Valve stem seal replacement questions

[Spetz]

Hey guys,

I am about to embark on a valve seal replacement.

I will be feeding rope down the spark plug hole to make sure the valves don't drop.

I plan to feed it through some PCV piping. Can someone tell me what diameter the PCV pipe must be?
Since 16mm is the socket size, I assume the PCV pipe can be around 20mm or so.

What is the diameter of of the threaded part of the spark plug to know what thickness rope to use?

 

[eljefino]

You likely have 14mm diameter threaded plugs. Clothesline is good. I wouldn't bother with the PCV piping. Good luck!

 

[Trav]

Are these recessed plugs and you just want to use the PCV pipe as a guide?
Just measure the O.D. of the 16mm socket for the correct size. I would use nylon rope, its easier to work with getting it down recessed plug holes.

 

[JHZR2]

Wow, sounds like youre embarking on a neat job. Would love to see pictures of how you do this!

 

[shDK]

The last time i did it i drilled a hole an old sparplug. Screwed in a air pressure fitting and blew about 0.3-0.4 bar of air pressure into the cyllinder. That kept the valve in place.

 

[Chris142]

Originally Posted By: shDK
The last time i did it i drilled a hole an old sparplug. Screwed in a air pressure fitting and blew about 0.3-0.4 bar of air pressure into the cyllinder. That kept the valve in place.
i screwed an air fitting into an antifouler,screwed that into the plug hole and plugged my air hose onto it. worked great.

 

[Trav]

Originally Posted By: shDK
The last time i did it i drilled a hole an old sparplug. Screwed in a air pressure fitting and blew about 0.3-0.4 bar of air pressure into the cyllinder. That kept the valve in place.

Thats the accepted method but if you loose air pressure for any reason there goes the whole ball game if the stem seals doesn't stop the valve from falling in. .
The rope is safer and you can leave it as long as you like without fear of dropping a valve.

 

[expat]

I found that if the piston is at TDC on the cyl you are working on, the valve could not drop to the point where it could not be retrieved.

Just put a stick down the spark plug hole to make sure the piston is at TDC befor you remove the valve spring.

 

[eljefino]

The only thing about air pressure is if you get "wet air" for whatever reason that can fill up your cylinders. Do a purge/ turn it over without spark plugs when you're done. This will also make sure you have everything seated right.

I lost a valve keeper somehow... working in my driveway my valve spring compressor came apart and my spring and other little doohickeys flew off into the woods.

I left my air compressor running for hours while I went off to a junkyard for what I needed. Used clothesline at the junkyard.

 

[supton]

Would it make sense to insert some clothesline with it not at TDC, then bump it up a bit to wedge the valve "good and shut"?

 

[Trav]

Originally Posted By: expat
I found that if the piston is at TDC on the cyl you are working on, the valve could not drop to the point where it could not be retrieved.

Just put a stick down the spark plug hole to make sure the piston is at TDC befor you remove the valve spring.

Thats true, most engines wont allow the valve to go down that far. Sometimes for whatever reason the dam piston blows down.
I figure it wasn't exactly TDC or the valves were so close that while compressing the spring it touched the top of the piston.

Your right, its very rare but clothesline is safe and easier on the ears.

Originally Posted By: Supton
Would it make sense to insert some clothesline with it not at TDC, then bump it up a bit to wedge the valve "good and shut"?

Thats exactly how you do it but don't bump it with the starter, instead turn it with a ratchet, then back it up a slightly to get the line out.

 

[JHZR2]

Originally Posted By: Trav
turn it with a ratchet, then back it up a slightly to get the line out.


Thought you werent supposed to turn an engine backwards? I know its a tiny bit, but couldnt it cause a timing chain/belt slip?

 

[Trav]

If its an OHC the belt usually wont be on anyway because the cam(s) is removed, no cam no valve movement.
If its possible to remove the slipper (if used) without removing the cam (rare) turning it a few mm backward isn't going to slip the belt especially with no spark plugs in it.

Of course like anything there is always some sort of exception.

 

[expat]

Somebody once suggested filling the cyl with Grease.

Don't try this at home kiddies!