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Old 11-06-2009, 04:29 PM   #1
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Default Valve clearances on a 99 head- Please check my math

Had a few questions about setting valve clearances on a 99-00 head. I found on m.net that the spec for setting the clearances is as follows:

IN: 0.18—0.24 mm {0.008—0.009 in}
EX: 0.28—0.34 mm {0.012—0.013 in}

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Currently my clearances for two are off, slightly.
1 inch= 25.4mm
Intake #1 is .015 inches which is .381mm- Has a 3.370mm shim in it
Intake #2 is .012 inches which is .3048mm- Has a 3.5mm shim in it

I would like it on the lower side of spec, right?

For # 1 ill want to add an additional .1778mm to my current shim to bring the clearance down to .008, right?

For # 2 ill want to add an additional .1018mm to the current shim to bring it down to .008, right?

Hows my math?

Also, wondering if the clearances should be any different since i have supertech valves and springs in the head.
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Old 11-07-2009, 12:04 AM   #2
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Since you're running stock cams, I'd be inclined to run stock clearances. Cam geometry is generally the bigger factor what clearances you run moreso than valves/springs.

Your math is close enough... I got the same thing on intake 1 and .1016mm on intake 2. So you'd want a 3.548mm shim on 1, and a 3.602 shim on 2.


Quote:
Originally Posted by thesnowboarder View Post
Had a few questions about setting valve clearances on a 99-00 head. I found on m.net that the spec for setting the clearances is as follows:

IN: 0.180.24 mm {0.0080.009 in}
EX: 0.280.34 mm {0.0120.013 in}

Sourch:
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Currently my clearances for two are off, slightly.
1 inch= 25.4mm
Intake #1 is .015 inches which is .381mm- Has a 3.370mm shim in it
Intake #2 is .012 inches which is .3048mm- Has a 3.5mm shim in it

I would like it on the lower side of spec, right?

For # 1 ill want to add an additional .1778mm to my current shim to bring the clearance down to .008, right?

For # 2 ill want to add an additional .1018mm to the current shim to bring it down to .008, right?

Hows my math?

Also, wondering if the clearances should be any different since i have supertech valves and springs in the head.
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Old 11-12-2009, 05:00 PM   #3
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Oh god...I remember doing this. 16 times. Makes simple math seem more complicated than it really is.
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Old 12-16-2009, 06:47 PM   #4
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My local dealership only has 3.4mm and smaller, where can i find a 3.5-3.6mm ?
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Old 12-16-2009, 08:31 PM   #5
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Quote:
Originally Posted by thesnowboarder View Post
My local dealership only has 3.4mm and smaller, where can i find a 3.5-3.6mm ?
3.396mm is the thickest shim listed in the parts catalog.



Perhaps the dish in the follower is sufficiently deep that you could place a thin piece of material (such as a piece of sheet metal you've cut out) under the shim? 'Course, I'd hate to see what happens if a shim gets ejected from the follower because you stuck something under it. There's nothing in the FSM which tells you what to do if the thickest available shim won't get you where you need to be.
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Old 12-16-2009, 08:47 PM   #6
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Quote:
Originally Posted by Joe Perez View Post
There's nothing in the FSM which tells you what to do if the thickest available shim won't get you where you need to be.
Find out why its so off. I personally think if its that far off that a head rebuild should be considered.
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Old 12-17-2009, 12:44 AM   #7
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Quote:
Originally Posted by thesnowboarder View Post
My local dealership only has 3.4mm and smaller, where can i find a 3.5-3.6mm ?
You may need to have your valves sunk (seats ground), or go with a longer valve.
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Old 12-17-2009, 11:49 AM   #8
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Quote:
Originally Posted by thesnowboarder View Post
I would like it on the lower side of spec, right?
Anyone have any input on this? Where do we want to be in the spec range?
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Old 12-17-2009, 12:21 PM   #9
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From a performance standpoint you want the thinnest shim possible in there to minimize mass.

In my experience you don't often have to do much adjustment once the head is past its initial settling in period after a rebuild, so I'd want to see it start at the mid-point of the shims available or smaller ideally.
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Old 12-17-2009, 01:49 PM   #10
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Originally Posted by MartinezA92 View Post
Find out why its so off. I personally think if its that far off that a head rebuild should be considered.
So, how does it get this loose?

Could be cam / follower wear, but I'd think you'd notice the metal shavings.

Valves generally don't get shorter over time. They stretch, but they don't contract.

Horrible foulness built up on the mating surface between the seat and the valve? Lapping would answer that...

