I have to disagree. If the pushrod is to long it will push the vavle stem down further and thus contact the stem closer to the intake.

I will check the preload and stem contact point with my stock and aftermarket 7.45's and decide what to do from there.



Fast and Easy Way to Check Hydraulic Lifter Preload when using Non-Adjustable Rocker Arms
With the cam, hydraulic lifters and pushrods in place, install your rocker arm assembly. Use the prescribed method in your repair manual and torque down all the valve train bolts in the proper sequence. Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)

Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now carefully remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.

Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020? to .060? apart you have proper lifter preload. If the lines are the same or less than .020? apart you have no or insufficient preload. If the lines are further apart than 060? you have excessive lifter preload. To bring your preload into tolerance, use one of the methods described in the next section if necessary, or call the Crane Tech Line for assistance (386/258-6174).

 

FWIW I've run an 02 Z06 cam in my 4.8 for almost a year now with stock pushrods, LS6 yellow springs and no issues.

 

I'm really not trying to argue here, but this is something I know I'm right on, trust me here man . What you are quoting (the first quote) and saying ONLY apply to adjustable rockers are the proper preload. The only way the stem contact could be different on these motors is if the longer push rods are too long and bottoming out in the lifter and actually holding the valve open. (not going to happen with only being .025 longer with the smaller base circle.

With these motors, the distance from the pivot point and the valve stem is FIX, it CAN NOT be changed. If it is, then the valve is not closed. You can go ahead a check it, but I'll lay a 20 dollar bill on it that it will be in exactly the same place with both push rods.

Your last quote from Crane is a great way to check the pre load, btw.

To be honest with you both your stock push rods and the .050 longer ones would work, as one set will be .025 less preload then stock and the other will be .025 more preload then stock.

I hope you get it fuigered out man

 

There is .090" travel in the lifter more preload will quite the valve train down but will hinder performance due to the additional drag. Less preload will produce a more valve train noise but decrease drag. Ideally you want .045" preload on the lifter.