I've got a brand new set of Supertechs from Fab9 (1 month ago) and a brand new set of the "Supermiata" seals (yesterday). I'm going to take careful measurements of some key surfaces and see if I can discern anything.

OK I've finally got some solid information. I have brand spanking new sets of BOTH the Supermiata seals (Felpro?) and a set from Fab9 (the Supertechs).

The results are very obvious. Using a set of gage pins to inspect diameters:
The Supertechs are .010" larger in every dimension.

Description of measurements:
"Inside diameter" is the largest gage pin that fits with nearly zero friction
"Easy to slide" is the gage pin size that fits (with oil) and is "easy to slide" up and down. Very subjective, but I think informative
"Larger inside diameter" is the second lip that fits over the valve guide.

Those Supertechs don't belong on this car. I put the Supertech on the valve stem and you can axially move the body and see daylight between the stem and the seal. NO BUENO. The Supermiatas fit nicely and don't have any play.

For once, bigger is NOT better! Someone tell my wife!!

And Fab9 - You really must stop selling these things.

Fudge i got my head rebuilt with those...

And one more very valuable piece of information. You should install the seals and then install the valves ONCE. The valve stem has a very sharp tail edge that shreds the valve guide inner surface when you pull the stem out of the seal. When pushing the valve in it is OK, it is when you remove the valve that it catches the seal rubber and can damage it.

So if you think you will install the seals, the install the valves (and everything else), then check your lash, pull out the valves and grind the stem length down and re-install - BAD. You just damaged those new Supermiata seals. Ask how I just found out...

Of note - the Supertech seals DO NOT get damaged when pulling on and off the stem, because they are too big anyway!

I'm probably going to grind that sharp edge off of my stems so I don't damage the seals ever.

Props for the measurements.

Would you be willing to measure the Miataroadster seals if I had an order shipped to you? My engine is going in next month and I'd like to see the measurements for those while I still have the engine out.

MR-VVSS-16 - MiataRoadster Viton valve stem seals - MiataRoadster - High-performance service...and parts for Mazda Miata Roadsters

So just for clarrification, 949Racing states their valve seals come from the, "Same supplier as Mahle, Clevite, Fel-Pro, others," but are Viton instead of rubber (like OEM and Fel-Pro SS72802 replacement valve seals)

If plenty of folks are having successes with good old fashioned rubber OEM/Fel-Pro, why is the push for Viton? Will it actually last longer or is there still a game of getting the tolerances just right before one see's any benefit at all.

Here's a good article on valve guides & seals, Valve Stem Seals Materials and Designs . After following all the 'troubles' of the Supertech seals the common factor seems to be a lack of information about stem to guide runout or real world valve guide wear and ovality. I had my head rebuilt by a local builder who checked the valve guide diameters vs the valve stems with bore gauges while going through the process. He said they were within the Mazda tech spec [it was a fairly low mileage head] so I had him use the Supertech seals as 1. I had them on hand and 2. It's what he uses generally. During our conversations he also showed me how to install them using the 'straw method' so the seals don't get cut.

Another PDF file from SKF on the subject of valve guide seals with some relevant information, Valve stem seals - SKF

Unfortunately, the engines still on the stand waiting for warmer weather. I've thought of pulling the head off and replacing the seals but likely will not.

Looking at the dimensional information that Mudflap measured, both mfg seals are well under the minimum stem diameter. A question would be "what's appropriate"? There's supposed to be a certain amount of oil on the stems as they go into the guides to keep wear down. Reading through different material says there's as much into the contour of the seal lip that determines how much oil is metered than plain dimensional attributes.

https://cimg2.ibsrv.net/gimg/www.mia...7b5997117a.jpg
https://cimg1.ibsrv.net/gimg/www.mia...d79455bca0.jpg
https://cimg9.ibsrv.net/gimg/www.mia...2372c463b0.jpg

Thanks for the information. I've run into the case where my car puffs from dead stops or long idles with the head having had all valve guides replaced using Supertech. This table pre-emptively answered my questions about the difference in valve stem diameters between stock and advertised values given by Supertech, however, I can only offer anecdotal gripes from a performance shop that built my latest head/shelf ornament said they had nothing but trouble using Supertech components. The valve lengths would sometimes not be as advertised and raised general QC issues with supertech products in general.