I'm in the dark here as much as the OP. Last engine I had to adjust valves on was my '71 VW, and that thing was so random you'd think the valves really were growing and shrinking on their own. But instead of shims it used screw adjusters (like an American V8) so until you ran out of thread, there was no obvious min & max. And those adjusters were easily 1/2" long.

How, I wonder, are the cam journals holding up? Seems that if wear has occurred such that the cams are now loose-fitting in their bores, this would cause a general increase in lobe-to-follower clearance. Any fix for this short of milling down the seating area for the caps and then line-boring the cam holes? Never been down that road...


Quote:
Originally Posted by Rennkafer View Post
From a performance standpoint you want the thinnest shim possible in there to minimize mass.
Let the difference in mass between the thickest and thinnest shim be called X.

The mass of the valve, the follower, and the portion of the spring which is effectively unsprung is probably > 10,000 X.
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Old 12-17-2009, 02:03 PM   #11
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The motor was put together this way, if i were to yank the head would the proper adjustments be able to be made? I was under the impression the length of the valves was the determining factor for shim sizes. The valve clearances have not changed since the day i got the motor and the way it sits in front of my house. 200-300 miles since its first start.

If i can pull the head, adjust various things, throw a new head-gasket in, re set the valve clearances then i would love to do that. I would rather not invest more time and money into it if possible.

Quote:
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3.396mm is the thickest shim listed in the parts catalog.
This is what my dealership said as well. What boggles my mind is that i have a 3.5mm shim in the head now..
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Old 12-17-2009, 02:52 PM   #12
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Originally Posted by thesnowboarder View Post
If i can pull the head, adjust various things, throw a new head-gasket in, re set the valve clearances then i would love to do that. I would rather not invest more time and money into it if possible.
Yes, the valve clearance adjustment can be done with the head removed from the engine. You might need to jimmy up a mechanism to lock the cams in place if you find that they want to autorotate to a position that does not align the lobe bottom with the follower, but everything else will be fine.

While the head is off, you might as well pull the valves and spend some time lapping them into their seats with valve grinding compound. It requires some sweat equity, but it's not rocket science. At a minimum, this will improve the valve sealing a tad. If you're lucky, and there's currently a lot of crud at the valve-to-seat interface, it may allow the valves to retract more fully into the closed position, which will decrease the lobe-to-follower clearance and just might bring you back into spec for stock shims.



Quote:
What boggles my mind is that i have a 3.5mm shim in the head now..
Perhaps it was acquired from a source other than Mazda? It's quite possible that there's some other engine out there in the world which uses the same size shims, and for which greater thicknesses are available.
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Old 12-17-2009, 04:44 PM   #13
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i take it this is just for the 99-00 head? it be great if someone made a youtube video of the procedure and what to do.
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Old 12-17-2009, 04:51 PM   #14
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Snowboarder, You may be able to stack two shims. See if there are two shims from Mazda that will give you the height that you need. Make sure that you go on the tighter side of spec to prevent a skinny shim from jumping out, and put the thicker of the two on top.

If there are not two shims that will give you the spec that you need, you can grind one of them down without any special tools at home. See if there are skinny shims available, and I will show you how to grind them if one needs it.

It is a lot easier to do a valve job when the head is off the car. You will be taking the cam on and off many times, and it sucks when you are hunched over the fender all the time.
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Old 12-17-2009, 05:31 PM   #15
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I just looked at Joe Perez's diagram, and it looks like the smallest is 2.75. That would be a lot of grinding. I think I would lap the valve as Joe suggested. It would be faster than attempting to stack two shims and grind one down. You are so close, that valve laping should get you there. The only pitfall, is you will need to put the valve spring back on in order to get an accurate measurement.......If it is not enough that could mean: disassemble, grind, reassemble, check; disassemble, grind, reassemble, check.
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Old 12-17-2009, 06:33 PM   #16
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Quote:
Originally Posted by miata2fast
If there are not two shims that will give you the spec that you need, you can grind one of them down without any special tools at home.
As you observed, it'd be a lot of grinding. In order to prevent the upper shim from being raised up so far that it's ejected from the follower (the lip isn't very tall) you'd need the lower shim to be *really* thin. Like 0.3mm maybe. I doubt seriously that I could grind down a shim by that much and still have it be sufficiently flat. If I were going to attempt anything like this, I'd start with a piece of very thin sheet metal (28ga or so) and punch out an appropriately shaped shim from that.

Not that I'd feel particularly secure about doing it.

