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Valve lash adjustment question.

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Old Apr 2, 2007 | 11:08 PM
  #1  
jagevileye21's Avatar
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From: Detroit, MI
Car: 1991 Z28 Vert
Engine: LT1 350
Transmission: T56 6 Speed
Axle/Gears: 3.42 LSD
Valve lash adjustment question.

How can tell if the intake valve/exhaust valve is open or closed with the intake manifold on?

Nevermind, I answered it just by looking at them as I turned the crank. However, when exhaust valve is open, is it up or down?

Thanks in advance,
Jay

Last edited by jagevileye21; Apr 2, 2007 at 11:48 PM. Reason: I answered my own question.
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Old Apr 2, 2007 | 11:18 PM
  #2  
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From: Northern CA.
Car: '82 Z28
Engine: 350
Transmission: TH400 4,000 stall
Axle/Gears: Currie 9", 4.56 gears
Re: Valve lash adjustment question.

Since you're doing a valve lash adjustment, look at the valves.
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Old Apr 2, 2007 | 11:47 PM
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From: Detroit, MI
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Engine: LT1 350
Transmission: T56 6 Speed
Axle/Gears: 3.42 LSD
Re: Valve lash adjustment question.

I basically need to know...

When the exhaust valve is open, is it up or down?

Thanks,
Jay
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Old Apr 2, 2007 | 11:49 PM
  #4  
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Valve lash adjustment question.

When a valve is open, it's lifter and pushrod are up, and the valve is down.
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Old Apr 3, 2007 | 02:21 AM
  #5  
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From: Detroit, MI
Car: 1991 Z28 Vert
Engine: LT1 350
Transmission: T56 6 Speed
Axle/Gears: 3.42 LSD
Re: Valve lash adjustment question.

Thanks for the info.

How far do the pushrod usually go before the valve is fully open? Or does it depend on the cam & lifters?

This is my first time doing this and I just want to make sure that I adjust the valve lash correctly.

Thanks again,
Jay

Last edited by jagevileye21; Apr 3, 2007 at 02:55 AM.
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Old Apr 3, 2007 | 11:19 AM
  #6  
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Valve lash adjustment question.

The pushrod will move up by the amount of lobe lift on the cam when the valve is fully open.

To make it easier on yourself, make 4 marks on your balancer at 0, 90, 180 and 270 degrees. Turn the engine over to TDC and look at the position of the distributor rotor. If it's pointing at the #1 terminal, then you're at #1 TDC firing, and the #1 valves are both closed. If it's pointing to the #6 terminal, then you're at #6 TDC firing, and the #6 valves are both closed. Then turn the engine over to the next mark on the balancer, and lash the next cylinder in the firing order. If you started with #1, it's 1-8-4-3-6-5-7-2. If you started with #6, it's 6-5-7-2-1-8-4-3. Continue until you've done all 8 cylinders.
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Old Apr 3, 2007 | 01:30 PM
  #7  
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From: Detroit, MI
Car: 1991 Z28 Vert
Engine: LT1 350
Transmission: T56 6 Speed
Axle/Gears: 3.42 LSD
Re: Valve lash adjustment question.

Apeiron,

I using this method...

Adjusting Hydraulic Lifters for Proper Preload

In order to adjust the preload, the lifter must be properly located on the base circle or "Heel" of the lobe.

At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Remove the valve covers, and pick a cylinder that you are going to set the preload on.

2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)

4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at "Zero Lash". Turn the adjusting nut down one half to one full turn from that point. Lock the adjuster into position. The intake is now adjusted properly.

5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.


Question

When I use this method and I tightened the rocker arms 1 full turn the rocker arms still had some play in them. Is this correct/normal?

Thanks for the help,
Jay
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Old Apr 3, 2007 | 01:35 PM
  #8  
Apeiron's Avatar
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From: Mercedes Norte, Heredia, Costa Rica
Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Re: Valve lash adjustment question.

That method works fine, too. It doesn't require you to put the engine in any particular position, but it involves more turning of the crank.

When you've got the valves lashed, there can be some side-to-side motion of the rockers on the valve stem, but there will be no up-and-down motion.
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Old Apr 3, 2007 | 02:45 PM
  #9  
jagevileye21's Avatar
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From: Detroit, MI
Car: 1991 Z28 Vert
Engine: LT1 350
Transmission: T56 6 Speed
Axle/Gears: 3.42 LSD
Re: Valve lash adjustment question.

Yeah, there is only alittle side to side motion.


Thanks again,
Jay
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Old Apr 5, 2007 | 07:44 PM
  #10  
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From: Kempner,TX,
Car: 1996 Vette / 1992 GSX1100F Suzuki
Engine: 1996 Corvette Coupe 388 LT1 (+.060)
Transmission: Auto
Axle/Gears: 3.07
Re: Valve lash adjustment question.

Originally Posted by jagevileye21
Apeiron,

I using this method...

Adjusting Hydraulic Lifters for Proper Preload

In order to adjust the preload, the lifter must be properly located on the base circle or "Heel" of the lobe.

At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.

1. Remove the valve covers, and pick a cylinder that you are going to set the preload on.

2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder's intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)

3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)

4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at "Zero Lash". Turn the adjusting nut down one half to one full turn from that point. Lock the adjuster into position. The intake is now adjusted properly.

5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.

6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.


Question

When I use this method and I tightened the rocker arms 1 full turn the rocker arms still had some play in them. Is this correct/normal?

Thanks for the help,
Jay
YEP, YOU NAILED IT! Excellent info for him.

The only thing I do differently is to move the pushrod up and down, rather than twist it, feeling for slight resistance.

I'm so ham-fisted that "slight resistance" can become a little difficult to determine for me, especially after adjusting six or eight lifters. So I simply move the pushrod up and down as I tighten the adjusting nut. I continue until all pushrod play is JUST eliminated. More than one way to skin a cat.

Jake
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