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Valve Stem replacement


TheNewbie

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Hello, 

 

   So I bought an 86 Z24 hardbody and it burns oil. It only really does it when I accelerate and shift. I replaced the PCV valve and it didn't help. I have never done valve work but I know that the stem seals are bad. When I pull the header and put the new seals on, do I have to do any type of valve adjustments or can I just replace the spring and move on? Also, is there a way to keep the valves from falling into the cylinder without using an air compressor or rope? Thank you.

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Could be rings if on acceleration. Intake vacuum is very low when accelerating so it won't suck much oil down the stem. Also the rings are thrust against the cylinder walls sealing the oil out of the combustion chamber... but when you let off to shift, the rings relax and the cylinder vacuum goes up.

 

If you shut it off and hours later or over night and you get a big poof of blue smoke the next time it's started, this is a better indicator of worn valve guides or seals... or both.

 

As the seals are cheap and easier to change than rings, it won't hurt to do them and see if it helps.

 

Removing the head is only way, other than compressed air or rope. Rope is the simplest and most reliable. You don't need electricity or a compressor and you could do it on the side of the road, leave it over night and finish it later.

 

 

Remove the two rocker arm shafts, complete with their rocker arms. All valves will now be closed.

Remove all spark plugs. Keep track of intake and exhaust side they are different.

Get about 3 feet of 3/8" nylon rope and tie a loop or a large knot in one end to preclude it ever dropping into the cylinder.

Slip it into the first cylinder. If it won't all fit, turn the engine forward or back to lower the piston using the 27mm nut on the front of the crankshaft..

Now turn the engine by hand using a 27mm wrench on the crank pulley nut until it stops.

 

The rope is now crushed into the combustion chamber and the two valves cannot move.

 

Use your favorite method of compressing the two valve springs, remove the keepers and spring retainers and pry the old seal off and replace.

 

Back crank up 1/2 turn and retrieve the rope.

 

Go to the #4 cylinder and do it. Then the other two any order.

 

 

Nothing has changed, only the seal, so valve lash will remain unchanged. Never hurts to check the lash if you haven't in the last 12 months or 15K miles whichever is first. Always check on a HOT engine. Both are 0.012"

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Pistons are 89mm and only need replacing if they or the bore is damaged and it needs to be bored out to an over size. Z24 mains  are the same as the L20B, Z20, Z22 engines and the rod bearings are the same all the way back to the L16 engine and ahead to the KA engines.

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