It's kind of like saying "If I were going to commit sodomy, I'd do it in the following way..."

Just sayin' is all.



Quote:
Originally Posted by miata2fast View Post
I think I would lap the valve as Joe suggested. (...) The only pitfall, is you will need to put the valve spring back on in order to get an accurate measurement.......If it is not enough that could mean: disassemble, grind, reassemble, check; disassemble, grind, reassemble, check.
Well, realistically I don't think you're going to remove a significant amount of metal doing it by hand. This is more of a polishing process than a cutting process. IOW, if the first pass doesn't get you there, and yet you see shiny metal all around the seat, I don't think additional lapping if going to do much. The idea is to treat this as low-hanging fruit; make sure there's absolutely no grime causing the valve not to retract fully, and then see if that buys you anything.

If you're still out of spec, I'd take the head (and the valves) to a machine shop and have them re-cut the valve seats by about 0.5mm or so.

And then, of course, you have to re-lap 'em again.


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Originally Posted by Hot_Wheels View Post
i take it this is just for the 99-00 head?
All NBs use the same shim-on-bucket follower design. So that'd be '99-'05. The NCs probably use a similar design, though I've never lifted the valve cover on one.


Quote:
it be great if someone made a youtube video of the procedure and what to do.
The procedure in the manual isn't hard to understand, though it does presume the use of a SST to depress the followers. I've heard of folks fabbing their own. You could also just take all the measurements, then remove the cams and drop in the new shims. Granted, if you screw up you gotta repeat the whole process.
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Old 12-17-2009, 07:01 PM   #17
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He is off by what, a tenth or two of a millimeter? I think that a coarse lapping compound could get him there. But you may be right. I would call a machinist that is skilled in valvetrain to see what they think.

Here is another possibility. If you can get your hands on other lifters, there are differences in how deep the shim cup is or how long the contact point from lifter to valvestem is. The machining is not as precise on them, and you will probably find one that will use a thinner shim and get you where you need to be.
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Old 12-17-2009, 07:31 PM   #18
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Originally Posted by miata2fast View Post
The machining is not as precise on them, and you will probably find one that will use a thinner shim and get you where you need to be.
That's a very interesting observation, and one I'd not considered. I've got a full set of '99 followers sitting on the shelf at home. If I get bored next week, I believe I shall mic 'em all and see what the variance is.
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Old 12-17-2009, 09:46 PM   #19
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Quote:
Originally Posted by Joe Perez View Post
So, how does it get this loose?

This is what I want to know. I would think the valves would move up, requiring smaller shims, just from seat to face wear. I skipped the posts but in case someone hasn't mentioned it, I would measure the shims with a mic and see if they aren't wearing away. I would expect metal shavings in the oil too, but you never know.

Only thing I see possible is build up like Joe Perez said. If you end up taking this head apart Nick, pics or ban.

Quote:
Originally Posted by Joe Perez View Post
You might need to jimmy up a mechanism to lock the cams in place if you find that they want to autorotate to a position that does not align the lobe bottom with the follower, but everything else will be fine.
I personally used a ratchet on the end of the cam and spun it. Just stuck a feeler gauge in each space. Wasn't too hard.

Quote:
Originally Posted by miata2fast View Post
I just looked at Joe Perez's diagram, and it looks like the smallest is 2.75. That would be a lot of grinding.
I actually tried this just for ***** and giggles because I hadn't found cheap enough shims yet. Local dealer was asking 20 a piece. F-dat.

In my experience it took ages. And would be very hard to get exact. Shims are made of pretty hard material.

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Originally Posted by miata2fast View Post
The only pitfall, is you will need to put the valve spring back on in order to get an accurate measurement
If you could get your hands on a tool to measure installed stem height, you could just push the valve up with your hand and do some simple math. I don't remember the spec for this off the top of my head, but theres a small shim which is .020" that is under the spring which you would have to put in place because it is included in the measurement.

Last edited by MartinezA92; 12-17-2009 at 09:58 PM.
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Old 12-17-2009, 11:47 PM   #20
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Several things...

1) Nicks head came to him from the engine builder this way... the valves were improperly machined. The right thing to do is take the head off, take it back to the builder and say "fix this".

2) You can't accurately grind the shims without a surface grinder, and they need to be flat. You simply can't keep them flat enough hand grinding.

3) I'd be suprised if there's enough variance in the lifters to be helpful, but it would be interesting to see Joes measurements... I have a set of 99 lifters out of a head at the moment I'll measure when I get a chance as well.
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