Holding Valves Up
Thread Starter
Melting Slicks
Joined: Feb 2003
Posts: 2,330
Likes: 6
From: Long Island NY
Holding Valves Up
I'm going to do valve seals and I know the 2 ways to hold up the valves are air & rope. I'm leery on using air, but how much psi should be used? Since I'm going to at TDC the valve shouldn't fall in anyway, is rope better, if so about how much rope is put in at TDC?
Race Director
Joined: Jun 2000
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From: FL
I have done mine twice and all I do is put each cylinder at TDC in turn (using the firing order).
With the piston at TDC, the valve has maybe 1/2" to move max.
After it is a TDC, I feed a little rope in as a backup but have had no problems. I just feed in a couple of feet till I feel resistance.
With the piston at TDC, the valve has maybe 1/2" to move max.
After it is a TDC, I feed a little rope in as a backup but have had no problems. I just feed in a couple of feet till I feel resistance.
Burning Brakes
Joined: Jan 2001
Posts: 1,004
Likes: 16
From: Gainesville, Florida
I've used air a couple of times & it works great. I used the hose with spark plug fitting & air coupler that you can buy at any auto parts.
On the psi, the standard portable/garage compressor isn't capable of developing enough to exceed the normal pressures of a healthy motor/ combustion chamber anyway so I didn't concern myself with it. I think mine is set for 100psi but it probably takes a small fraction of that to hold a valve up.
I know it works but shoving rope into a engine cylinder is just a little too bubba for me.
On the psi, the standard portable/garage compressor isn't capable of developing enough to exceed the normal pressures of a healthy motor/ combustion chamber anyway so I didn't concern myself with it. I think mine is set for 100psi but it probably takes a small fraction of that to hold a valve up.
I know it works but shoving rope into a engine cylinder is just a little too bubba for me.
Last edited by gearheadz; May 17, 2005 at 10:14 AM.
Race Director
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From: Corsicana, Tx
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Call me lazy, but when I change springs etc...I never even pull plugs. I just put piston at TDC (look at balancer and watch valves). They can't fall very far and it works fine. No need for all the air and rope stuff.
JIM
JIM
Drifting
Joined: Sep 2004
Posts: 1,532
Likes: 4
From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark
Originally Posted by gearheadz
I've used air a couple of times & it works great. I used the hose with spark plug fitting & air coupler that you can buy at any auto parts.
On the psi, the standard portable/garage compressor isn't capable of developing enough to exceed the normal pressures of a healthy motor/ combustion chamber anyway so I didn't concern myself with it. I think mine is set for 100psi but it probably takes a small fraction of that to hold a valve up.
I know it works but shoving rope into a engine cylinder is just a little too bubba for me.
On the psi, the standard portable/garage compressor isn't capable of developing enough to exceed the normal pressures of a healthy motor/ combustion chamber anyway so I didn't concern myself with it. I think mine is set for 100psi but it probably takes a small fraction of that to hold a valve up.
I know it works but shoving rope into a engine cylinder is just a little too bubba for me.
Le Mans Master
Joined: Oct 2002
Posts: 5,714
Likes: 6
From: Silver City NM
St. Jude Donor '05-'07
Originally Posted by 427Hotrod
Call me lazy, but when I change springs etc...I never even pull plugs. I just put piston at TDC (look at balancer and watch valves). They can't fall very far and it works fine. No need for all the air and rope stuff.
JIM
JIM
But a good idea Jim!!!
Dep
Thread Starter
Melting Slicks
Joined: Feb 2003
Posts: 2,330
Likes: 6
From: Long Island NY
So then what's the main purpose of using air? Is it that you can do all valves without turning the crank? If so fine. I would rather go to TDC and change and adjust them at the same time...it sounds good to me, but I'm a novice at valves seals...
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Racer
Joined: Jan 2003
Posts: 383
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From: Columbia SC
You still have to go to TDC on every cylinder when using shop air. I have used the "air" method several times with no problems at all.
Pay attention to the other things you must do to complete this job properly. use the sleeve and lubricate the O ring.
Pay attention to the other things you must do to complete this job properly. use the sleeve and lubricate the O ring.
Burning Brakes
Joined: Jun 2002
Posts: 792
Likes: 2
From: Norcross GA
Originally Posted by Pete76Shark
You still have to go to TDC on every cylinder when using shop air. I have used the "air" method several times with no problems at all.
Bob
Melting Slicks
Joined: Jul 2001
Posts: 2,609
Likes: 12
From: Massapequa Park NY
Either method works, never thought about not using either & bringing each piston to TDC. With the air method it was pretty fast to loosen all the rockers, which closes the valves anyway, pull the plugs & pressurize each cylinder. Too much air will cause the crank to rotate, but it will stop at BDC. Then you need to be carefull not to drop a valve 
Jim
Jim
Drifting
Joined: Sep 2004
Posts: 1,532
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From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark
I pressurize till BDC "before" removing teh valve keepers so cylinder stays pressurized the entire time.
The air pressure simply holds the valves up. You can only do one cylinder (2 valves) at a time. Once you replace the valve stem guide seals or do whatever it is that you are doing, you move the air to the next cylinder and remove retainers etc till you get all 8 cylinders. Then I always adjust valves by starting the engine. We set PSI at 100, but really probably didn't need that much. You usually have to tap the top of the valve springs a time or 2 to get em loose (don't hit the valve) before you can break em loose with the valve spring compressor.
If you move cylinder to TDC, and don't remove the plug, are you just relying on cylinder pressure to hold up the valves? I don't see how you could compress the valve spring in order to remove the keepers without "something" holding the valves up. Not sure how the "rope" works either. Can somebody explain that to me? There is quite a bit of pressure on teh valve stem springs.
The air pressure simply holds the valves up. You can only do one cylinder (2 valves) at a time. Once you replace the valve stem guide seals or do whatever it is that you are doing, you move the air to the next cylinder and remove retainers etc till you get all 8 cylinders. Then I always adjust valves by starting the engine. We set PSI at 100, but really probably didn't need that much. You usually have to tap the top of the valve springs a time or 2 to get em loose (don't hit the valve) before you can break em loose with the valve spring compressor.
If you move cylinder to TDC, and don't remove the plug, are you just relying on cylinder pressure to hold up the valves? I don't see how you could compress the valve spring in order to remove the keepers without "something" holding the valves up. Not sure how the "rope" works either. Can somebody explain that to me? There is quite a bit of pressure on teh valve stem springs.
Drifting
Joined: Sep 2004
Posts: 1,532
Likes: 4
From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark
I've only seen two kinds. One is a large C-clamp looking thing and must be used with the heads off the engine. The other is the pry-bar that must be used in conjunction with the rocker stud.
Thread Starter
Melting Slicks
Joined: Feb 2003
Posts: 2,330
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From: Long Island NY
Race Director
Joined: Jun 2000
Posts: 10,029
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From: FL
Originally Posted by 70BBvert
Too much air will cause the crank to rotate, but it will stop at BDC. Then you need to be carefull not to drop a valve
Jim
Jim
I also have an ARP balancer bolt that has a 1/2" drive socket built in (yes it is a big bolt). Makes it really easy to turn the crank.
