Should I Have Exhaust Valve Seals Installed?

[sixnboost]

I am having my heads rebuilt and I am wanting some opinions on doing the exhaust valve stem seals. Do I need them? Are they recommended? Is it worth the $$?

Thanks Billy

 

[Squid4life]

I used to work at a machine shop and anyone that didn't get exhaust seals usually came back complaining of smoke out the tailpipe. If it were me I'd do intake and exhaust seals, and get the good ones that last. I've seen stock "umbrella" seals ride the top of the valve instead of staying on top of the guide like they are supposed to. Worth the extra $ to me.

 

[ThikStik]

Some on this site have said that they can cause the exh valve to starve for oil and stay unseated thereby hitting the piston. Ive got them and may take them off.

 

[buickboy]

Valve guide boss is not machined for seals. Factory left them off, and so did i.
Mitch

 

[gofstbuick]

Originally posted by buickboy
Valve guide boss is not machined for seals. Factory left them off, and so did i.
Mitch

What he said. Why would you try to second guess a factory procedure? If the guide clearances are correct it really shouldn't have any type of leak condition. Additionally, that valve is not subject to the same conditions as an intake valve. The factory exhaust valve is not manufactured to accept a seal.

 

[KendallF]

Originally posted by gofstbuick
What he said. Why would you try to second guess a factory procedure?

Because they did it to save a buck?

[/i]
If the guide clearances are correct it really shouldn't have any type of leak condition. Additionally, that valve is not subject to the same conditions as an intake valve. The factory exhaust valve is not manufactured to accept a seal.

The factory exhaust valve will accept a seal just fine. It is machined with a notch that was the factory's low buck method of keeping excess oil from running down the stem. If you change to aftermarket exhaust valves, they will require a seal as they're not made this way.

The exhaust guide boss is not machined for a seal from the factory, and adding them requires cutting the boss down for either the factory style viton seals or smaller teflon seals. This is not an expensive procedure and usually remedies oil puff on startup problems.

If you want to ensure that the exhaust valve stem receives a bit of oil, run a slightly larger drill bit through the exhaust seals to allow this.

 

[sixnboost]

I am using Ferrea valves on these heads, so I probably should use valve stem seals it seems.

Does anyone have a brand and P/N that should be used?

Thanks again

Billy

 

[FastRegalWE2]

Originally posted by gofstbuick
What he said. Why would you try to second guess a factory procedure? If the guide clearances are correct it really shouldn't have any type of leak condition. Additionally, that valve is not subject to the same conditions as an intake valve. The factory exhaust valve is not manufactured to accept a seal.

What they said, I left them off too

 

[bruce]

Some alledged machine shops will try knurling the guides to tighten them up. While it works somewhat intially, shortly there after they loosen up some, if you don't have seals on the exhausts they'll let the engine puff on start up.

Too loose of valves with no seals will puff.

Properly done, ie no excesive play in the valve to head, it shouldn't puff.

Turbo motors tend to run higher egts, so having a lil extra lubrication on the exhuast valves is good juju. But, again if there's too much clearance they'll puff.

On properly done heads, I've seen no difference. Personally, I don't run them unless I have a question about how loose the valve to guide clearance is.

 

[gofstbuick]

When my heads were first set up, the stock guides were too loose and in the morning it puffed. On the second go around, instead of knurling the guides, the machinst installed liners. This brought the clearances to within spec. The SI exhaust valve does not have provisions for a seal and I ask that they be left off. On the first valve job, it puffed after 1000 miles. I just learned to live with it. There is 3000 on this recent rebuild and it's not puffing and I expect it won't as long as I keep the maintenance up (which has never been an issue). The other issue you may need to be concerned with is retainer clearance. How will the installation of a valve seal (that wasn't installed by the factory) affect the clearance between the spring retainer and seal? Researching, I looked at Ferrea, SI and Manley valves. The Ferrea and SI valve stem length were close to each other, but the Manley valve was much longer. I would have had to use the Manley valve to obtain the the proper retainer clearance for the vavle seal. But I also wondered, at what expense to the valve train geometry. How much more would I have to change to get back to the proper geometry. As it sits right now, there is a 3 angle valve job, with 2 angles on the face of the valve. I used a combination of 0.050 plus retainers and keepers to keep installed height within 0.002 and stem heights within 0.002. You could lay a straightedge across the stems and not see any light. There are three 0.015 spring shims spread across both heads. Before each seat was ground, the stones were dressed. Kind of extreme, but I got a great valve job.