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Discussion Starter #1
I'm gettin oily plugs so I need to replace the valve stem seals on my 302. If I pull the heads, it's easy, if I don't then I have to contend with the clearance between the headers and the plug holes since I'd use compressed air to hold the valves open. I have to use a shorty plug on #5 since I can't get the plug wire boot over a standard plug for this cylinder so I'll never get a stiff pressure hose in there. Do you need to pull the headers or is there some type of angle adapter that can be screwed into the plug hole to direct the air hose to the side to clear the header tube and if so where do I find one?

How much air pressure have you guys used to hold the valves in place and does any particular manufacturer make a hose and connector that is better than another? I guess I could pull the heads or is that way more trouble than what it's worth?

Any recommendations on seals? Thanks for your help.
 

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Never done it, but I have that you can feed rope in through the plug hole and do the same thing.
 
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Never done it, but I have that you can feed rope in through the plug hole and do the same thing.
I've used the rope method and it works fine, an added advantage of the rope method is you don't have to worry about your compressor taking a vacation in the middle of the job and dropping a valve into the cylinder.
 

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Discussion Starter #4
I hadn't thought about using rope, but you make a good point about the compressor plus if I want to take a break I don't have to leave the compressor running and this would solve the header issue with cylinder #5. So, you just feed in the rope until no more will feed and then manually crank the engine to TDC for that cylinder, right? Will this method hold the valves tight againt the piston so there is enough resistance to get the job done?
 

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Chris, I have never used the rope but have seen and heard of guys using it. I see where you are having an issue with the hose. I have always used the hose kit out of a compression tester, just changed the air coupler tip. The hose is about 12" long and quite flexable.

You could loosen the entire header from the head and lay it back to use the hose. it will also give you room to work with the rope.

When I did get to using the air to change the valve spring or seal, I found that the valve stem was loose in the guide, telling me that I needed new guides or having the old guide knurled and that required removing the head.
 

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Small bungee cord works good.
 

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Discussion Starter #7
Don, just out of curiosity, when you found the stem loose in the guides, how loose is loose? I assume that the tolerances are pretty close so is it noticeably loose so it can be wiggled back and forth or are we talking thousandths? I'm also curious as to what type of seals. The umbrella type make sense to me, the o-ring around the top of the valve stem don't. I can see how the umbrella type would shed the oil, but an o-ring at the top, how's that help?
 

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So, you just feed in the rope until no more will feed and then manually crank the engine to TDC for that cylinder, right? Will this method hold the valves tight againt the piston so there is enough resistance to get the job done?
Remove all your spark plugs, locate the piston at BDC for the cylinder you are about to replace the seals on, feed as much rope into the spark plug hole as you can then rotate the crank with a breaker bar by hand so it pushes the piston up into the rope and compresses it against the valves. Never had one that didn't hold the valves tight into the head to get the job done.
 

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Don, just out of curiosity, when you found the stem loose in the guides, how loose is loose? I assume that the tolerances are pretty close so is it noticeably loose so it can be wiggled back and forth or are we talking thousandths? I'm also curious as to what type of seals. The umbrella type make sense to me, the o-ring around the top of the valve stem don't. I can see how the umbrella type would shed the oil, but an o-ring at the top, how's that help?
Can't really measure thousands as if the cly is aired up, its hard to do and the valve head is pushed up into the head seat. With the bunge cord method, you can wiggle the top of the stem , providing you don't have the cly up so tight on the valve. Backing off a little might let you do this but don't go too far as you don't want the valve to drop into the cly, then you have to pull the head.

If you are using the round nose umbrella seal, the ford type, that works providing the under body of the seal is seated on the valve guide stem. Even putting the o-ring on the valve just adds to sealing, as thats what the factory always did. But over time , guys put the ford type seal on as they didnt want to mess with replacing guides.
 
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