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post #1 of 7 (permalink) Old 09-17-2019, 01:58 PM Thread Starter
 
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Valve seals moved?

Some of my 68 400 valve seals have moved up off the valve base causing the engine to smoke. these 6X heads have the double springs. These seals have a spring wire at the top and a flat type spring "clamp" at the bottom. Can I try moving them back down? What keeps them there? Is this a common problem? I believe the engine doesn't have a lot of miles.
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post #2 of 7 (permalink) Old 09-19-2019, 10:37 AM Thread Starter
 
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Pics of Seals. No responses, everyone on vacation? Pontiac Jim help!
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post #3 of 7 (permalink) Old 09-19-2019, 11:09 PM
 
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Pics of Seals. No responses, everyone on vacation? Pontiac Jim help!
Not on vacation, but just got in from a looooong day at work.

Those appear to be viton valve guide seals. You won't be using the standard o-ring seals - if your valves only have the 1 ring-groove for the split lock retainers.

I personally have not installed those type seals - I let my machine shop do it when they assemble my heads. There is a tool suggested to knock them on to the machined valve guides, but there are a number of forums that address this - some oil up the guides and press them on, others use a plastic protector and slide them on, some use a socket. You just don't want to cut/nick them.

I already posted this on another post. From my research, if the valve guides have not been fitted with bronze guides, the valve stems will need a little oil (just as factory) to keep them lubricated or they can seize. So there are clearances needed between the valve stem and cast iron valve guide. Bronze guides don't need such clearances as bronze is self lubricating and thus tighter valve stem-to-valve guide clearances are used. I assume who ever built the engine knew what they were doing, so I would match up a new set of seals with your old ones.

They almost look like this: https://www.summitracing.com/parts/tfs-51400454

You will need to know what the outside diameter is of the machined valve guide so they fit correctly, and the valve stem diameter. Take a look at Summit as they have a bunch of them and match yours up and go from there.
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post #4 of 7 (permalink) Old 09-20-2019, 02:50 AM Thread Starter
 
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Not on vacation, but just got in from a looooong day at work.

Those appear to be viton valve guide seals. You won't be using the standard o-ring seals - if your valves only have the 1 ring-groove for the split lock retainers.

I personally have not installed those type seals - I let my machine shop do it when they assemble my heads. There is a tool suggested to knock them on to the machined valve guides, but there are a number of forums that address this - some oil up the guides and press them on, others use a plastic protector and slide them on, some use a socket. You just don't want to cut/nick them.

I already posted this on another post. From my research, if the valve guides have not been fitted with bronze guides, the valve stems will need a little oil (just as factory) to keep them lubricated or they can seize. So there are clearances needed between the valve stem and cast iron valve guide. Bronze guides don't need such clearances as bronze is self lubricating and thus tighter valve stem-to-valve guide clearances are used. I assume who ever built the engine knew what they were doing, so I would match up a new set of seals with your old ones.

They almost look like this: https://www.summitracing.com/parts/tfs-51400454

You will need to know what the outside diameter is of the machined valve guide so they fit correctly, and the valve stem diameter. Take a look at Summit as they have a bunch of them and match yours up and go from there.
Thanks Jim! You always come through! I've only pulled one exhaust spring and it has 2 grooves, but no O ring. I found out quickly that the cheap Oreilly spring compressor will not work on these dual springs. I then went with a deep socket with a couple of magnets inside and bopped it with a hammer (with compressed air in the cylinder). It worked! I've seen the picture of the modified flat pry bar and may go that route to install them.
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post #5 of 7 (permalink) Old 09-23-2019, 05:43 PM
 
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Here is a drawing of the parts used on the valve and the assembly. Note the 2 grooves on the valve stem - the lower groove is for the small O-ring seal. The top groove is for the split locks.

Compress the spring retainer below the 2nd groove, install the O-ring seal, then the split locks, and back off on the spring compressor.

Check the split locks to ensure you see a little space between them - you want that. They should not butt solid together or something is wrong.

On aftermarket valves, you typically will not see the second groove for the O-ring seal, so you don't use them. However, you want some type of seal and with aftermarket single groove valves, you want to use the valve guide seals which means you will have to have the guides machined for them to be used.

The other option is to have the second groove machined into the stem by the manufacturer. I do believe companies like Ferrea who manufactures their valves could do this if you did not want to cut down a set of heads for the valve guide seals.

Another thing to note is the oil shield which goes over the spring and under the spring retainer. This is designed to help keep excess oil off the valve stem and thus extra oil going down the valve stem and making your engine smoke out the tail pipe on start up (which can also be a sign of worn out O-ring seals).

Some will leave these off. Probably not a good idea as the shield fits over the spring and the retainer than fits into the shield. My guess is this keeps the spring centered and from walking around. I have never checked, but just putting the retainer on top of the spring may not center the spring as with the shield being used.

Now with the heads I had rebuilt, I used the valve guide style Viton seals and had the guides cut down and installed the bronze valve guides. My machinist ordered new springs as well as the matching spring retainers. With this set-up, no oil shield is needed or used.

The oil shield might also need to be removed for clearance purposes if you have a high lift cam, but I do not know at what lift (if any) that that would occur - so always check you clearances.

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post #6 of 7 (permalink) Old 09-23-2019, 08:05 PM Thread Starter
 
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Thanks again Jim,

I'm still worried that the PS seals are going to ride up on the valve stem but am going with it. The new ones go on nice and tight. Seems that someone would have figured out how to keep them down in place like a groove machined into the guide base and a male groove on the PS seal?
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post #7 of 7 (permalink) Old 09-23-2019, 08:22 PM
 
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Thanks again Jim,

I'm still worried that the PS seals are going to ride up on the valve stem but am going with it. The new ones go on nice and tight. Seems that someone would have figured out how to keep them down in place like a groove machined into the guide base and a male groove on the PS seal?
Nope, just the clamp pressure of the ring on the seal. Suppose you could use some JB Weld on 'em as JB is used on almost anything to bond things together.

It may have simply been that the engine sat long enough for the oil to dry on the valve stem/seals and soon the seal was pulled off due to lack of the oil. That's my guess. Just check them in a few months to see if they are holding.
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