well I am going to replace the valve stem seals .I checked tonight ,3 seals are cracked with pieces missing, 3 other seals were riding high off of their position. I pricked the rest of the seals and they are hard, When I replace the seals and push the umbrella seals down what keeps them from riding up on the stem again later? Should I clean the mating surface between the head and the seal dry and clean (or )put a small amount of oil on the seal and then press the seal down? I lubed up the rocker barr and checked all of the rockers. The head looks very clean. I dont think the last rebuild had the valve seals changed. I kinda feel like I am waring this subject out. I am not a big fan of doing things twice.
valve stem seal installtion question
- Thread starter franko66
- Start date
Old Ford Blue
New member
I've certainly been watching all your posts on this subject closely. I need to do them on my 200, with close to 435k miles having never been apart, its due for a set of stem seals.
Good luck, and sorry I can't help ya out.
Good luck, and sorry I can't help ya out.
Nothing keeps the seals down. Just make sure the stems are clean and a little oil won't hurt. They won't ride up enough to come off the base.
I did mine a couple of years ago. All was good afterwards. When I pulled the head last month the seals were still good and although a couple had come up a bit they still keep the oil in control.
I did mine a couple of years ago. All was good afterwards. When I pulled the head last month the seals were still good and although a couple had come up a bit they still keep the oil in control.
LameHoof65
Famous Member
I had teflon seals put on mine about 2 years ago.....haven't had a problem one with them......Of course I haven't started the engine yet either....Ha!
No, seriously...the regular seals are fine....If I was doing it over I wouldn't have paid to have the teflons put on...requires some mild machining and they are easy to break during the install. My machinist broke at least one during the process.
Later, Darwin
No, seriously...the regular seals are fine....If I was doing it over I wouldn't have paid to have the teflons put on...requires some mild machining and they are easy to break during the install. My machinist broke at least one during the process.
Later, Darwin
Howdy Back Frank:
Q- "When I replace the seals and push the umbrella seals down what keeps them from riding up on the stem again later?"
A- The top of the valve stem boss is as cast, so it is somewhat irregular. The seals fit tightly over and with a good bit of grip from the rough surface. The valve stems pass through the guides in a hole that has a flat contact surface on the inside. That smooth, flat surface against the smooth, shinny surface of the valve stem allows the valve to pass through while the seals grip on the guide boss holds tight. Time, heat cycles and wear slowly degrade the seals.
Q- "Should I clean the mating surface between the head and the seal dry and clean (or )put a small amount of oil on the seal and then press the seal down?"
A- Yes, Clean the "Bee hive shaped" top of the stem boss and add a drop of oil to the inside of the ring seal that the valve stem passes through. When pressing the seal down take note that it is not cocked off center. take a minute to make sure each seal is completely seated and centered on each boss.
FYI- on startup, watch the oil as it seeps from each rocker, from back to front. It should take no more then a minute until all rockers are receiving oil. The flow of oil over the rockers, springs, valve stems and seals is what keeps the top end lubricated and cooled. THe oil comes up from the rear staunchion, passes through the rocker shaft to each rocker and then out to the valve assembly. There is a good sticky at the top of this forum on the oiling system on the top end and how to clean it up and improve on it.
Keep us posted on your progress.
Adios, David
Q- "When I replace the seals and push the umbrella seals down what keeps them from riding up on the stem again later?"
A- The top of the valve stem boss is as cast, so it is somewhat irregular. The seals fit tightly over and with a good bit of grip from the rough surface. The valve stems pass through the guides in a hole that has a flat contact surface on the inside. That smooth, flat surface against the smooth, shinny surface of the valve stem allows the valve to pass through while the seals grip on the guide boss holds tight. Time, heat cycles and wear slowly degrade the seals.
Q- "Should I clean the mating surface between the head and the seal dry and clean (or )put a small amount of oil on the seal and then press the seal down?"
A- Yes, Clean the "Bee hive shaped" top of the stem boss and add a drop of oil to the inside of the ring seal that the valve stem passes through. When pressing the seal down take note that it is not cocked off center. take a minute to make sure each seal is completely seated and centered on each boss.
FYI- on startup, watch the oil as it seeps from each rocker, from back to front. It should take no more then a minute until all rockers are receiving oil. The flow of oil over the rockers, springs, valve stems and seals is what keeps the top end lubricated and cooled. THe oil comes up from the rear staunchion, passes through the rocker shaft to each rocker and then out to the valve assembly. There is a good sticky at the top of this forum on the oiling system on the top end and how to clean it up and improve on it.
