Iam planning to replace my valve stem seals on my 305 tpi iam sure alot of you guys have some experiance in this since i hear that this a comon problem, Ive never done this before, (seems simple enough) just want to know if theres anything I should watch out for. besides that i got a few questions

1. everybody says i need an air compressor to lift the valves, but my haynes book says nothing about needing an air compressor, do i really need one and if soo ..........2

2. whats the name of the aircompressor fitting i need , and where can i get one.

3. what type of air compressor do i need, i hear that i dont need a big one and that a simple air compressor used to inflate tires and things like that will do fine.

 

ok u need what they call a compression tester.. they have an adapter to hook up to the compressor but u cant use one that u plug into a cig lighter... it will need to atleast be able to build 60-80 psi to hold the valve... and your haynes book tells u to remove the heads to replace them... u will also need a valve spring took... pocket magnet, and a steady hand... and take your time.. try to not lost the keepers... the little locks that are there for the retainer... and a word of advise when u get done putting it back to gether tap the top of the valve with a hammer just to make sure the keepers are seated... some can pop off if not done right.......

 

in addition to what 86IROCTHD said, use more light than you think you need, use paper towels or something to stuff into every open hole in the head, & a good pair of needle nose pliers will probably come in handy. also have a bottle of oil to lube the valve stems just before you put the new seals on.
do NOT have the keepers off both valves at the same time, do 1 valve seal from start to finnish at a time, only after you have gotten the first valve spring & it's keepers back together, then move to the next 1.

when you tap on the valve stem with the small hammer to seat the keepers, leave the compressor on, do NOT turn the compressor off until after you have the gotten the valve you are working on fully assembled & the keepers seated

 

I have had no problems running as little as 30-40 psi to hold up valves. Unless your valves and seats are shot, it doesn't take much to seal them. But yeah a tire inflator isn't going to have the quick connect air fitting you need. A compression tester is not required -- typically "compression tester" refers to a pressure gauge used to check cranking compression.

 

Compression testers have one way shrader valves in them. That will have to be removed to use the hose.

Compression testers use industrial ends, not automotive type. So make sure you have the right quick-connect coupler for your compressor.

If its a manual car, make sure its in neutral. When you connect the hose, the piston will go down (this is a good thing).

Use a socket and tap the top of the retainer a few times before compressing the spring. Otherise you'll just keep pusing the valve down with the tool.

Use viton seals. Lubricate with vaseline or clean grease.

Use a big enough compressor.

-- Joe

 

Never mind, thought about it and got it.

 

ok soo iama
1. remove the rocker arm
2. compress the springs
3. remove the keeper using a magnet
4. remove the springs ( valve should drop i guess?)
5. turn on the compressor to lift the valve
6. remove and replace the seals using lube
7. put the springs over the valves (still compressed)
8. replace the keepers taping it into place
9. decompress the springs
10. celebrate with a sandwich

hows that sound?

 

That's a good way to drop a valve into a cylinder...then you HAVE to pull the head. Here's the procedure if you have an air compressor:

1 Pull the valve covers, and the spark plugs.
2 Remove the rockers and puchrods.
3 Put your compression gauge hose, with the schrader valve removed, in the #1 plug hole, and hook up/turn on the air compressor.
4 Tap the spring retainer of the #1 exhaust valve with a hammer to unseat the keepers.
5 Compress the #1 exhaust spring, and remove the keepers with a magnet.
6 Remove the compressed spring and leave it compressed.
7 Remove the old seal, lube and install the new seal.
8 Reinstall the spring and keepers, then decompress the spring.
9 Tap the top of the valve with a hammer to be sure the keepers are seated.
10 Repeat 4-9 for the intake valve.
11 Disconnect the compressor and remove the compression gauge hose.
12 Repeat 3-11 for the rest of the cylinders, one at a time.
13 Celebrate with a sandwich, and a beer.


There's a way to do it without a compressor, but it takes a little more time. Instead of filling the cylinder with air, you stuff a length of 1/4" thick string or cord into the plug hole (leaving one end hanging out so you can remove it!!!!) and then turn the crankshaft to bring the piston up until it stops. The piston will hold the string against the valves, which will hold the valves shut. Make sure you remove the rockers before you put the string in, otherwise it could hang in the valve seat and hold the valve OPEN.

 

YOU DON'T WANT THE VALVE TO DROP!

