Well shit.


(Much more recent CNC owner, getting installed [again] soon).

@dleavitt, are you smoking/leaking past the seals?

Short version: maybe.

Slightly longer version: Had my head installed by a competent shop back in January. After a few starts at the shop (still waiting for other parts) much smoke appeared. Shop suspected valve seals, but Emilio INSISTED that it was the rings in my 150k block. At the time I said to myself: "You know, Emilio is probably right. Besides, what are the odds of all of the valve seals being bad in a brand new head?"

While I waited for my block to be completed, this thread pops up with basically everyone saying Supertech seals are full of fail and AIDS. :facepalm:

Car is getting put back together as we speak, so we'll see what happens.

We should know soon enough, curly is putting the motor back together at our shop.

My Mahle one's don't seem to be leaking. I've just had the car idling though.

I swapped out new Supertech valve stem seals for some 949 racing valve stem seals. We will see if they leak or not.

https://c1.staticflickr.com/5/4287/3...2ec17295_b.jpg

https://c1.staticflickr.com/5/4220/3...be9ab827_b.jpg
https://c1.staticflickr.com/5/4249/3...2793361a_b.jpg

Cheater, you took the head off.

haha the head hadn't even been installed yet, which made it that much easier for me. Now I just have to keep my fingers crossed that these will not leak. Who knows maybe the Supertechs I had originally installed at the machine shop wouldn't have leaked either.

Much smoke = not valve seals.

Brand new CNC head on 150k old bottom end = much smoke

Any news on the Fel-Pro seals?
Anyone use them? Any leaks?

I'd been following this thread thinking to myself... maybe intake contamination. Then I see that many of you have the valve cover vented to a catch tank; separated from the intake. Then I'm thinking... probably worn guides... Now I'm seeing at least a couple of you are using new guides. If it is the valve stem seal then I wonder if there's a way to bench test it?

I remember that once I had an oil leak in a new build (it was near the rear main seal). Differential diagnosis was rear main seal vs input shaft seal on trans. (both using synthetic so hard to tell by smell) The folks at Jerico (trans manufacturer) told me to pressurize the trans case and look for seepage. It worked beautifully and the problem was found. Could this be applied to the stem seals? Could you apply a little positive pressure from above and demonstrate leakage?

Shame on you for wanting to use scientific methods! Hearsay, innuendo and accusations are the order of the day here.

Seriously, this is a great idea. What pressures does a stock engine generate in the valve cover area? How about a 10-12 PSI tracked car? What pressure point should the seals hold to under typical conditions?

I'm using the 949 "Same supplier as Mahle, Clevite, Fel-Pro, others" seals. I'll have had them installed for a couple weeks now, and I'll been driving the car through the end of the week and then pulling the exhaust manifold some time this weekend. So while this won't be a long term durability thing, and I'm driving the car N/A at the moment, my STs died on the way home from breaking in the engine when it was first installed so I'll be able to at least tell you if they lasted longer than my STs :giggle:

You are talking about adding positive pressure to the entire crankcase in order to test the crankcase-to-port-past-the-valve-guide sealing ability. Lots of places to loose pressure that are lower paths of resistance than the valve guide/stem seal.

Are you talking about intake valve stem seals or exhaust valve stem seals? N/A application the intake stem seals are **always exposed to vacuum from the intake port and the exhaust valve stems seals are **always exposed to backpressure from the exhaust port. Add boost and now you've got pressure and vacuum on the intake and even more backpressure on the exhaust side. It would be fairly easy to pressurize the ports with the valves closed, but I very much doubt that would be a good enough seal to accomplish any meaningful testing with the head on the block.

** Yes, I understand how the ram air effect works on the intakes and scavenging works on the exhaust, but if you think for one moment this tractor motor of a BP has perfectly tuned intake and exhaust systems, you've got another things coming.

I'm thinking that you could squirt a little oil over the valve stem and seal ( springs removed), then press a piece of 1/2" hose over the stem and simply blow into it.

We never had massive issues or premature failures with the ST seals. We just noticed some minor leakage after long term inspection. We noticed engines run about the same usage with OEM seals had less or zero leakage. We installed OEM seals and seals from a few other manufacturers in various engines starting about three years ago. Over that time we noticed which seals leaked the least or not at all. OEM Mazda seals are perfect, just silly expensive. The alternatives we offer work just as well and cost a fraction as much.

So the process to determine which seals would be an improvement began long ago. We wanted to have long term data before making the switch from the ST seal to seals we offer now.

I have had them in my car. They're what I used when my ST seals leaked. I want to say since 2015. I have several autox and drag strip runs on them, no leaks. I catch a whiff of oil sometimes on decel after heavy boost, but my 2871 churbo is blowing some oil, so I think that may be the cause. Not using any oil at all and no evidence of leakage last time I checked. I don't want to stick words in his mouth, but I think Pat is using them with success too.

My Mahle seals are holding up well, no issues thus far. I'm thinking my rings might be tired however. I put a catch can in my car and have yet to see any more blue smoke under boost.

Insanely glad I found this thread today as I was about to purchase a set of ST seals for my wife's Miata. I still need to diagnose why it's consuming so much oil naturally-aspirated but figured this would be a good place to start. I plan on ordering the Fel-Pro kit.

141k miles, '99.

We have had the same experience as Emilio. We were buying FelPro rebuild gasket kits for our new engine builds, but using ST Viton valve seals. After noticing leakage down the stems after 10-20 hours of race running, we started just using the FelPro seals in the kits instead. No problems since. We have had a couple of engines come back that were due for new valve springs, and the seals still seemed ok.

I had originally installed ST valve stem seals on my freshly built head, but took them out and put in the seals 949 racing sells which I think are the same as Fel Pro. I have about 750 miles on the engine and so far there is no leaks that I can see, also car does not smoke.