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I'm going to replace the seals and have a question. I plan to remove all the spark plugs and all the rockers. Then use an air compressor to pressurize the cylinder I'm working on. I've watched some videos and some mention putting the cylinder at TDC when pressurizing the cylinder, and some don't, My question is: if you don't have it at TDC, I assume with all the plugs removed, it would spin the engine to where the cylinder is now at the bottom. I'm thinking I could prevent that if I wanted to by putting it in gear when each cylinder is turned to TDC.
But assuming it will still pressurize just fine it it moves the cylinder to the bottom. the only reason to put it to TDC would be if that would prevent the valve from falling all the way in the cylinder if the air pressure was lost. But if you would still lose the valve if you lost pressure at TDC, then what is the point of turning the engine to TDC on each cylinder?
I would suggest using a piece of clothesline in the spark plug hole and rotating the engine until the piston compresses against the clothesline. Do one valve at a time so the rockers all go back on to the exact same valve.
I have quite a number of valve spring compressors but the one that has 2 claws that grab the bottom of the spring and screws down over the top of the valve to compress the spring is the right one to use here. MUCH better.
Cotton clothes line and spring compressor fom NAPA
Last edited by stingr69; Aug 13, 2020 at 07:39 PM.
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Strictly an amateur here. Recently did the job on my NOM BB. I couldn't get the rope in the cylinder easily so I went with compressed air. My pistons were at top dead center and about 60lbs of pressure held the valve up and did not move the piston down. If the piston is not at the top then the air pressure will move it down. It's my understanding that the valve will not drop to the point where is can't be recovered if the piston is at top dead center. Definitely have a magnet to capture the keepers. Since my engine was a NOM and I had no history on it I mic-ed the stems before I bought the seals to ensure I purchased the correct diameter.
The first thing to do before anything else. Shove sheets of paper towels in all the oil return holes in the top of the head.
Because you removed all the rockers for unknown reasons, you can not watch the valvetrain sequence to verify what stroke the cyl is on.
I have the sparkplug hole air hose adaptor but, with headers it was impossible to use on three cyl. On the other 5 cyls I found that 70-80 lbs of pressure struggled to keep the valve closed when the spring compressor was used.
You can tap the valve retainer with a rubber mallet to release the split-locks.
Like sting said, get some soft 1/4" rope and start shoving. It holds the valve much better anyway, does not force the piston down and eliminates that annoying hiss of compressed air trying to escape. The rope keeps the valvestem tip right where you need it when installing the split-locks.
Last edited by HeadsU.P.; Aug 13, 2020 at 06:46 PM.
Just my $.02. If your valve seals are so bad that they need replacing, chances are at least one or two valves may not seal and the procedure may ruin your day. Why not just pull the heads, do it right, and while your at it, decarbonize your piston tops, combustion chambers, valves, and do a manual valve lap. Your motor will thank you for it.
The car has 60m miles and runs fantastic. I get a little puff of smoke on startup and let’s not forget the car is 48 years old and the engine has never been opened. This is the far easier route and to be honest I don’t have the time to be tearing the engine apart. That’s a scenario that can end up with a car never being put back together, if it isn’t your top priority. I’m 65 and retired and right now golf trumps the Corvette.
Well, you're right. Pulling the heads adds a lot more labor, a few more gaskets, several more moola$.
The key to changing the seals, from a nightmare to pleasurable is the "spring compressor". Decades ago, I had a one hand lever style. What a nightmare trying to get the split-locks on & off with the other hand. Now I have the "cam-over" style. Much easier.
Don't cheap-out on the seals. Get some purdy blue ones that stay on the guide like they are suppose to. Skip the cheap "O" Rings that end up in your oil pickup screen.
Last edited by HeadsU.P.; Aug 14, 2020 at 08:52 AM.
Done this job many times......use the Sealed Power "umbrella" type seal.......cheap and works well......
I use air and the bar style spring compressor...and a magnet in the other hand near the keepers to keep them from going places where you do not want them too.
While you are there......buy the Elgin Z/28 spring/lock/retainer kit for $100.......gets rid of the rotators and freshens the 48 year old springs.......a true bargain.
The car has 60m miles and runs fantastic. I get a little puff of smoke on startup and let’s not forget the car is 48 years old and the engine has never been opened. This is the far easier route and to be honest I don’t have the time to be tearing the engine apart. That’s a scenario that can end up with a car never being put back together, if it isn’t your top priority. I’m 65 and retired and right now golf trumps the Corvette.
My $.02 again. if the car runs fantastic, except for a puff of smoke on startup, I wouldn't even bother messing with the seals. Plus it may not even be the seals causing the issue.
[QUOTE=REELAV8R;1602015945]Jeeze, just let the guy change his valve guide seals.
.Sorry, just my thoughts, you can take it or leave it. Good luck with your project. Please let us know how easy the job goes and if it solved the problem.
Replacing Valve Stem Seals
