open. Toyota/Lexus holder tool is straight and must be bent in a specific way to be used with M16A.
The holder I bought turned out too small anyway and did not provide enough gap to fish on the shim so I ended up fabricating a holder tool myself and file the ebay holder to act as valve opener instead. See pics below on the dimensions of the holder tool and valve train gap it must fit.

Measure the valve clearance with the feeler gauge and pop the shim to check the thickness marking on the downside.
Suzuki original shims come in sizes with 0.025mm step. Original turned out almost impossible to find in Germany - closest I got to is Fiat dealer (SX4 with M16A was sold as rebadged Fiat Sedici) quoting 15 EUR per piece - a blatant rip-off IMO. Metelli produces shims with 0.05mm sizes (p/n is 03-0-28XXX where XXX is marking on the shim, f.e. 245 is 2.45mm) that are 4-5EUR a piece on ebay. I managed to buy 5 shims of the sizes I needed but anything less than 2.4mm was out of stock, and I needed one 2.35mm and two 2.43mm too.

If you have access to bench grinder - its pretty easy to grind them down, spare shim bucket to hold the shim is super handy too. Go in small steps, check the size AND test-fit to be sure.
I do not have a grinder so I bought few sheets of sandpaper 120/240/400/800/1200 grit and spent an evening grinding =) Most of the work is done by 120 grit, when you are close to the desired size go with 240/400/800/1200 to smooth out the surface.

I realized that its possible to reshuffle the shims so I actually needed only 8 new shims and the rest of the gaps were set by moving shims from other valves to new places.
Don't forget to write down the sizes of installed shims, especially if you end up grinding some of them. Will be helpful for the person doing the next valve clearance adjustment )
Check out 3zzFE and 4AGE valve clearance adjustment videos on youtube to get an idea of what its like - the process is exactly the same minus the tool shape.

Pics:
Suzuki manual
Ebay Toyota/Lexus valve clearance tool
M16A valve train dimensions, top view
Holder tool, side view
Holder tool, top view

Uploaded files:

S Illes@silles79

130 Posts

#2 · March 13, 2024, 10:30 am

Nice, I'm not sure I'm brave enough to attempt it.

How often would this needed to be done? Mine has done 80k miles, not sure if it has ever been done.

A I@yab-look-oh

12 PostsTopic Author

#3 · March 15, 2024, 10:37 pm

Quote from A I on March 15, 2024, 10:37 pm
AFAIR inspection should be done every 20k mi (30k km). I did on 130k km and it was way off, so if it was never done in 80k mi - I bet it should be adjusted.

I'd say this is relatively safe thing to do, not much can be irreversibly screwed up. Especially if you did other stuff like changing oil/filter, spark plugs and air filter.

First figure out is valves need adjustment at all:

Inspection is low risk and simple. Use ZC31 manual for instructions on how to remove and re-install valve cover - the engine is the same. If valve cover was not open for 80k mi - buy a new head cover gasket and sealant like Reinzolsil and de-greaser to clean the mating surfaces.
The specs are 0.2+-0.02mm on intake valves and 0.3+-0.02mm on exhaust.
Most common feeler gauge sets have 0.05mm steps so for intake 0.15 should be loose, 0.2 fit and 0.25 should not fit; for exhaust 0.25 should be loose, 0.3 fit and 0.35 should not fit. If 0.2 does not want to go in on intake side and 0.3 on exhaust - that's enough to conclude you need adjustment.

If valves do need adjustment:

Keep in mind that because over time the gap will reduce it doesn't hurt to go with upper limits of 0.22IN 0.32EX.
Check markings on all shims and write them down next to measured clearance for each valve. For this you would need to take out each shim, the marking is on the down side of it.
//hardcore math warning
Say you got 0.15mm and shim is S255 for one of the valves, 0.15 felt loose but 0.2 did not go in at all.
We'll assume this measurement is 0.175mm. It means the gap is 0.045mm too tight for a target of 0.22mm.
S255 shim marking means its 2.55mm thick, so you need thinner shim to increase the gap. Original shims go in 0.025mm steps, aftermarket in 0.05. S253 (OEM for 2.525mm shim) - is safe to use with the resulting gap of 0.2mm, aftermarket 2.50 is also be fine with resulting gap of 0.225mm, just slightly out of upper spec bound.
//hardcore math warning over

Few general tips:
- Best if you can afford to have car immobile somewhere - time pressure to get it back running does not help
- Jack up the front wheel and put it to 6th gear, rotate the wheel to rotate the engine, ALWAYS ONLY ROTATE FORWARD to keep the timing chain under proper tension
- Photograph things before taking them apart - for reference
- head cover bolts are 10Nm torque, but I do not have a wrench with this range. Bolts have stoppers on them so until you are doing this with your hands completely numb you will catch the moment tightening the bolt when it had hit the stopper. Tightening further will not compress the gasket more but will damage the winding in the head. Perhaps that's the worst thing you can do doing this job. The rest of actions are safe and reversible.