At this rate, I'm just curious whether or not to move forward with the Supermiata Viton or run of the mill Fel-Pro rubber (which has many documented successes).

I'm not at all familiar with what Supertech actually manufacturers themselves [if anything] vs source. I doubt they produce their own seals given the wholesale selling price. Maybe one of the site vendors has more information.

Mudflap and I have been PM'ing a bit back and forth. I had a new seal set sent to him from MiataRoadster, the inside diameter measurement was provided - hopefully he can fill in the missing measurements.

Supertech Valve Seals (Viton) - Supertech Valve Seals for Mazda Miata
Inside Diameter .202
Easy to slide .215
Larger inside diameter .270

Supermiata Valve Seals (Viton) - https://supermiata.com/Supermiata--v...s-miata-1.aspx (Same supplier as Mahle, Clevite, Fel-Pro, others.) - does not imply same material.
Inside Diameter .191
Easy to slide .207
Larger inside diameter .260

MiataRoadster (Viton) - MR-VVSS-16 - MiataRoadster Viton valve stem seals - MiataRoadster - High-performance service...and parts for Mazda Miata Roadsters
Inside Diameter .198
Easy to slide .xxx
Larger inside diameter .xxx

I'm not sure we have the FelPro or OEM measurements.

I'm installing an engine this weekend and will have it running shortly thereafter - I'll update on the MiataRoadster seals once I have a few miles on the car.

I just hope it's not smoking up a storm while tuning

Meh, what's another couple of weeks of downtime?

OK, so although Summit Racing lists the material for Fel Pro valve stem seals as Rubber, Autozone (of all places) references it as FKM which is another word for Fluoroelastomer containing the same monomer as what is consistant with DuPont's trade name Viton.

Solid work

OK folks I've got three brands in my hands now. I wish I still had the OEMs (thrown away).

The measurements betwixt the three clearly show that the Supermiata (Felpro I believe) are superior. But the bottom line is the fit on the valve stem. All three require a little pushing to get them onto the valve stem. But the Supermiata takes more push than the other two. If you lightly push the seal body against the valve stem you can easily detect light between the valve stem and seal. Not so on the Supermiata.

It is too difficult to tell which ones slide up and down more readily. The problem is, once stopped, they require a minimum force to break the tension to get them moving. That force is too difficult for me to measure in any meaningful way.


Supertech Valve Seals (Viton) - Supertech Valve Seals for Mazda Miata
Inside Diameter .202
Very easy to push against the stem to see daylight (moon shaped gap).

MiataRoadster (Viton) - MR-VVSS-16 - MiataRoadster Viton valve stem seals - MiataRoadster - High-performance service...and parts for Mazda Miata Roadsters
Inside Diameter .198
Easy to push against the stem to see daylight (moon shaped gap).

Supermiata Valve Seals (Viton) - https://supermiata.com/Supermiata--v...s-miata-1.aspx (Same supplier as Mahle, Clevite, Fel-Pro, others.) - does not imply same material.
Inside Diameter .191
Requires more force to push against the stem to see daylight (thin gap).

Do you have the felpro ones to compare with as well? Curious how the Supermiata ones look compared to those. Or do we expect them to be exactly the same? Same supplier doesn't necessarily mean same spec right? I know you pointed out that it didn't necessarily mean that the material doesn't have to be the same either.

If anyone out there has a positively identified OEM and/or Felpro I'd be happy to do a direct comparison and report.

I'll have this head apart for at least a few more weeks. Hopefully not longer!