Am I understanding this correctly....
Thread Starter
Melting Slicks
Joined: Mar 2008
Posts: 2,300
Likes: 1
From: Quincy IL
Am I understanding this correctly....
'85 L98 Stock cam ...hydrolic lifters.... replaced with a stock cam, new lifters and new push rods.
Just a couple questions after studing all your advise.... As near as I can tell from hours for reading ... Lifter Preload is tightening down the rocker arm nut until there is zero lash from the pushrod/valve... then 1/2 to 3/4 turn. Do this with the engine cold. 1/2 turn adjustments can be made if necessary to remove clatter when the engine is running after the 20 minute 1,800 - 2,500 rpm break in. That all makes sense to me. Now my big question...is there a specific order to obtaining the preload... maybe the firing order ? ? ? Does the cam have to be in a specific position per cylinder or do I not move the cam once I am on TDC on the compression stroke cylinder 1. Thank you again.... very much.
Just a couple questions after studing all your advise.... As near as I can tell from hours for reading ... Lifter Preload is tightening down the rocker arm nut until there is zero lash from the pushrod/valve... then 1/2 to 3/4 turn. Do this with the engine cold. 1/2 turn adjustments can be made if necessary to remove clatter when the engine is running after the 20 minute 1,800 - 2,500 rpm break in. That all makes sense to me. Now my big question...is there a specific order to obtaining the preload... maybe the firing order ? ? ? Does the cam have to be in a specific position per cylinder or do I not move the cam once I am on TDC on the compression stroke cylinder 1. Thank you again.... very much.
Last edited by vette54728702; Feb 22, 2009 at 09:10 PM.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
As I written so many times I've lost count, the most critical part of setting lifter preload is making sure that the lifter your adjusting is on the base circle of the camshaft lobe.
Most of the problems that guys have when setting lifter preload is because they set it with the lifter on the ramp of the cam's lobe and not the base circle.
If you check the Tech Tips section on this Forum, you'll find the step by step instructions on how I, the big cam companies like Crane and CompCam and other guys do it. It's referred to as the Exhaust Opening (E/O) Intake Closing (I/C) method.
You DON'T WANT to set the lifter preload on a NEW cam with the engine idling. The engine should immediately be brought up to 2500 RPMs or so. Revved up frequently to allow oil spray to hit different locations but NO idle time.
Letting the engine idle while adjusting the lifter preload can kill the cam.
Be sure to use a bottle of Engine Oil Supplement (EOS) from a local GM dealer because it has additives that help prevent failure during break-in.
Also, for flat tappet cams, it's recommend that you use an oil that still has the necessary amount of zinc - I believe it's called ZDDP -; oil like Rotella.
Oil formulas have changed and the zinc was reduced to the point that many who are running flat tappet cams are experiencing cam failure - wipes lobes.
Hope this helps.
Jake
Most of the problems that guys have when setting lifter preload is because they set it with the lifter on the ramp of the cam's lobe and not the base circle.
If you check the Tech Tips section on this Forum, you'll find the step by step instructions on how I, the big cam companies like Crane and CompCam and other guys do it. It's referred to as the Exhaust Opening (E/O) Intake Closing (I/C) method.
You DON'T WANT to set the lifter preload on a NEW cam with the engine idling. The engine should immediately be brought up to 2500 RPMs or so. Revved up frequently to allow oil spray to hit different locations but NO idle time.
Letting the engine idle while adjusting the lifter preload can kill the cam.
Be sure to use a bottle of Engine Oil Supplement (EOS) from a local GM dealer because it has additives that help prevent failure during break-in.
Also, for flat tappet cams, it's recommend that you use an oil that still has the necessary amount of zinc - I believe it's called ZDDP -; oil like Rotella.
Oil formulas have changed and the zinc was reduced to the point that many who are running flat tappet cams are experiencing cam failure - wipes lobes.
Hope this helps.
Jake