1. remove rocker arm and pushrod
2. remove spark plug corresonding the rocker/push rod you just removed
3. turn on compressor, screw in compression tester fitting (after removing the schreader valve in the end) and connect the opposite end of the compression tester fitting to the compressor after it has built pressure.
4. take a socket and tap the valve spring retainer to make sure it slides freely on the valve
5. compress the spring
6. remove retainer, then the round spacer, then the spring
7. pop the old valve stem off the stud with a straight blade screw driver
8. lube the new valve stem and drive it on with a deep socket until it bottoms out flush
9. place spring on the valve with round spacer on top
10. compress the spring and install retainers
11. tap the top of the reassembled valve lightly with a hammer to make sure the retainers are holding
12. repeat the steps on the other valve for the current cylinder
13. disconnect the hose from the compressor to the compression tester fitting (air will exit the cylinder through this tube) and reinstall plug
14. repeat process for the following cylinders

 

i would like to add that the little plastic sleve that comes with the seals is a good thing oil it and use it good luck

 

You could always use rope if you don't have a compressor...

 

I've heard of the rope method too, and it seems like it would work as well. Knowing my luck, I'd probably tap the valve just right while the air was holding it and end up dropping it in the cylinder. If you do decide to use the air method, Jeg's mail order has the air fittings you need in their engine tools section. It's only about 14 bucks for them. Probably be easier than "rewiring" a compression tester to do the job. And I'd at least use a craftsman type compressor or campbell-hausfeld or something along those lines. I wouldn't trust one of them cheesy electric ones you use to pump up bicycle tires and air mattresses with. Good luck!

 

Thanks guys, I used a lot of your tips.

Advanced Auto Parts and Sears carries a compression tester that has a 1/4 quick disconnect on the other end. You just need to take out the shrader valve so air will travel the other direction. I used this when I did my seals over the weekend since no one carries anything else. I also used the car starter to find the compression stroke of the cylinder that I was working on. As soon as your on the compression stroke your air hold adapter will shoot air out and let ya know. Then plug your line back into your compressor. I did one cylinder at a time and left all the other spark plugs in. Of course I broke two of my spark plug wires taking them off. They seem to always glue themselves on my car.

 

How much was the kit, I need to do it aswell.

 

This job is so much easier with the heads off, plus you can inspect
your valves at the same time.....good luck to ya man!

 

Some people will say not to do this, but my buddy works at a hot rod shop and says they have never had any problems and they do this on EVERY SBC. Use Felpro viton intake valve seals on both the intake and exhaust valves. Those umbrella seals just plane suck. I used the the compessor method but i had the engine out of the car so it was pretty easy. It would have been a much bigger pain doing it in the car. another thing that helped me was to use a little dab of grease on the keepers when re-installing them to hold them in place untill decompressing the spring.

 

Thanx guys, ill let u know how it turns out

 

I too use the positive-type Viton seals on all 16 valves.

Doing them in the car is not so bad. I did my '91Z (which has 218k miles on it) a couple of weekends ago. It took about 3 hours.

You don't have to find the compression stroke to do this. When you take the rockers off both valves will close, which effectively makes EVERY stroke the compression stroke.

I don't like the Jeg's tool because you have to hook the air hose up right there at the head, under the exhaust manifold. A compression tester hose puts the disconnect about 10-12" away from the head, which makes it MUCH easier to get the air hose on and off.

 

Man, I'm really enjoying this post! All sorts of good tips on doing this particular job. The dab of grease for the keepers is an excellent idea. Great J had a couple of good points too. You're right man, every stroke is the compression stroke with the rockers loosened all the way. The type of seals you suggested was good info too. And as far as that tool from Jeg's goes, I don't own it either, I just suggested it as an option. I like the idea of the compression tester better, it does sound like it works better. Besides, if you buy the compression tester, it has more than one use to boot!

 

I have used nylon rope to do this on my 4WD truck. You don't have to worry about dropping the valve. It does help to have a spring compression lever. It makes life ALOT better.

 

This a dang fine time to replace the (probably) fatigued valve springs....

 

I did it that way so that I could adjust the rockers when I was done with that cylinder.

 

Makes sense. I prefer to hot-lash my rockers....it's a bit messier but I find it provides more consistent results.

 

I agree. I usually do a little of both. I'll cold set them just to get them in the ballpark, but adjusting them while it's running seems to be the best method of getting them dead on.