Motor running rocker adjustment
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,972
Likes: 243
Motor running rocker adjustment
I set my rocker lash the way I always have, cam lobe on base circle, tighten down till I can’t spin the pushrod with my fingers and plus 1/2 turn. It’s not failed me before. However, I’m getting some light tapping at idle that I can hear in the car, it’s not much and may be within the realm of normal for a roller rocker but is enough that I’m willing to try to set it again. I’ve never had a problem with this method before but one difference is that I did this on a motor that hadn’t run in more than 6 months. In fact, the lifters were in baggies with a little oil for months. I think maybe they bled down and we’re adjusted in a bled down state. Sound feasible?
Would like to try to adjust them while running. Do I need to run it all the way up to temp and have hot oil or can I just start it up cold and get to adjusting? My plan is to back off the poly locks until I hear it tapping, cinch it down till it stops then add 1/2 turn. Obviously adjusting one at a time. Would you do anything different?
94 LT1
stock lifters
smallish Comp cam
guide plates/hardened PRs
Comp Pro Mag 1.6 RR (which I’ve read can be somewhat noisy rockers)
Prior to the cam, I ran Scorpion 1.7RR which had the normal sewing machine noise - no tapping.
Would like to try to adjust them while running. Do I need to run it all the way up to temp and have hot oil or can I just start it up cold and get to adjusting? My plan is to back off the poly locks until I hear it tapping, cinch it down till it stops then add 1/2 turn. Obviously adjusting one at a time. Would you do anything different?
94 LT1
stock lifters
smallish Comp cam
guide plates/hardened PRs
Comp Pro Mag 1.6 RR (which I’ve read can be somewhat noisy rockers)
Prior to the cam, I ran Scorpion 1.7RR which had the normal sewing machine noise - no tapping.
Le Mans Master
Joined: Feb 2005
Posts: 6,485
Likes: 566
From: Clearwater Florida
..... 
….. tighten them slowly ... they'll warm up faster than you can adjust them … oil control is helpful … use a piece of stiff laminated paper long enough and 4-5" high between the springs and valve cover rail on the head (I get ads all the time in the mail) … this'll keep oil off the headers … some rockers will let you use pushrod oil hole stoppers and some won't … use them if you can …..
….. tighten them slowly ... they'll warm up faster than you can adjust them … oil control is helpful … use a piece of stiff laminated paper long enough and 4-5" high between the springs and valve cover rail on the head (I get ads all the time in the mail) … this'll keep oil off the headers … some rockers will let you use pushrod oil hole stoppers and some won't … use them if you can …..
Last edited by C409; Jun 18, 2020 at 09:19 PM.
Drifting
Joined: Jul 2004
Posts: 1,356
Likes: 291
From: MA
I was in the same boat as you. Rebuilt the top end of the motor over the winter adjusted the rockers cold (zero lash then a half turn).
I have been running it now in the nice weather and the valve train was a bit noisey.
I took the valve covers off and cut some aluminum flashing about 18" long and 4" high and placed them inside the head towards exhaust (just laid them in there). This kept most of the oil off the headers.
Then I backed off the polylock until I heard the clacking, tightened the polylock until the clacking went away then gave it another half turn.
I aslo like to tighten the set screw in the middle of the polylock then turn the polylock nut counterclockwise very slightly to jam it against the Allen. This way nothing will loosen and the setting will stay.
I have been running it now in the nice weather and the valve train was a bit noisey.
I took the valve covers off and cut some aluminum flashing about 18" long and 4" high and placed them inside the head towards exhaust (just laid them in there). This kept most of the oil off the headers.
Then I backed off the polylock until I heard the clacking, tightened the polylock until the clacking went away then gave it another half turn.
I aslo like to tighten the set screw in the middle of the polylock then turn the polylock nut counterclockwise very slightly to jam it against the Allen. This way nothing will loosen and the setting will stay.
Last edited by grandspt; Jun 19, 2020 at 05:19 AM.
Drifting
Joined: Jun 2018
Posts: 1,402
Likes: 287
From: Brisbane Australia
C4 of Year Finalist (performance mods) 2019
This from comp cams for hydronic lifters
When the exhaust valve just begins to open on the #1 cylinder, adjust the #1 intake valve by loosening the adjusting nut slightly while spinning the pushrod until you feel lash in the rocker arm. Tighten the adjusting nut until the slack is taken out of the rocker arm and pushrod. Lightly turn the pushrod with your fingers as you tighten the adjusting nut, and you should feel a point where there is a little resistance. This is called zero lash – the point where you have taken all of the excess slack out of the pushrod. Turn the adjusting nut ½ turn past this point, giving you optimal pre-load for the rocker arm, pushrod and lifter. Follow this procedure by carefully adjusting each intake valve according to cylinder firing order.
Next, we’ll adjust the exhaust valves. To do so, you need to turn the engine over until the intake pushrod moves all the way up. Rotate just past maximum lift, where the intake will begin to close. The lifter is now at the base circle, and the exhaust valve can be adjusted. Note: DO NOT go too far down (over halfway) past the point of maximum lift. If you go too far, you will be in the overlap cycle – where intake valve lash is being taken up as the exhaust valve begins to open.
