Valve replacement for 9 n

(quoted from post at 19:14:55 07/31/15)
There are no valve seals but there are valve guide seals for the intake valve guides.

And the exhaust valves do not use the valve guide seals; my kit has 8 valve guide seals. Thanks for your previous reply.
 
As bill said, kits come with 8 seals--wonder why?? I guess they they figure every other one will split when trying to install....my 2N had seals on all guides so I put seals back on all guides--ones I took off were not melted or brittle as most say they will
do..Anyway it had 8 on it so I put 8 back-won't hurt a thing-left on the shelf they will
just be lost..
 
I realize there is a difference of opinion about putting seals on exhaust guides, but I will give you my opinion. When most of these tractors were built, rubber was in short supply and the compounds were primitive by today’s standards. Due to the higher heat in the exhaust chambers the seals could become brittle and crumble. They could even melt if there was severe leakage. Because of this, it became standard practice to leave the exhaust seals off, and this practice was handed down over the years.
I feel that because of the improvements in rubber formulation this is no longer a problem. I have torn down a lot of these engines (I’ve done 3 this week alone) and any of them that have been rebuilt in the last 20 years or so, have shown no problems with the exhaust seals deteriorating any more than the intake seals. If you find a bad one, there is probably serious valve leakage.
I have heard some say that leaving the seal out helps valve lubrication by allowing a small amount of oil leak past the guide and oil the seat and stem. I find this very unlikely since you have exhaust pressure pushing down, I don’t see how oil is going to go up. This would also cause carbon buildup in the valve chamber.
By installing the seals I believe you do at least 2 things. First, you help reduce the amount of exhaust gas blow by that can contaminate the oil and cause carbon build up on the lower part of the valve stem. I have noticed more carbon and crud in the exhaust ports of non sealed guides than sealed ones. And secondly, the seal helps to keep the guide centered in the bore which can help prevent wear to the side of the valve guide. And that is my two cents. :)
 
(quoted from post at 08:52:16 08/01/15) I realize there is a difference of opinion about putting seals on exhaust guides, but I will give you my opinion. When most of these tractors were built, rubber was in short supply and the compounds were primitive by today’s standards. Due to the higher heat in the exhaust chambers the seals could become brittle and crumble. They could even melt if there was severe leakage. Because of this, it became standard practice to leave the exhaust seals off, and this practice was handed down over the years.
I feel that because of the improvements in rubber formulation this is no longer a problem. I have torn down a lot of these engines (I’ve done 3 this week alone) and any of them that have been rebuilt in the last 20 years or so, have shown no problems with the exhaust seals deteriorating any more than the intake seals. If you find a bad one, there is probably serious valve leakage.
I have heard some say that leaving the seal out helps valve lubrication by allowing a small amount of oil leak past the guide and oil the seat and stem. I find this very unlikely since you have exhaust pressure pushing down, I don’t see how oil is going to go up. This would also cause carbon buildup in the valve chamber.
By installing the seals I believe you do at least 2 things. First, you help reduce the amount of exhaust gas blow by that can contaminate the oil and cause carbon build up on the lower part of the valve stem. I have noticed more carbon and crud in the exhaust ports of non sealed guides than sealed ones. And secondly, the seal helps to keep the guide centered in the bore which can help prevent wear to the side of the valve guide. And that is my two cents. :)
I have installed all 8. They'll do no good on.the shelf. Good discussion, thanks
 

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