Problem with Viton valve seals

[Zmanco]

After reading the sticky on the alternate Felpro seals SS72686 http://forums.hybridz.org/showthread.php?t=90825 I decided to use them on my P90 head rebuild. The machine shop just called and said that they have a problem with the seals. As he described it, as soon as they push down on the valve, the seal's spring pops off. He thinks they are for a smaller diameter valve stem.

 

The shop is pretty far from me so I haven't gone over to see it for myself yet. Any suggestions? I'd rather not go with the stock seals, although I guess I could as I've been running this reground cam on another head with stock seals with no problem. But I liked what I read in the thread about the better longevity of the Viton seals, and on top of that, they were cheaper too.

 

Thoughts and suggestions?

[Zmanco]

Looks like Felpro has a set that is specific to the L6 part # SS27415.

 

http://www.autozone.com/R,APP21617/vehicleId,1218502/initialAction,partProductDetail/store,834/partType,00013/shopping/partProductDetail.htm

 

The picture is too small to tell what the material is. Does anyone know if it's Viton?

[JMortensen]

After reading the sticky on the alternate Felpro seals SS72686 http://forums.hybridz.org/showthread.php?t=90825 I decided to use them on my P90 head rebuild. The machine shop just called and said that they have a problem with the seals. As he described it, as soon as they push down on the valve, the seal's spring pops off. He thinks they are for a smaller diameter valve stem.

 

The shop is pretty far from me so I haven't gone over to see it for myself yet. Any suggestions? I'd rather not go with the stock seals, although I guess I could as I've been running this reground cam on another head with stock seals with no problem. But I liked what I read in the thread about the better longevity of the Viton seals, and on top of that, they were cheaper too.

 

Thoughts and suggestions?

Based on the other descriptions in the thread you linked to, it sounds like the machine shop is pushing the seals too far down on the guide. The L series seals are going to be L series seals, and won't give extra clearance for a larger cam.

[BRAAP]

The Felpro VITON stem seals were not designed for the L-series, but for Ford V-6 engines. They will work on the L-series and are desirable as they are shorter allowing more retainer to seal clearance, the Viton material is much more resilient and a longer lasting material vs the OE specified seals which generally a Poly Carbonate that becomes brittle over time. When installing the Viton seals, extreme patience and care is required. I’ve installed literally hundreds of those stem seal on L-series heads and learned the hardway, i.e. more than few sets of stem seals trashed during the learning curve. Here is my current procedure for installing these seals.

 

 

1) Always use the stem seal condoms over the valve stem to protect the seal from being cut as it passes over the keeper groove. For the L-series, I always cut those stem condoms down to half their length.

 

2) The top of the guide AND the inside of the stem seal need a thin film of oil.

 

3) “Carefully and gently” ease the seal down the valve stem till it contacts the valve guide. Now with even more care and precision, and bare hands, grab the metal perimeter of the seal and spin it while pushing against the guide. This will help just start the seal over the guide. This is not a 100% guarantee it will go one without any issues but it does reduce the tendency of the inner rubber to tear and bunch up on top of the guide as it is being installed. Trust me on this!!!

 

4) Now that you have the seal started on the guide, using your seal installer, (bare hands will NOT push these seals on all the way) the normal tendency is to push them on all the way! Resist that temptation with all your might as the Datsun guides will bulge the top of these seals out, sometimes off to one side leaving a gaping hole between the seal and the valve stem for oil to drain down the guide an into the port and this is also when those springs pop off.

 

5) Some of these seals are green, some are black, (no idea why the difference, its just what I’ve seen in all the ones I’ve installed, all the same part number). If you notice that the green or black portion has been overly stretched, evidenced by the white stretch marks near the metal shield surrounding the seal, the seal is no longer any good and needs to be replaced.

 

6) When installing these seals, it is imperative you have an extra set on hand as it is inevitable one or two will get boogered up during install. Some times I can build 5 heads with not one issue, then I can build up 2 heads in a row and end up trashing a couple seals per head.

 

7) Again, scrutinize the installation of these seals very carefully as they are very finicky and easy to screw up.

 

 

For mild lift cams on engines that wont see more than 100,000 miles, the poly carbonate seals are a no brainer choice, in my opinion.

 

 

 

Here are a couple pics of this seal improperly installed, spring has popped off…

 

This pic below shows the bulging of the green rubber from being installed to far;

 

 

 

This pic below shows the gap surrounding the valve stem as a result of the bulging from being installed to far down, i.e. there is more clearance between the valve stem and seal than there is between the valve stem and the valve guide itself!!! You can make out the top of the guide through that gap!!! Oil burner for sure!!!

 

[Zmanco]

Based on the other descriptions in the thread you linked to, it sounds like the machine shop is pushing the seals too far down on the guide.

That's what I'm thinking is going on. I guess I'll have to drive over there tomorrow to see first hand.

 

BTW, in re-reading some posts on shaving the P90 head 0.080", it's not clear if it's necessary to put shims under the valve springs. I'm planning to use the earlier (longer) valves to hopefully not need to change lash pads. Given that Nissan uses the same spring for both valves, is it desirable and/or necessary to shim up the valves? Obviously I need to get this figured out before going any further with valve seals.

[Zmanco]

Paul, as always, thank you for the very detailed advice for the installation. A few clarifications if you don't mind:

 

- any chance you have a picture of the condom? Many have suggested using them, but I haven't seen a source for them nor even have a clear picture of what they look like.

 

- The process you describe sounds like the seals can easily be damaged. Is this just for the Ford seals, or the polycarbonate as well? The shop that did the machine work wants to reinstall the valves in order to warrant their work. I'm inclined to let them do it unless the L engines are different enough in which case I'll just do it myself.

[BRAAP]

Daniel,

You are quite welcome.

 

1) Pictures of the condoms below. Full length and cut down. (Found a spare good condition Viton stem seal for the photo shoot…)

 

2) Yes, the Felpro Viton seals can easily be damaged. The Felpro, or any other OE replacement stem seal is a no-brainer to install and any shop/grunt can safely install them without issue.

 

 

First pic is of the condoms and also shows a normal Viton seal, i.e. NO bulge and spring is intact…

 

 

 

This pic shows the FelPro Poly Carbonate and the Viton seal side by side. You can clearly see the height difference.

 

[Zmanco]

Pictures are great! Now it's clear to me. BTW, looks like the condoms are provided in the Felpro kit. I'll have to go visit the shop today and see what we can do. If he's already buggered the Viton seals, I'll probably just put a set of the polycarbonate Felpros on it and call it a day.

 

Again, thanks for all the advice and education. I agree, it's important (and fun) to keep learning. Besides driving it, I think the best part of having an early Z for me has been learning about all the subtle issues involved in building something that is better than stock, and yet is still reliable.

[dapiper]

STI makes viton seals in stock size and config.