Teflon seals and valve stem wear

Nothing ?

The Teflon seals are very tight on the KW stems and that includes with the coil removed so will use the seals in the AN gasket set and hope they stay on the guide.

Well , anything has to be better than the plastic type original type valve seals. Mine were running hard as a rock and riding up and down the valve stems causing hydraulicking effect of gathering up oil and pushing down into the guides. Smokey. Bought Kibblewhite seals and Black Diamond vales and fitted and all good to go. Guides weren't at all worn due to the excessive lubrication. I wonder how many owners rebore to oversize on realizing the smokings fun ,when they should pay more attention to head seals issues. I ran teflon seals on my (street-driven) 340S Barracuda and put over 100k miles on that engine. No issues with abnormal valve wear. Although I can't say for sure, based on what I've seen from observation, I suspect that there is more oil being deposited on the Norton valve stem than there was on the 340 valve stems. So I can't imagine there would be a problem with the Norton unless the valves themselves are of marginal quality. I pulled a set of old teflon seals out of a US-sourced Combat head I was refurbishing a few years back. I don't know how many miles they had done, but I elected to refit them rather than the neoprene (?) OEM type I had lined up for the job. I rather liked them.
I've never seen them in the UK, but I don't get out much... If using stock type seals you should at least get the ones with the springs on them. Better yet the Viton seals from Kibblewhite or summit racing. The teflon seals should be reserved for rare occasions when using a total seal gapless top ring (instead of a gapless 2nd ring) because a gapless top ring creates extra vacuum and can pull too much oil through the guide. On one motor, I'm running the red Kibblewhite spring-less seals (style 1) on KW bronze guides and black diamond valves. Hope they stay on over time. They go on a bit too easy. Will inspect and probably switch for the spring seals the next time I have it apart.

Fullauto head on my 74 off and it had the red KBW seals, style 1. They are 8 years old and 10k on them. Still completely flexible. The stems on one of the KBW valve show almost no wear the other more but still serviceable. It never burned oil until the rings took a hit.

On one motor, I'm running the red Kibblewhite spring-less seals (style 1) on KW bronze guides and black diamond valves. Hope they stay on over time. They go on a bit too easy. Will inspect and probably switch for the spring seals the next time I have it apart.

I run style 1 . No issues , but will try style 2 next time head is off as they did go on a little too easy by hand.

I had Style 6, considered using them once again then binned them.
It has the stock no spring OEM seals now, if it smokes I will simply pull the engine out and replace them with Viton.

But....which style Vinton would you use? Style 2 seems like it might be the way to go to me, but I don't have first hand experience with either. Cj

But....which style Vinton would you use? Style 2 seems like it might be the way to go to me, but I don't have first hand experience with either. Cj

I never knew there was that multiple choice.

They were so tight (# 6 ) you could hardly move them on the stems (even with the spring removed), it didn't even distort when I used it as a valve protector and still left a mark.

I think I will go Style 2 in the future. In the automotive world, it is fairly well-known that the white teflon PC seal usually gets damaged when you pull out the valve and then the seal needs to be replaced.

Not a big deal because seals are cheap but it does add some time to remove and replace.

The red Viton seals are softer material so you can probably reuse them if you need to remove the valves.

I've had valves out twice last year!

So, I found the valve guides in my slant six are a bit too tall for the cam lift I plan to run. Time to take the head to a machine shop and get a bit of machine work done. Now the question I have: If I'm having the valve guides machined anyway, does it make sense to change them to run positive valve stem seals instead of the stock umbrella type? Pros and cons?

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The 340 springs I'm running have plenty of room to clear stock umbrella type seals, so interference with the valve spring is not a limiting factor.

Yes, go positive  seal. Preferably a Viton material.

Pros over an umbrella are: Higher quality material, less likely to create a "pumping" of oil into the guide, won't flop around and get cut/fail, controls oil much better, longer lasting, more clearance to spring.

Cons: extra costs but not much

On applications where more oil is preferred to get into the guide such as circle track (high rpm, or endurance) just remove the spring from the seal to increase the oil flow. In extreme cases I don't run a seal at all on the exhaust.

IMO the only reason to keep using umbrella seals is because you don't want to pull the head off and send it out to be machined.  They "work" but this is , we can do a lot better if you are willing to have the machine work done.

And yes, Viton.  The cheesy white nylon seals belong nowhere near a functional engine.

In reply to MadScientistMatt :

Contact us to discuss your requirements of viton valve stem seal. Our experienced sales team can help you identify the options that best suit your needs.

Only time I ever ran into a seal not holding the guide properly was a bad machine because of loose guide clearance (it wobbled around and caused the tool to cut small), trying to set the size with the incorrect tool, and lastly cheap/ or miss machined replacement guide. 

In your case the machinist will have a STD fixed tool seal cutter. Your guides should be in good shape since its apart check them, if not, get the full valve job done.

In reply to MadScientistMatt :

Engine Machine shop should have them in bulk. Its all pretty standard sizing and minimum variations. Yours is likely 11/32 valve stem and if a .500 seal cutter is used that would be a US Seal VS-107 or VS-108. If a .530 seal cutter is used it'll be a VS-530. Different brands vary in part number and minimal OD size. As long as you ask for/make sure its a metal clad/body type like the VS-107 and VS-108 here: https://ussealparts.com/cylinder-head-parts/valve-stem-seals.html?guide_size=23&material=9&packs=497&stem_size=12&style=4&style_type=35

On my Datsun the motor sees between 4K-8K and is rarely below RPM, I used both types of seals and haven't noticed a difference either way.  With that said I'd go with the positives seals if you're already having the work done.

asphalt_gundam said:

In reply to MadScientistMatt :

Engine Machine shop should have them in bulk. Its all pretty standard sizing and minimum variations. Yours is likely 11/32 valve stem and if a .500 seal cutter is used that would be a US Seal VS-107 or VS-108. If a .530 seal cutter is used it'll be a VS-530. Different brands vary in part number and minimal OD size. As long as you ask for/make sure its a metal clad/body type like the VS-107 and VS-108 here: https://ussealparts.com/cylinder-head-parts/valve-stem-seals.html?guide_size=23&material=9&packs=497&stem_size=12&style=4&style_type=35

Thanks - I had been expecting to track down the parts myself, but if I can just bring the head and valves to the machine shop, and the seals are only a few dollars on their own, this sounds like it should be pretty easy.

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