Rotate the exhaust pushrod with your fingers and begin to tighten the exhaust adjusting nut. When you begin to feel resistance against the pushrod, you are once again at zero lash. Tighten the adjusting nut another ½ turn. DO NOT OVERTIGHTEN. Repeat through the firing order until the lash on every exhaust valve has been set.
Now it’s time to double check, starting with cylinder #1. When the exhaust begins to open, check the intake. New hydraulic lifters shouldn’t be pumped up yet, so you should be able to spin the pushrod with some resistance. Think of the hydraulic lifter as a shock absorber – and you want to be right there in the middle of it. Until you have oil pressure, you’ll be able to push the lifter plunger into the bottom of the lifter. At that point, the lifter becomes solid. It might help to mark each rocker that has been set and then mark again each one that has been checked, giving the ones that are 100% finished a big “X” on the rocker arm body.
This is how I set them
When the exhaust valve just begins to open on the #1 cylinder, adjust the #1 intake valve by loosening the adjusting nut slightly while spinning the pushrod until you feel lash in the rocker arm. Tighten the adjusting nut until the slack is taken out of the rocker arm and pushrod. Lightly turn the pushrod with your fingers as you tighten the adjusting nut, and you should feel a point where there is a little resistance. This is called zero lash – the point where you have taken all of the excess slack out of the pushrod. Turn the adjusting nut ½ turn past this point, giving you optimal pre-load for the rocker arm, pushrod and lifter. Follow this procedure by carefully adjusting each intake valve according to cylinder firing order.
Next, we’ll adjust the exhaust valves. To do so, you need to turn the engine over until the intake pushrod moves all the way up. Rotate just past maximum lift, where the intake will begin to close. The lifter is now at the base circle, and the exhaust valve can be adjusted. Note: DO NOT go too far down (over halfway) past the point of maximum lift. If you go too far, you will be in the overlap cycle – where intake valve lash is being taken up as the exhaust valve begins to open.
Rotate the exhaust pushrod with your fingers and begin to tighten the exhaust adjusting nut. When you begin to feel resistance against the pushrod, you are once again at zero lash. Tighten the adjusting nut another ½ turn. DO NOT OVERTIGHTEN. Repeat through the firing order until the lash on every exhaust valve has been set.
Now it’s time to double check, starting with cylinder #1. When the exhaust begins to open, check the intake. New hydraulic lifters shouldn’t be pumped up yet, so you should be able to spin the pushrod with some resistance. Think of the hydraulic lifter as a shock absorber – and you want to be right there in the middle of it. Until you have oil pressure, you’ll be able to push the lifter plunger into the bottom of the lifter. At that point, the lifter becomes solid. It might help to mark each rocker that has been set and then mark again each one that has been checked, giving the ones that are 100% finished a big “X” on the rocker arm body.
This is how I set them
Last edited by GregMartin; Jun 19, 2020 at 08:20 AM.
Thread Starter
Drifting
Joined: Aug 2009
Posts: 1,972
Likes: 243
^^^pretty much the process I did when I put the top end back together.
I pulled the covers this morning and adjusted with motor running. I had to really back off the poly lock to make the rocker I was working on LOUD so I could be sure that what my ears were tuning into was in fact the rocker I was attempting to adjust. It ain’t easy to single them out especially once the fans kick in. Cardboard kept the oil at bay. I think I got them a good bit quieter, no random loud ticks. But these rockers are just a little more clattery than my last set - nature of the beast I suppose. I have it all back together but haven’t run it again with the covers on and hood closed - I needed a break, but I’m sure with everything reassembled and the hood closed I won’t hear clicking and clacking but rather just the normal mechanical sound of roller rockers.
I pulled the covers this morning and adjusted with motor running. I had to really back off the poly lock to make the rocker I was working on LOUD so I could be sure that what my ears were tuning into was in fact the rocker I was attempting to adjust. It ain’t easy to single them out especially once the fans kick in. Cardboard kept the oil at bay. I think I got them a good bit quieter, no random loud ticks. But these rockers are just a little more clattery than my last set - nature of the beast I suppose. I have it all back together but haven’t run it again with the covers on and hood closed - I needed a break, but I’m sure with everything reassembled and the hood closed I won’t hear clicking and clacking but rather just the normal mechanical sound of roller rockers.
Drifting
Joined: Nov 2015
Posts: 1,714
Likes: 331
Finalist 2020 C4 of the Year - Unmodified
Check the FSM as well, '87 L98 calls for a full turn after zero lash.
I don't get all finicky about zero lash, it's a tiny smidge of a turn from almost no movement to difficult to twist. A full turn after that is a huge difference. Key is be consistent. IMHO, of course.
I don't get all finicky about zero lash, it's a tiny smidge of a turn from almost no movement to difficult to twist. A full turn after that is a huge difference. Key is be consistent. IMHO, of course.
Advanced
Joined: Jun 2020
Posts: 52
Likes: 2
From: SW Nevada
Back in the day we adjusted hydraulic lifters while the engine was running all the time. Yes we did it with the engine at normal operating temp. We didn't listen for clatter. We backed off the nut until the engine started running rough (missing) then slowly tightened until the engine smoothed out again. Then tighten one half turn. Doesn't take nearly as long that way. Reinstall valve covers and clean up the mess.
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