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8N Valve Guide seals

J

John Ayres

Member

In the process or rebuilding a 8N engine and bought new valve guides. When we took the old ones out there was a seal on the outside of the valve guide on the intakes but not the exhaust. It isn't really a seal as it does not go around the valve but the outside of the valve guide. The rebuild kit from Yesterday Tractors has 8 of these o-ring/seals. Do we use all 8 for intake and exhaust or just 4 for the intake and have 4 extra? Thanks, John Ayres
 
I used all 8 of them myself, but a lot of people don't put them on the exhaust guides. The way I look at it is that if you only needed 4, there would only be 4 in the kit. They may get a bit cooked from the exhaust temp tho!
 
just use the seals on the intake valve, the heat from the exhaust will melt them if you put them on the exhaust guides. edit, i only got 4 in my kit so...
 
(quoted from post at 07:29:32 09/01/10) just use the seals on the intake valve, the heat from the exhaust will melt them if you put them on the exhaust guides. edit, i only got 4 in my kit so...
Click to expand...


I have not seen that many flathead exhaust guides to have any real first hand knowledge .

I do doubt that it would get hot enough to melt them out though .

Since it is on the pressure side and not the vacuum side they would not be a factor in performance .

The exhaust guides would expand with heat so seals would probably not be necessary and soot would also probably fill any leakage .

I have never heard off exhaust seals being a problem . Maybe an old wife's tale ???

I don't know , but I would install them if I had them . Of course I pay my own bills so I can gamble with my time and money . Your mileage may vary .
 
John:

The large square cut O ring type seals are not valve seals but rather valve guide seals.

They are intended to prevent intake manifold vacuum from drawing engine oil into the combustion chambers around the intake valve guide seals.

Use the seals on the intake valve guides ONLY.

Dean
 
(quoted from post at 10:10:46 09/01/10)
In the process or rebuilding a 8N engine and bought new valve guides. When we took the old ones out there was a seal on the outside of the valve guide on the intakes but not the exhaust. It isn't really a seal as it does not go around the valve but the outside of the valve guide. The rebuild kit from Yesterday Tractors has 8 of these o-ring/seals. Do we use all 8 for intake and exhaust or just 4 for the intake and have 4 extra? Thanks, John Ayres
Click to expand...

As Dean points out their purpose is to prevent vacuum leaks on the intake manifold side - which is a none issue on the exhaust side. I don't think it was an oil control issue as much as a fuel mixture control issue but that's just my opinion. And FWIW the Master Parts Catalog lists the quantity required as 4 and specifically identifies them as being for the intake guide bushings. Not to mention they are a royal PITA to install.

TOH
 
Mine had valve guide seals on intake and exhaust valves. The exhaust ones were not melted, burned up or anything so I put new uns on exhaust and intake..To each his own. All guides have the groove for the seals so what can it hurt??.....Nothing..
 
(quoted from post at 20:13:46 09/01/10) All guides have the groove for the seals so what can it hurt??.....Nothing..
Click to expand...

Ummm - probably nothing more than a couple extra busted knuckles fighting with the additional ones :D

TOH
 
That is my question. Im in the process of doing a valve job on 39 N and there are no seals on any of my valve guides but the new kit comes with 8 of them. How the Heck do you get those suckers in. With the seal on the guide it wont fit in even with a ton of lube and gentle persuasion. Whats the trick?
 

Sometimes I can work them past the ports in the block with a screwdriver and a little pressure them sometimes I can not...

Always use silicon dielectric compound around the seal its one of the best rubber lubes out their...

On the tuff ones I just drive that mutta in and move on with life...

Not all those seals are hard to get in I think its in the seals, if they put up a fight I win with a BFH drive'em home...
 
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