Good evening - I’ve stripped the head of my 1935 14hp and spotted something I didn’t expect - valve stem seals. I’ve had mixed opinions when discussing this with my colleagues. Some say they deprive the valve stem of lubrication.
This argument might be worthy of note. One of my exhaust valves is very stiff in its guide (the springs would not be able to close it).
I’ll try and attach a photo.
I’m hoping for some sage advice
Chris
Valve stem seals - a good thing or not
Re: Valve stem seals - a good thing or not
Hi Chris,
It does sound rather unusual to find valve stem seals. You don't say or perhaps I have missed a post but was the engine running before the strip down? Have you found the cause of the stiff valve problem yet? If all the valves were fitted with stem seals then it is perhaps unlikely that is the cause of the problem. I would have thought that carbon accumulation or lack of use were more likely causes.
I think it is quite a strange thing to do unless these stem seals were an attempt to overcome a badly smoking engine.
While the head is apart, will you be fitting hardened valve seats? Personally, my 14 doesn't have hardened valve seats as yet and seems to run perfectly well with no noticeable valve recession. However, if you do, then it might be worth fitting a new set of guides if there is any doubt as to their condition or else bushing the originals with bronze. If the valve stems and guides are in good order then I see little need for a seal especially on the exhaust valves.
Once you have given everything a good clean and measured the clearances, you will be better placed to determine the cause of the problem and perhaps the reason for fitting the stem seals and how to proceed from there. The engineering in these old Rovers is pretty good and I have often thought if Rovers thought that something was necessary, then then they would have done it. I know times change and there are new materials and lubricants but good practice doesn't change much.
Richard
It does sound rather unusual to find valve stem seals. You don't say or perhaps I have missed a post but was the engine running before the strip down? Have you found the cause of the stiff valve problem yet? If all the valves were fitted with stem seals then it is perhaps unlikely that is the cause of the problem. I would have thought that carbon accumulation or lack of use were more likely causes.
I think it is quite a strange thing to do unless these stem seals were an attempt to overcome a badly smoking engine.
While the head is apart, will you be fitting hardened valve seats? Personally, my 14 doesn't have hardened valve seats as yet and seems to run perfectly well with no noticeable valve recession. However, if you do, then it might be worth fitting a new set of guides if there is any doubt as to their condition or else bushing the originals with bronze. If the valve stems and guides are in good order then I see little need for a seal especially on the exhaust valves.
Once you have given everything a good clean and measured the clearances, you will be better placed to determine the cause of the problem and perhaps the reason for fitting the stem seals and how to proceed from there. The engineering in these old Rovers is pretty good and I have often thought if Rovers thought that something was necessary, then then they would have done it. I know times change and there are new materials and lubricants but good practice doesn't change much.
Richard
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ChrisHallard
- Posts: 13
- Joined: Tue Jun 13, 2023 4:31 pm
Re: Valve stem seals - a good thing or not
Good evening Richard - thank you for your thoughtful, and thought provoking reply.
I’ll try to respond to the points you make in turn.
The engine was running, and had been “sewing machine” quiet. It then developed a worrying knock.
I investigated with my stethoscope and could hear/feel the knock from the rocker shaft pillar between cylinder 2 and cylinder 3 exhaust valves.
In preparation for removing the head I took off the rocker shaft assembly pushrods and tappet cover. I spotted that the cap of the cylinder 3 exhaust cam follower was at a jaunty angle. It was loose! At that stage I thought I had found the culprit.
Nevertheless the head came off.
Then I found cylinder 3 exhaust valve slightly ajar and it needed a light drift to remove it. Two significant issues with the cylinder 3 exhaust mechanism!
The head is clean now and I can see it has inserts on both inlet and exhaust. I don’t know when and why.
9/32” reamer sorted the stiff valve.
Valve reface, some new valves and guides, all seats recut etc. are in process.
But the seals/no seals on rebuild question remains unanswered.
One final bit of information.
Cylinder 1 exhaust valve has a split/crack on the rim and it’s guide is the only one that really need replacing.
Once again thank you for your interest
Chris
I’ll try to respond to the points you make in turn.
The engine was running, and had been “sewing machine” quiet. It then developed a worrying knock.
I investigated with my stethoscope and could hear/feel the knock from the rocker shaft pillar between cylinder 2 and cylinder 3 exhaust valves.
In preparation for removing the head I took off the rocker shaft assembly pushrods and tappet cover. I spotted that the cap of the cylinder 3 exhaust cam follower was at a jaunty angle. It was loose! At that stage I thought I had found the culprit.
Nevertheless the head came off.
Then I found cylinder 3 exhaust valve slightly ajar and it needed a light drift to remove it. Two significant issues with the cylinder 3 exhaust mechanism!
The head is clean now and I can see it has inserts on both inlet and exhaust. I don’t know when and why.
9/32” reamer sorted the stiff valve.
Valve reface, some new valves and guides, all seats recut etc. are in process.
But the seals/no seals on rebuild question remains unanswered.
One final bit of information.
Cylinder 1 exhaust valve has a split/crack on the rim and it’s guide is the only one that really need replacing.
Once again thank you for your interest
Chris