pletzvet

My '85 with 120,000 miles is due for new valve seals. Anyone do this recently and have any quick tips and suggestions to avoid dropping a valve down a cylinder? I don't want this job to get bigger by taking a head off to find a stray valve. Also, any suggestions for what type of seals to use would be appreciated too.

Demonic85

Chances are if yours has a lot of miles on it (like mine) then you'll need to have the valve guides themselves worked on as well or oil will still leak past the seals.

For me I just said screw the whole thing and bought new heads, but that costs a lot more.

John A. Marker

You want to rotate the engine (by hand) until both valves are closed then use air to hold the valves closed. It is not the TDC that is as important as holding the valves firmly CLOSED. When you compress the spring, the air should hold the valve closed so that is does not drop. Granted, if the piston is at TDC (not BDC) it will not drop far. But now you would have to pull up the valve, hold it and slip the seal on and in place. You want the valve up tight against the head and not part way down when you slip on the valve seals.

The rope trick does the same thing. You insert the rope into the cylinder and then run the piston up which compresses the rope against the valve holding it tightly closed.
Both work well. But again, you want both valves closed tightly. If the piston is at BDC, the valve is not closed and held against the head. I used air because it is fast as compared to stuffing rope and then rotating the engine to compress the rope against the valve and rotating the other direction when finished with that cylinder and pulling the rope out.

In most cases, the guides will be fine. I replaced my seals only at about 130,000. Then changed to AFR heads at about 160,000. The old L98 heads with the new seals went on my 74 Blazer when I changed out the engine two years ago. No oil smoke when I start the Blazer currently!

AGENT 86

Yes, if the valve is not fully closed, you will have a hell of a time compressing the spring far enough to get the locks in.

pletzvet

John, - Did you find that when you put air into the cylinder that it did NOT push the piston down toward the bottom? Do you recall the PSI range that you used? I'd feel a little more comfortable using the air if I knew the piston was near TDC - just in case.

Hotred94

I had no problems when I did mine with air--fast, easy, no problem. You remove the rockers and the valves are all sealed in top position. I had something like 30lbs of pressure. The engine moved only one time, but if you have a manual just leave it in gear. This method is much faster and somewhat safer than the rope method (no rope residue or chunks of debris in the cylinder).

Chatman

I would like to ask a question about the compressed air method for my understanding.

If you begin working on a cylinder by loosening the rocker nuts, then why would you care whether the cylinder was at the top of the stroke? The valves are closed except when forced open by the rocker, right? You loosen the nut, the valve will be closed. Done that way, it doesn't seem to matter whether the compressed air forces the cylinder to the bottom or not. Let it move if it wants to.

The only reason that I can see to be at the top of the stroke is as a backup in case the valve were to fall. In any event, it doesn't matter whether it is on the compression stroke.

What am I missing?

genefree3

You are correct, once you back off the rockers the springs do close the valves. Myself, I just crank up the air to around 100 lbs and have at it. My personal preference si for the piston to be at the bottom of the stroke. Then there is no possibility of the valves dropping. I have done this numerous times and never had a problem. The first one cylinder sill probably take you fifteen minutes, by the time you do one side you'll have it down to 5 mins per cylinder. It will take less time to do it with air than the time it would take to get rope into cylinders.
If you have any questions, pm me and give me a phone number and I will call you back.
Gene

pletzvet

Very helpful discussion...I just have to get past the worries about dropping a valve down the cylinder, hence the TDC questions. So, if I understand correctly - as a minimum, 30 psi, will keep the valves seated, and 100 psi has the potential to push the piston downward. Actually 30 psi, is lower than I'd expected. Based on your experience(s), what kind of air flow rate (i.e. minimal, moderate or high) is required, assuming that there will be leakage past the rings and I assume some at the valve seats too?

Since I started the thread, I'll diverge a little - there seems to be lots of choice on manufacturers and type of valve seals - what is recommended, keeping in mind that the engine is stock and not being raced.

