Using compressed air to hold valve in place

[54olds]

Quick question - I need to remove my valve springs on my 324 Rocket engine to inspect the valve stem seals. I used my compressor to pressurize the cylinder, but it seems to keep putting in air and doesn't stop.

Is this normal, or should it fill up and stop?

[Eddie Hansen]

Originally Posted by 54olds

Quick question - I need to remove my valve springs on my 324 Rocket engine to inspect the valve stem seals. I used my compressor to pressurize the cylinder, but it seems to keep putting in air and doesn't stop.

Is this normal, or should it fill up and stop?

I did do this on my pontiac 400, with the sparkplug type fitting, it really didn't leak much at all, perhaps the valves are not closed? I am trying to remember where the timing was suppose to be I am sure I rotated until the piston was at the top, etc to ensure the valves were closed. sorry to not be more help....

if done properly it is NOT suppose to leak

[Olds64]

I have heard of using nylon rope in the cylinder when taking the valve springs off. I guess you feed it into the cylinder through the spark plug hole and then turn the engine by hand so the nylon rope coils up in the combustion chamber and keeps the valve in the head. I don't know if it works. It seems like I heard this from a friend that had to do valve guide seals on his Ford 5.0

[redoldsman]

Assuming the valve are closed, it should fill up pretty quick. You will probably still have some leakage past the rings but the amount of air flowing should show down pretty quick. Obviously and older engine will leak more past the rings if it has not been rebuilt.

[Rallye469]

I've used the nylon rope method 3 times...never had a problem.

I'm always afraid that if you push a valve down a bit...the air would
rush past and suck it down (using the air method).

[54olds]

How much rope should you feed into the cylinder, and how do you determine whether the valve is fully closed or not?

[Olds64]

You can determine if the valves are fully closed by taking off the spark plug and kicking the engine over with the coil wire off. Just hold your finger over the spark plug hole and have a buddy turn the engine over slowly. Then when your finger is pushed off by the compression you know you are near the right spot. Finally, use a flash light and peer down in the cylinder and have a buddy move the engine with a big wrench on the crank snout. You can see when the piston is at the top of the stroke. That is TDC.

With the nylon rope method I think you just feed as much into the cylinder as will fit.

[442Harv]

JUst did this on a Chevy PU. If you loosen or take off the rocker, both intake and intake, it does not make a difference where is piston is. Mine worked great, changed all the valve seals.

[Warhead]

Both ways work WELL.

I am, however, unnerved when the cylinder pressure starts pushing down the piston-rotating the engine when I least expect it.

I usually will do the rope method, now. A foot or two of rope, and crank the engine by hand lightly, to keep valves snug.

BTW, how much air needs to go in to keep it tight???

[442Harv]

I use a 100 pounds air. What I like about the aire, is you do not have to turn the motor if you are,like doing valve seal on all cylinders. If you are just doing one cylinder, like one valve spring, then the rope may be easier. Alsao if you use air, it will rotate the engine.

[Warhead]

Originally Posted by 442Harv

I use a 100 pounds air. What I like about the aire, is you do not have to turn the motor if you are,like doing valve seal on all cylinders. If you are just doing one cylinder, like one valve spring, then the rope may be easier. Alsao if you use air, it will rotate the engine.

I was asking about how bad 64 Olds's leakdown was, I can see you have done this a few times too.