A word on feeling for feeler gauges:
- its hard to describe the amount of force exactly. I use this style https://cdn1.louis.de/dynamic/articles/o_resize,w_1800,h_1800,m_limit,c_fff/e4.2a.43.H1RothewaldFuehlerlehre20Blatt1003653691020.JPG and it should be possible to put the gauge in the gap while holding it around number engravings. If it flexes instead of going in - the gap is too small for that gauge.
- make sure the gauge is aligned with the gap and not binding to anything around it (on 1st cylinder there's very little space and it is tricky to guide it straight into the gap)
- once the gauge is in - move it back and forth - should feel tight and smooth, if it binds - too tight.

All that being said the clearance is 0.18 - 0.22 IN 0.28-0.32 EX so precise feeling is not important. If 0.15 is loose, 0.2 somehow goes in and 0.25 doesn't go at all - this is good enough. Is no rocket science )

AFAIR inspection should be done every 20k mi (30k km). I did on 130k km and it was way off, so if it was never done in 80k mi - I bet it should be adjusted.

I'd say this is relatively safe thing to do, not much can be irreversibly screwed up. Especially if you did other stuff like changing oil/filter, spark plugs and air filter.

First figure out is valves need adjustment at all:

Inspection is low risk and simple. Use ZC31 manual for instructions on how to remove and re-install valve cover - the engine is the same. If valve cover was not open for 80k mi - buy a new head cover gasket and sealant like Reinzolsil and de-greaser to clean the mating surfaces.
The specs are 0.2+-0.02mm on intake valves and 0.3+-0.02mm on exhaust.
Most common feeler gauge sets have 0.05mm steps so for intake 0.15 should be loose, 0.2 fit and 0.25 should not fit; for exhaust 0.25 should be loose, 0.3 fit and 0.35 should not fit. If 0.2 does not want to go in on intake side and 0.3 on exhaust - that's enough to conclude you need adjustment.

If valves do need adjustment:

Keep in mind that because over time the gap will reduce it doesn't hurt to go with upper limits of 0.22IN 0.32EX.
Check markings on all shims and write them down next to measured clearance for each valve. For this you would need to take out each shim, the marking is on the down side of it.
//hardcore math warning
Say you got 0.15mm and shim is S255 for one of the valves, 0.15 felt loose but 0.2 did not go in at all.
We'll assume this measurement is 0.175mm. It means the gap is 0.045mm too tight for a target of 0.22mm.
S255 shim marking means its 2.55mm thick, so you need thinner shim to increase the gap. Original shims go in 0.025mm steps, aftermarket in 0.05. S253 (OEM for 2.525mm shim) - is safe to use with the resulting gap of 0.2mm, aftermarket 2.50 is also be fine with resulting gap of 0.225mm, just slightly out of upper spec bound.
//hardcore math warning over

Few general tips:
- Best if you can afford to have car immobile somewhere - time pressure to get it back running does not help
- Jack up the front wheel and put it to 6th gear, rotate the wheel to rotate the engine, ALWAYS ONLY ROTATE FORWARD to keep the timing chain under proper tension
- Photograph things before taking them apart - for reference
- head cover bolts are 10Nm torque, but I do not have a wrench with this range. Bolts have stoppers on them so until you are doing this with your hands completely numb you will catch the moment tightening the bolt when it had hit the stopper. Tightening further will not compress the gasket more but will damage the winding in the head. Perhaps that's the worst thing you can do doing this job. The rest of actions are safe and reversible.

A word on feeling for feeler gauges:
- its hard to describe the amount of force exactly. I use this style https://cdn1.louis.de/dynamic/articles/o_resize,w_1800,h_1800,m_limit,c_fff/e4.2a.43.H1RothewaldFuehlerlehre20Blatt1003653691020.JPG and it should be possible to put the gauge in the gap while holding it around number engravings. If it flexes instead of going in - the gap is too small for that gauge.
- make sure the gauge is aligned with the gap and not binding to anything around it (on 1st cylinder there's very little space and it is tricky to guide it straight into the gap)
- once the gauge is in - move it back and forth - should feel tight and smooth, if it binds - too tight.

All that being said the clearance is 0.18 - 0.22 IN 0.28-0.32 EX so precise feeling is not important. If 0.15 is loose, 0.2 somehow goes in and 0.25 doesn't go at all - this is good enough. Is no rocket science )

Ian Frost@towie

1 Post

#4 · August 23, 2024, 1:00 pm

Hi new here, i just have done the timing chain, thought id have a look at clearances.
Mine are mostly higher, one at 35 on the exhust cam tolerance is 33.
One is 27 on exhust tolerance is 28.

Do i care if they are bigger gaps?

The original postwr was saying getting smaller was bad.
I figure bigger gaos may lead to lobe wear. But i have no idea

Thanks

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