Yeah, luckily on this engine the shims are at the top of the bucket; they can be pryed up with a screwdriver and then pulled out with a magnet with the cams still in place.
How did the clearance get so tight? It’s as if (don’t laugh) the shim expanded or what?
Turn the engine so that the lobe is up. What happened is that the valve face or the face on the valve seat eroded away, raising the stem up. There is also the possibility (slim, very slim) that a keeper came loose and is keeping the bucket from going all the way down onto the stem. You will probably have to remove the bucket to see the keepers and that will probably mean removing the cam.
I suppose that it is also possible that there is some carbon buildup under the bucket, but I don’t see how that could happen.
The reason I mention only adjusting the tight one is because I assumed that you may do this yourself and the others are in tolerance. If this is done at a shop they should inspect and adjust all of them as necessary.
Why do valves tighten up? For several reasons. With miles the valve face has a tendency to dish and/or the valve seat has a tendency to recede; both of which sink the valve deeper and thus closer to the adjuster.
Valve stem stretch also occurs due to engine heat and the valve being slammed down repeatedly onto the seat.
This can be especially true if the engine has suffered overheating in the past and exhaust valves are more prone to stem stretch than intakes, although it can occur with either.
Methinks that the Wet test you did on the cyl with 150 points to a valve issue… (I think Mr Circuitsmith nailed it) Before it was 150 dry and then wet it would have been higher if it were ring related… that’s a valve issue… Which is actually great news…totally fixable.
The guys also nailed the reasons why valve lash can tighten up… Which is also great news…the bad news is that you really need to know what you are doing in order to determine what shim size you now need…That process is too long for me to writeup…but the info is out there for you to peruse…
In the past I have cut my own “too thick” shims down by hand with a Dremel, a micrometer and a set of feeler gauges…in my driveway no less… I did 12 of them on a Saab 900… My Dad thought I was nuts…but said good job when the engine was running with no valve lash noise…it ran perfect…But none of this was easy I should say…it took a lot of patience and a steady hand…
Now I don’t recommend this unless you think you can pull it off… The other way is to order yourself a bunch of thinner shims and have at it…but… You now have a valve stem shim that is too thick…which means if you carefully remove material from it…eventually you will get it to the right thickness and the valve will seat properly…and all will be right with the world again…
I’m having a hard time finding a place that sells the shims. The Local Mazda dealer doesn’t even stock them. I have been thinking about doing what you mentioned Blackbird and filing them down. On the one with zero clearance would all I need to do is remove .010’’-012’’ to bring it back into spec.? is it that simple? Or is there any reason why I couldn’t take it to a machine shop and have them file it down?
It’s a bit ridiculous that the Mazda dealer doesn’t stock shims. How in the world do they do (allegedly) any service work pertaining to the cylinder head and valve train?
I would advise that the shim not be filed or taken to a machine shop for surfacing. Valve shims are normally hardened and if the hard surface is removed on one side the shim could wear down or become crushed down and this will lead to excessive clearance.
If you know what shim thickness is in there now on the tight valve you might contact the Mazda dealer service department as to whether they keep a shim kit in the service dept.
Sometimes this is done with shims being swapped around as necessary and at no charge to the customer.
If they don’t have a shim kit for use in the shop I don’t know what to say about their methodogy.
If it came down to absolutely, positively, removing metal then I’d brush the top of the valve stem with a Dremel tool rather than grinding on the shim.
True OK44 said it…they should have a SHIM KIT for that vehicle… At least the service dept should…
AND DO NOT GRIND YOUR VALVE…they aren’t as easily replaced as a little shim…Obviously…
You CAN do this yourself if you trust that you have the skills. You CAN go to a machine shop and tell them the EXACT amount of material to remove…BUT THIS IS WHAT YOU DONT KNOW…and what you are trying to figure out!!
The issue here is that you dont actually know the amount of material to remove…you CAN do this… Measure on another valve…is it the exhaust you are working on? Whichever valve you are trying to get the clearance on…go to its match on the next cyl…measure the clearance between the cam and the top of the bucket… NOW…go to your tight valve…you need to set up a sort of spring compressor…it may be a large prybar… Then push the valve in until you get the proper feeler gauge clearance…try to transfer the amount you depressed the bucket…to the shim… I know its seat of the Pants-ish…but if you’re good you will eventually get the correct amount of material off the shim to create the clearance you need… The problem you have is that you don’t know how much material to remove… Try to formulate a way to determine this…I know its hard but try…
Or you can try to remove a very small amount of material and test…over and over again… Its a lot of work…and it was a lot of work for me…but I did it… ON 12 SHIMS…talk about fun… But I DID have fun and took the issue by the balls and with skill and patience knocked it out of the park. But honestly this is a CRAZY way to do it… you need a too thin shim…this will reveal all…
You CAN do this…its just going to take a while…
WHAT I DID …was to have a bunch of extra shims…so I could measure the shim in the too tight valve…and then scale the others down… and continue to try them… BUT YOU NEED MORE SHIMS…bec you are prob going to F things up at least once or twice… What you REALLY need is a too thin shim…which you can make if you have extras… This too thin shim…will give you the exact amount of material you need to take off the Too THICK shim… Get me?
