I bought everything from Supertech to decorate the "upstairs". That includes the springs, as well.

Now, the truly interesting news...

I spoke with the guy who ported my cylinder head. He is a pretty cutting edge guy.
He tells me he has seen this happen way too many times with Supertech valves, and they simply erode away at the "angles".
According to him, cavities occur at the cut faces where they contact the valve seats, and he tells me has lots of pics to that effect.
He told me to get rid of the valves ASAP, and get different valves in there.

My question is, has anyone heard of or experienced premature wear on ST valves?
I was told I would just set myself up for another round of valve troubles if I repair this problem and continue using ST valves.

For the record, I have the following:

* Intake valves, Supertech brand, Part# MAIVN 1204

* Exhaust valves, Supertech brand, Part# MAEVN 1204

* Valve spring set, Supertech brand, Part# SPRK-MM18S (Springs, with retainers and seats)

I am running max 12-14 psi boost these days. The engine has seen about 18.5 psi last summer, when I was trying a much bigger pulley.
I also zinged the engine once on the track, and my maxi gauge tells me it went up to about 8250 RPM briefly when I was downshifting to 4th in panic, with a guy fishtailing in front of me at the end of a fast straight.

The car never overheated, not even once. Coolant stays below 110C, so does the oil. Those temps are actually at the 80-90C level most of the time. I do have a very good DIY reroute.

Any thoughts?

Most of that is taxes, the goverment there raised taxes on everything and laid off a bunch of employees in order to get bail out loans by the EU about a year or two ago.
Tough economic conditions for the average people.

Whoever cut your seats cut them too thin. I've run lots of ST valves and worked with a lot of motors with ST valves inside them, and there's no issue with the valves.

Does this mean the seats are wearing down?

In that case, that's a relief.

A valve relief?

A relief valve?

Sorry. I was required to insert a pun there due to my OCD.

More like a relief cut.

If there isn't enough surface area where the valve contacts the seat, the valve isn't cooled enough and can wear prematurely. The valve is cooled by its contact with the seat.

Does this mean you see a set of new valves in my near future?
I was really hoping I could save the valves.

The reason behind this hope is the fact that the engine runs well when it is warm.
If the valves were toast, they would fail to seal at all times, right?

I guess we'll know when I pull the head.

The valves and/or seats may need to be reground. This is a common procedure for a machine shop to perform. The angles chosen and the widths of the surfaces at each of the angles when finished can be different.

https://www.miataturbo.net/attachmen...ine=1419269933

https://www.miataturbo.net/attachmen...ine=1419269933

https://www.miataturbo.net/attachmen...ine=1419269933

https://www.miataturbo.net/attachmen...ine=1419269933

https://www.miataturbo.net/attachmen...ine=1419269933

https://www.miataturbo.net/attachmen...ine=1419269933

This is exactly why I found a decent machine shop and received the price quotes.

On the other hand, Supertech was very cool and responded to email immediately.

Here's their response, together with my initial email:



Hi there,

I have a 1998 Mazda MX-5 (identical to a '99 Miata), and the engine has about 17K miles since the rebuild.
(It was "built"as a precaution, not because of failure)

I used all Supertech components in the valvetrain:
* Intake valves, Supertech Part# MAIVN 1204

* Exhaust valves, Supertech Part# MAEVN 1204

* Valve spring set, Supertech Part# SPRK-MM18S (with retainers and seats)

After developing a severe cold miss, I checked the valve lash. 14 out of 16 valves are too tight, with the rearmost intake valve at "negative lash", meaning the cam lobe is pressing on the valve at all times, regardless of position.

Have you heard of any problems like this where the valve adjustment gets out of spec to the point of crossing over to "negative lash"?

I am in the process of pulling the head to lap (or replace, if necessary) the valves. Should I be worried they may wear once again in the near future?

For the record, the car is supercharged, with 10-12 psi boost. Engine coolant and oil temps never go hot, in fact they stay in the 80 to 90C range, with the oil occasionally going up to about 100C.

Please understand that I am NOT trying to get something from you. It's just information I am after.

Any information or ideas you'd be willing to share with me will be greatly appreciated.

Thank you,


------------------------------

Hi Hakan,
If when you put the new valves you also machined the seat inserts on the head, there are sometimes when the valves may have to adjust to the new machined seat and it will change the lash, so you will need a re-adjustment of the lash. But this will happen only once.

So you will need to adjust the lash and check sometime later to see if there any further change. There shouldn’t be.

Let me know any questions.

Best regards.
Willy Tagliavini
Supertech Performance Inc.
3550 Charter Park Dr., San Jose, CA 95136

------------------------

(Paraphrasing my response)

Does this mean I do not have to pull the head, then?

I mean, I was fully prepared to do that.


-------------------------

Hi Hakan,
No problem.

At this time you don’t need to pull the head away. Re-adjust the lash and check them after a race of several hundred miles if you only drive it on the street. This is most probably what happened to you.

If you still have problems, it would be very rare, but then you will need to remove the head to investigate more the reason.

Best regards.



I guess I'll give adjustment a try...

I disagree with Willy. When valve clearances tighten up slightly on a new engine, it's a normal thing, but normal is losing .002-.003", not the entire clearance (.011+). If you lose all the clearance, something is damaged, and resetting the clearance is not going to solve the problem. You'll be back inside the motor shortly (like in another thousand miles or less).

The engine runs fine when it's warm because the aluminum cylinder head expands faster than the valve does, which slightly increases lash clearance and allows the valve to make contact with the head again.

tl;dr: pull your cylinder head and replace your damaged valves, then find a machinist who is willing to cut a seat wide enough to prevent this from happening again.

We've list of all the OEM shims posted here, they're like $3.50 a pop from mazda.

Post a link to $3.50 Mazda shims?

Cheapest I can find them is $8.00 each, which is $0.80 cheaper than Rosenthal.

Machine shops do not necessarily use replacement shims.
They sometimes grind minute amounts off the tips of the valves to get the clearance correct.
Would you guys be opposed to this sort of procedure?

Here's a frame grab from a cheap scope I got a hold of:

https://www.miataturbo.net/attachmen...ine=1419803579

Looks like the seat is toast.
What do you guys think?

I am uploading the video to Youtube as we speak. I will post that video as soon as it is ready.

Still waiting for the gasket set. There is no point in tearing the engine apart without parts on hand.

Yeah, that seat surface looks like the moon.

Actually looks to me like carbon build up, and the good news is that it looks like the seat is not moving on the head itself, you can probably get by re grinding the seat and valve and re gapping valve lash

Yeah, but why would it miss cold, then be okay warm?

It is not ok when warm, it is just not as bad...