Thanks

pletzvet

Yeah, you're right - the only concern about the piston staying near TDC regardless of compression or exhaust stroke is the safety backup in the event of sudden, unexpected loss of air flow. If the piston isn't at the top the valve drops - I'm taking a head off.

pletzvet

Gene, did you find an adaptor with a quick connect that could be threaded into the spark plug hole and quick connected to your air hose? If so, where'd you find one?

genefree3

Peresonally, if I am going to spend the time doing it I am going to install teflon seals. As far as the volume of air, your're only filling one cylinder with air at a time. Roughly 44 cubic in. of air, even a poor compressor will kick out enough volume to accomplish this. Worry more about the breaker getting tripped when your wife plugs in her curling iron

John A. Marker

I used about 100 PSI when changing the seals. This was not a problem since you are doing only one cylinder at a time. If you have one valve partially open you can here the air rushing into the exhaust or out the intake. By having the cylinder you are working on at TDC it is a safety backup just in case SH*T happens! This worked fine on my 85 and on the 86 of a former Forum member that I helped install seals on his Corvette.

I used FELPRO valve seals all the way around including the exhaust valves. The seals come with a (1 per box) plastic sleeve that fits over the top of the valve and keeps the seal from being cut by the keeper (retainer) groove cut into the top of the valve stem when you install the seal. I dropped my seals into a small jar of oil before installation so they would slip on easy.

I did one cylinder at a time starting with #1, then rotated the crank until another cylinder had both valves closed and moved to that cylinder. You may find that when you depress the spring the valve will drop and the keeper will not release. Take a rubber hammer and tap the top of the valve retainer then try again. If you don't have the cylinder at TDC and you start to compress the spring and the retainers pop off the valve WILL drop, take the extra time and bring the piston to TDC. Use a small magnet and very small needle nose pliers to grab the retainers. I would suggest placing a couple of shop rags around the valves you are working on just in case you loose a retainer. Better they fall onto the cloth than into the engine or loosing one someware in the engine bay. By the time you turn the crank 360 you will have finished all the valves and will be back on #1. If you have a L98 you can adjust the following valves (line up timing mark and be sure you are on compression on #1)....EXHAUST 1, 3, 4 and 8....INTAKE 1, 2, 5 and 7. Then turn the crank 180 and line up the timing mark again and adjust EXHAUST 2, 5, 6 and 7...INTAKE 3, 4, 6 and 8.

I built my own spark plug adapter by taking an old plug and cutting it off and breaking out the insulator then welding a cut down quick disconnect. This worked fine....even on the toughest #8.

It isn't too difficult to do and a great learning experience

-John

pletzvet

I have read about using basic geometry to figure out where the 90, 180, 270 and 360/0 degree points are on the harmonic balancer. Then mark these on a piece of masking tape and carefully tape it on the circumference of the balancer. Is that how you identifed the 180 mark?

John A. Marker

This might be a little confusing.....the 180 is in reference to the distributor. When you turn the crank a full revolution (360 degrees) it only turns the distributor 180 degrees. So if you turn the crank once and line up the timing marks you have only turned the distributor 180 and then you adjust the other set of valves as I indicated above in the prior thread. Turn the crank another full revolution (360 degrees) again and you are back where you started with both #1 intake and exhaust valves closed. This is a FOUR STROKE ENGINE THING>>>>>

pletzvet

Okay, I see what you were meaning - makes sense to me now.
Thanks

rich653

I used a compression tester hose to screw in the cylinder and then quick connect to air hose, it's on a rubber hose so it worked great, just have to take the schrader valve out of the spark plug end of the hose. If you don't have a comp tester you can get one pretty inexpensive at Harbor freight I paid 14.99 has all the connections and you end up with a comp tester. if your interested the pn is 95187-4vga. If you don't have a store close you can order online www.harborfreight.com. Oh I marked the balancer like you had said in 4 spots started at tdc and with #1 cyl and then followed firing order around stopping at each mark and adjusting 1 valve, 2 spins around and I was done. Put the vc's back on and they haven't been off since. There is a lot of ways to adjust valves and a lot of guys here will tell you with the covers off and engine running but it is messy, so whichever way you feel good about, go for it. Good Luck

pletzvet

This is a little long as my intention is to share with others how my valve seal replacement job went; read only if interested...

Thought I'd just do an update to this thread that I started a while - I just finished changing the valve seals this past weekend. The job went pretty smoothly with only one interesting finding. The o-rings were as hard as rocks and broke into pieces as I was pulling the retainer over top of them in most cases. The exhaust valve umbrella seals were also really hard, but they actually seemed like they might have been hard from the factory, - they were a reddish-brown colour and were loose on the valve stem, but seemed more like a plastic material than any kind of rubber compound. But maybe they just got that way over the years. The intake umbrella style seals were the postive style valve seals, and still had some pliability but were loose on the valve stem. I replaced all seals with Victor-Renz teflon seals.