Keep us posted on your progress.
Adios, David
Answer: I was under the understanding that the bottom of the retainer pushes the umbrella down when the valve is at full lift and that anything over a slow idle, especially after broken in, the valve moves too fast for the weight of the umbrella to move so it stays down until the engine is shut off then it may cling to the stem and ride up. Something about a body at rest tends to stay at rest.
I thought the job was to just deflect oil hence "umbrella seal"
Howdy All:
Dragstang wrote- "I was under the understanding that the bottom of the retainer pushes the umbrella down". The bottom of the retainer should not ever hit the valve seals. It it did it would destroy the seals very quickly. This can become a problem when using a high lift cam and/or high ratio rocker arm. It is not good! One of many things to check for when using very high lifts an close tolerances is retainer clearances to the valve guide boss.
No, the seals just set on the top of the bosses with the valve passing through. I thought the analogy of XFlow's of an umbrella was a good one. Thanks.
Adios, David
Dragstang wrote- "I was under the understanding that the bottom of the retainer pushes the umbrella down". The bottom of the retainer should not ever hit the valve seals. It it did it would destroy the seals very quickly. This can become a problem when using a high lift cam and/or high ratio rocker arm. It is not good! One of many things to check for when using very high lifts an close tolerances is retainer clearances to the valve guide boss.
No, the seals just set on the top of the bosses with the valve passing through. I thought the analogy of XFlow's of an umbrella was a good one. Thanks.
Adios, David
I can assure you that the retainer does contact the seal at low speed. It may not show up in the picture, but there is wear marks on the bottom of the retainer. As you can see in the picture, one valve seal is up and one is down and you can see where the stem is polished all the way up to the bottom of the retainer. How else would it get like this if what I say is not true? If you don't have worn out valve seals you can take your valve cover off and see for yourself. Crank it over without ignition, then fire it up. You will see a monkey motion going on with the valve seals till speeds get great enough that they stay down. By the way, there is a 1/16" side clearance on either side between the valve guide and the seal.
Howdy Back All:
Drag-200stang- That is an interesting photo. Your point is well illustrated. As designed the stock type OEM valve stem seals are not supposed to move up and down, even at slow engine speeds, with the valve. My guess is that your seals are mostly worn out, or mismatch to this engine. In normal applications the seals grip the valve stem bosses tightly enough to stay in place. As they age with heat cycles, they tend to become brittle, and lose their elasticity and grip. That could be what happened to yours. Can you see any difference between the intake and exhaust valve seals? Typically the exhaust valve stem seals are the 1st to go. Most often the seals crack where they are stretched around the guide bosses.
Once the seals are off the guide bosses they will likely hover on the valve stem somewhere between the bottom of the retainer and the top of the bosses. They will not reseat themselves onto the bosses. The shine on the valve stem should indicate that the seal is still prohibiting oil from being sucked down the valve guide, much like an umbrella. Are you seeing any oil clouds on hot restart or after high vacuum running?
Thanks for sharing your situation. Mechanics, as designed and in fact, are ocassionally the same. Your photo is proof positive.
Adios, David
Drag-200stang- That is an interesting photo. Your point is well illustrated. As designed the stock type OEM valve stem seals are not supposed to move up and down, even at slow engine speeds, with the valve. My guess is that your seals are mostly worn out, or mismatch to this engine. In normal applications the seals grip the valve stem bosses tightly enough to stay in place. As they age with heat cycles, they tend to become brittle, and lose their elasticity and grip. That could be what happened to yours. Can you see any difference between the intake and exhaust valve seals? Typically the exhaust valve stem seals are the 1st to go. Most often the seals crack where they are stretched around the guide bosses.
Once the seals are off the guide bosses they will likely hover on the valve stem somewhere between the bottom of the retainer and the top of the bosses. They will not reseat themselves onto the bosses. The shine on the valve stem should indicate that the seal is still prohibiting oil from being sucked down the valve guide, much like an umbrella. Are you seeing any oil clouds on hot restart or after high vacuum running?
Thanks for sharing your situation. Mechanics, as designed and in fact, are ocassionally the same. Your photo is proof positive.
Adios, David
