1976 - valve stem seal replacement - airflow from pressurized spark plug hole (1 Viewer)

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Atlanta
My 1976 FJ40 has been smoking blue smoke since I bought a month or so ago. I'm replacing valve stem seals with a compression tool for the springs and pressurizing the spark plug holes to 80 psi. Once I figured out the process it was going pretty smoothly but when I got to plug 4, and a lesser extent #5, I have faint airflow from a port on the top of the head. I circled it below in yellow. Anyone know what this is and if I should be feeling air when pressurizing the spark plug hole? Any thoughts on if it is normal or a sign of another issue?

I remind myself that chasing these things are the fun part.

valves_LI.jpg
 

pb4ugo

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Did you do a wet & dry compression test b4 you you decided to do valve seals? This would narrow down where and why you are burning oil, valves, rings, head gasket, etc . Essentially you are doing a cylder leak down test while you are replacing the valve seals. All the valves are closed. The hole you are getting air from is the oil drain to the crank case for the cylder head. What you are experiencing is air going past the rings and flowing into the crankcase then ou that hole . When you are finished replacing the seals, do a dry and wet compression test. It may also be the piston is at the bottom of the cylder where the rings would be less effective because of possible cylder wall taper from wear.
 
Joined
Dec 19, 2020
Messages
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Location
Atlanta
Did you do a wet & dry compression test b4 you you decided to do valve seals? This would narrow down where and why you are burning oil, valves, rings, head gasket, etc . Essentially you are doing a cylder leak down test while you are replacing the valve seals. All the valves are closed. The hole you are getting air from is the oil drain to the crank case for the cylder head. What you are experiencing is air going past the rings and flowing into the crankcase then ou that hole . When you are finished replacing the seals, do a dry and wet compression test. It may also be the piston is at the bottom of the cylder where the rings would be less effective because of possible cylder wall taper from wear.
Ahh, makes sense. I did a dry compression test before starting the seals. They are:

1 - 140
2 - 135
3 - 150
4 - 142
5 - 145
6 - 155

I'll do another dry and a wet one afterwards.
 
Joined
Jan 17, 2005
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Southern Colorado
Nothing wrong with those compression numbers. You could also just have a carbon chunk temporarily stuck in the valve seat that fell off when you removed the spark plug. I wouldn't lose a lot of sleep over this.
 
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Northwest Washington
What did your old and new valve seals look like? I’m trying to do this now and confused on how the “new style are supposed to work? the new one is the shorter one, the old is built into the spring cup.

sorry for the hijac, thank you for any help.

F2963D16-1F5F-4531-8EE3-203E48CDF26E.jpeg


F0BCA341-2B35-49B0-9FA5-87A9AF25D7CA.jpeg
 
Joined
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Atlanta
When I got in there my old ones looked just like my new. Remember to spread a little oil on the opening and then just slide it on. I gave it a very gentle tap with a deep socket to make certain it was seated. Not too hard or it can bust (spring pop off) and you'll only have 11 new ones. Found that out the hard way.
 
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Mine didn't have the seat at the bottom. I have a '76 2F motor. Pic of the old stem seal.


valve (2).jpg
 

turdfurguson

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I went through this with my 76. Rebuilt the head and tried two different valve seal types because of smoking issues. I also had excellent dry compression numbers so it was very confusing, but the final solution was new rings and cylinder hone. After that, no a bit of smoke and perfect compression . My oil now stays noticeably cleaner due to the lack of blow by. We ended up using the newer style valve seals and my machinist cut the bottoms off of the old valve seals to act as a spring seat. Weird solution, but it worked well.
 

Dizzy

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Mine didn't have the seat at the bottom. I have a '76 2F motor. Pic of the old stem seal.


View attachment 2664467
The piece under the old seal isn't fixed in position, it comes off. Not a bad time to clean it. I stuffed rags down the holes for the oil return, and pushrods, but, only after I had to retrieve one of the keepers with a skinny pencil magnet, not fun.
 

turdfurguson

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Also, my oil rings were collapsed and full of carbon. Thus, the compression was good, but the oil scraping was not effective and causing smoking. It took a while to figure out.
 

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