I played it safe and followed the firing order bringing each pistion to just a few degrees before TDC on the firing stroke ( I stuck a wire probe into the spark plug hole on my first cylinder to make sure that the piston was sitting there). I locked the crankshaft (the car is automatic) using a pair of vice grips with a rubber hose slipped over the jaws and gripping it to the crankshaft pulley and the vice grips were up against the rack. If the air pressure was going to turn the engine over, it would have to turn it backwards and the vice grips would jam things up. I used about 75 psi of air to hold the valve closed when I tapped the retainer off the keepers and then I used about 30 psi to hold the valve in its seat when installing the new seals. In between, I shut the air off and the valve would drop about an inch and rest on top of the piston. Dabbing some oil on the valve stem and dipping the seal in some oil just before installing made them slip on easily. I tapped the positive valve seal on each intake valve using a long socket (13mm I think) and made sure that the tower and seal were well oiled. I gave up on the little condom-shaped sleeve after the frist cylinder because it was a pain to remove, and the grooves on the valve stem are tappered as the seals slide down the stem anyway, so there was no danger of tearing the seal. With the spring compressed it was easy to slip the o-ring onto the second groove, making sure that it turned in the groove and didn't have any rolls. Note: make sure that the compressed spring and retainer are down on the tower before slipping on the 0-ring seal as the spring presses the retainer up against the bottom of the o-ring while the keeper sits above the o-ring. Once everything was back in place with spring tension, I tapped each keeper to make sure it was fully seated in its groove.

The interesting thing...I discovered a couple of pieces of damper spring on the right side. I inspected each spring, keeper etc when doing each valve and found that the dampers for BOTH the intake and exhaust valves on #4 cylinder had broken. My local NAPA friend found me a couple of used dampers in the back of his shop to replace the broken ones. I trust that the extra pieces of damper managed to find their way to the intake valley or to the oil pan and will mind their business while sitting there!! I'm going to put a magnetic oil drain plug in the oil pan to pick up any stray pieces. The oil pump screen should keep the pieces from gettng back into circulation - I hope! It was interesting that this occurred on #4 cylinder because when I removed the spark plugs, #4 was the only one that was darker than all the others which were a nice whitish/barely tan colour. Anyone see a relationship between the darker plug and the broken dampers on the valves for that cylinder???

Anyway, I'll stop the essay - just thought some might enjoy the read if you are contemplating doing the job yourself sometime. A pretty straightforward job, just a bit time consuming, especially if you are meticullous and inspecting carefully as you proceed. Any questions, or comments - send 'em.

John A. Marker

Glad it went well. It really isn't difficult once you get into it. A little time consuming doing one cylinder at a time, but it beats having to pull the heads, new gaskets for the heads, exhaust manifolds and then torque the heads.

From the information I have found, the inner spring "dampener" doesn't really assist in spring pressure. It is there to reduce vibrations that occure at different rpm. Sure you noticed, but the dampener is wound the opposite direction as the spring itself.

Did you check the old seal on #4? It may have been damaged by the broken dampener and allowed a little more oil to pass by the seal. This would be my best guess. On my old iron heads I epoxied small wire screen over all the oil return holes in the heads. I had added roller rockers and felt that if one fell apart the screen would stop the parts from getting into the rest of the engine. Worked great, never had a RR fail, but it did keep out gasket materials from the valve covers.

JOB WELL DONE Give yourself an Attaboy.

-John

pletzvet

[QUOTE=John A. Marker;1565211351]

Did you check the old seal on #4? It may have been damaged by the broken dampener and allowed a little more oil to pass by the seal. This would be my best guess.

Yes, I checked the seals on #4 and the 'plastic-like' umbrella seal on the exhaust valve was pretty much destroyed, but the intake (positive-style) seal seemed to be in as good shape as any of the others. The other thing about #4 intake that I discovered was the oil shield that fits between the retainer and the spring was pretty badly mangled, both on the bottom edge as well as the centre hole was worn badly out of round. Clearly a piece of the dampener must have been putting some pressure on the top of the spring for a while to do that damage. By the way, both dampener's broke on the top side just under the retainer.

I also found a lot of very fine metal filings laying around the head bold back at #8 cylinder. I'm thinking that these would have come mainly from the oil shield - and it looks like this condition had existed for quite some time. Am I right in thinking that the remaining chunks of dampener are either sitting in my intake valley or on the bottom of the oil pan and in either case should not present a significant risk?