But having extra shims is almost absolutely essential…I had them and it helped me tackle the issue… You need them too… THEY MUST BE AVAILABLE… Insert a too thin shim… note the excess clearance with feeler gauges…then compare the too thick to the too thin…an factor in what clearance you want…AND YOU’VE GOT IT… THIS IS THE SOLUTION… But you need more shims…did I mention you need more shims yet? LOL
Look online to see if you can find a valve shim kit for your car…it will have a TON of shims at varying thickness… GIVE IT A SHOT…
Blackbird
Another, much simpler option would be to buy shim stock in the thickness you need, and then cut out a shim using tin snips and the old shim as a guide.
I have the solid disc/shim/spacer/? removed - the one directly under the cam lobe. There’s what looks like another shim in there. Or is it the shim? Does that come out too? I’m a little confused - my manual makes it look like there’s only one shim and that it’s at the top of the bucket.
The shims are nowhere near a thickness that would even approach cutting with tin snips…at least in my experience… they are usually over 1/8th of an inch of micro polished…EXACT fitting round shims… They most often fit into a subsequent round receptor hole so they cannot move around.
The shims I have done were all over 1/8 twd 1/4 inch thick steel… I have no clue where you would find any type of steel stock that would fit this exacting spec.
I will look up what your shim is…however it is usually “shim UNDER bucket” …No? so you would need to take off material on the item UNDERthe bucket…if you mess with the top of the bucket…you will never get the finish back perfect enough to not mess up the smooth polished cam surface.
Let me do some research and make sure your shims are UNDER the buckets like they should be…
Incidentally is Keith correct about the thickness here? IN my experience the shims are QUITE thick…way thicker than a tin snip will work with.
Can you send me a picture? Do you have any extra shims? Because I REALLY need you to have a thinner shim… MAYBE we can remove the shim all together…and then calculate the amount of material…by measuring the now too much clearance between bucket and cam…factor that in with your shim thickness…and subtract…then slowly remove material…and stop when your close…but on the thick side… measure again etc…
Do you understand what I am telling you… I am trying to be clear but…
DOES IT LOOK LIKE THIS?
Methinks it does…the SHIM…is UNDER the bucket…hence the phrase…“Shim under bucket” LOL…
SO…what I think you should do is REMOVE the shim entirely…then check clearance…making sure that when there is NO SHIM…it all goes together properly and doesnt rely on a shim to be there? Does that make sense?
So take the shim away…reassemble…measure your clearance…then measure your shim… Note the clearance you want…and subtract…then carefully slowly remove material in a UNIFORM manner from the shim…using a micrometer to make sure its even and accurate… Stop when you are close to your needed thickness…stop on the thick side… and re-measure
This isn’t over your head is it? Just checking my man… I’m here to help… Really wish you had EXTRA shims… Its all or nada with THE one and ONLY one you have… I’d feel better if I was there doing this for you…and or you had extra shims… They are available…dont worry
S A V V Y?
I had the auto parts store measure the disc and it’s 3.17mm thick. And there is a number on the disc:
3.244. Does this help any?
DO YOU WANT TO CALL ME? I WILL BE AVAILABLE TO HELP YOU IF YOU WANT !!!
CALL ME 6109454015 If you want man…
YES that is the thickness THATS the shim…
No. it doesn’t look like that. It looks like a computer battery or a large watch battery
TELL me…if you were to remove the shim entirely would the bucket go over the valve in an acceptable manner with no wobblyness to it…I mean would it just be like a micro thin shim… SOMETIMES you cant have no shim…
IF YOU CAN put it together without the shim then we are home free…
Measure clearance with NO shim… measure your valve lash…measure your shim…which we already know…factor in the valve lash…and subtract it from the shim…and alter your shim to give you the target lash… Do you understand? Did I say this correctly… I know what I mean…I just hope I’m saying it right …