Mazda 2 valve clearance adjustment - and beyond?

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Mazda 2 LPG
Hello all,

First post here on the forum concerning my Mazda 2 from year 2012. I really enjoy the car and haven't had any problems with it except for this one thing: Cylinder 1 currently has the smallest valve clearance buckets of 2.85mm installed. The other cylinders are on a close second.

After googling around a bit I found more stories of cars that had the smallest buckets installed. But then I found there are a few 'underground' methods to increase the life span of the cylinder head before going for a complete revision. For example: for another brand of car I found there are guys who shorten the valve tip a tiny bit and are still happily driving around (yes, this could ruin the hardened tip). Another more elegant solution I read about was using after market buckets with even smaller dimensions.

Of course I'm fully aware factory limits are exceeded and this is not recommended at all, but compared to a VERY expensive cylinder head revision this is interesting! And in my case it's even free. I can let my friend make the 2.85mm bucket into a 2.80mm. He can do this very precisely. And I am capable of removing the camshaft and replacing the buckets myself.

Now this does mean the valve would be seated 0.05mm deeper into the cilinder head. How bad (or not bad) would this be? I looked at a lot of pictures of naked cylinder heads with valve seats (naughty me..) and my educated guess is there must be at least 1mm of usable extra depth into the metal? (thought)


On a side note, for those who wonder why on earth this car is already on its smallest valve clearance buckets: It's a Mazda that runs on LPG-gas and Mazda didn't install hardened valve seats... (mad) And since I'm out of warranty there's nothing they will do. I was hoping to get to the 100.000km. This way I would have saved enough money because of the cheaper LPG to justify a complete cylinder head replacement and still have spare money. But currently it looks like I will finish at the 60.000km mark. Every 0.05mm extra will give me around 10.000km. So to get to the 100.000 mark I'd probably need a final bucket of 2.65mm
 

AN7

Mazda Addicted
Contributor
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Mazda2 1.5T Sport
I really really really can't understand your problem about the valve clearance.
The specifications of the valve clearance are 0.27mm to 0.33mm with the engine cold.
How much is your valve clearance?
 
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Mazda 2 LPG
I really really really can't understand your problem about the valve clearance.
The specifications of the valve clearance are 0.27mm to 0.33mm with the engine cold.
How much is your valve clearance?
Sorry, my bad for not being clear: The smallest available buckets (2,85mm) are currently installed. However, the valve clearance needs to be adjusted. It's now 0,22

This is a problem because I cannot buy smaller valve clearance buckets. 2,85mm is the smallest, but I will need 2.80 or maybe 2.75. That's why I thought about modifying the valve clearance buckets by myself. Just grind off another 0.05mm or 0.10mm and make them 2,80mm or 2,75mm. And when needed again in the future, just repeat.

I'm sure my engine won't explode instantly the first time I would do this, but everything has it's limits obviously.
 

AN7

Mazda Addicted
Contributor
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Mazda2 1.5T Sport
Grind the back of the valve if you want a cheap solution.
 
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Mazda 2 LPG
Thanks for the suggestion! Is there a specific reason you recommend this over grinding the valve buckets?

The only problem I can imagine with grinding that little extrusion inside the valve buckets is it might not be effective if the area around this extrusion starts hitting things. I have no idea how this valve bucket is actually seated on the valve. Do you know if this will actually work?

Sorry if I'm asking obvious things, but I really want to be sure!
 

flatlander937

Drives a clown car
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'11 Mazda2 Sport
What exactly is the problem? It sounds like you're looking for a solution to a problem that doesn't exist... Is it misfiring or what?

I've not pulled a Mazda2 cylinder head apart, is it possible to have a tiny shim made to go under the rocker arm pivot point to effectively gain some clearance? This may not be possible but I've not seen how the pedestal/fulcrum points are set up. Can you get a pic?

I've only really had to adjust some Honda valves so I'm throwing a wild suggestion based on that.


The other solution is to take a SLIGHT regrind on your cam all the way around, with a smaller base circle it will require more shim to get into spec.
 
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Mazda 2 LPG
What exactly is the problem? It sounds like you're looking for a solution to a problem that doesn't exist... Is it misfiring or what?

I've not pulled a Mazda2 cylinder head apart, is it possible to have a tiny shim made to go under the rocker arm pivot point to effectively gain some clearance? This may not be possible but I've not seen how the pedestal/fulcrum points are set up. Can you get a pic?

I've only really had to adjust some Honda valves so I'm throwing a wild suggestion based on that.


The other solution is to take a SLIGHT regrind on your cam all the way around, with a smaller base circle it will require more shim to get into spec.

The Mazda 2 doesn't use rocker arms. This is the type of system used:


Part number 12-966 is this part in real life:



The problem is the valve clearance is already out of spec. And although it doesn't misfire, running this engine on LPG with out-of-spec valve clearance is a very bad idea. Something needs to be done quick! Luckely I finally got a phone call from the garage that specializes in cylinder head revisions. He told me they sell aftermarket buckets that go to 2,70mm instead of 2,85 from original Mazda. Your idea about grinding the camshaft sound good too (although expensive I think)

So it appears these are my options:
1)Let the garage install those aftermarket buckets (will cost me 275 euro)
2)Grind off the existing buckets a bit (free and relatively easy)
3)Grind off the back of the valves (way more difficult, and risking to ruin the hardened tip from the valve)
4)Grind the camshaft (This is probably expensive right? Can't do this myself...)

Unless there are other idea's I think I will go with option 2 and just repeat in the the future till something breaks. Then I'll do the expensive cylinder head revision.
 

AN7

Mazda Addicted
Contributor
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Mazda2 1.5T Sport
With the clearance smaller than the specks you are about to worn the camshafts and the buckets/tappets.

Grinding the back of the valve is way more easier than grinding the bucket. You can do it by your self with a water sandpaper.
Anyway, the reason that your clearance is smaller than the specs is either because the valve seats are f@cked up or the valve its self :p
With that in my mind I wouldn't care if I ruin the hardened tip.
 
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2011 Mazda2
When you say the back of the valve, are you referring to the tip?

And to the question about grinding down the top of the bucket; not a good idea as the top is slightly concave to make the bucket rotate in operation. If you need to solve for a smaller clearance, simply grind the tip to bucket "tit" using a mill and carbide flat stone
 
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Mazda 2 LPG
The reason the clearance is already smaller than the specs is because the car runs on LPG and Mazda didn't add hardened valve seats. I didn't add the LPG installation afterwards by the way, the car came with the LPG installation brand new from the Mazda factory. Mazda is now replacing the whole cylinder head for free because they know they f@cked up. The problem is they only do this when you do all the maintenance at the official Mazda dealer... which I didn't. So that's the backstory of this problem.


Yes, I was talking about grinding of the little 'tit' inside of the bucket, not the top that touches the camshaft of course. Thanks for the tip though!

@AN7
Doesn't mean grinding of a bit of the back of the valve I need to remove the valves completely from the engine? Which in turn means the need to remove the whole cylinder head? I mean, it still sounds like a lot more work!
 

AN7

Mazda Addicted
Contributor
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Mazda2 1.5T Sport
The dealers installed the lpg, not the mazda per se.

No, I was saying to grind the back with the head on.
But if you can "shave" the bucket for free, go that way.
Set the clearance to 0.3-0.35 but with the valve seats collapsing there is a possibility to broke apart and ruin your motor.
 
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Mazda 2 LPG
Yes, you're right. In fact the LPG is installed in Belgium before the car is imported to the Netherlands. A trick to circumvent certain taxes.

Will go for the buckets then. The max I can shave off is 0,85mm. This would give me at least another 80.000km and probably a bit more. Worth the risk in my case.

We'll see how it goes. Will post back here in the future
 
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Mazda 2 LPG
For those who are interested: Meanwhile I have done the valve clearance adjustment two times myself. First one at 47.500km. I set the clearance of the outgoing exhaust valves to 0.35mm each by grinding off a tiny bit of the inside of those valve buckets. 48.000km later (at 95.500km) clearance adjustment was needed again. Cylinder 1 had a clearance of 0,20mm and 0,23mm for the exhaust valves and was out of spec. The others were all still at around 0.28mm. I choose to grind them all and set the clearance to 0,40mm for each of them. Yes, that's a tiny bit bigger and but means I can have longer intervals.

So in 48.000km the wear on cylinder 1 was about 0,15mm. That's about 0,07mm per 25.000km. The other cylinders showed even less wear (no idea why) But anyway, with buckets that have 0,85mm of 'room', this could be done at least 10 times based on the wear of cylinder 1... probably more. Car is now at 115.000km and I will check again soon what the valve clearance is. I expect somewhere between 0.30 and 0.35, so hopefully no adjustment needed.

Relaxing that timing chain in order to be able to remove those camshafts is a real pain in the ass by the way. You have to push a tiny screwdriver into a tiny hole on the side of the engine in order to release the timing chain tensioner mechanism. Meanwhile you have to wiggle around both the screwdriver and the chain itself in just the right way. That's like solving a puzzle blindfolded using only 1 finger. Even the garage could't do it and ended up removing the whole side of the engine: See this video where the whole side of the engine has been removed, including the timing chain. That little metal thingy you have to hold in order to relax the timing chain is normally behind the side panel of the engine and only accessible via at tiny hole.

Second time when the valves needed adjustments I decided to enlarge that tiny hole with a drill to the size of a 1 euro coin. So now I can actually see that mechanism and tell what i'm doing without removing the whole side. Now its easy to release the chain. Of course I had to make a metal lid to close the hole afterwards because the tiny screw that normally closes the hole doesnt fit anymore. Anyway, so far so good and I thought to let u guys know how it went ;)
 
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