bigvette1

Need some advice on this problem...

I am working on a 73-454 that has a Crane 272 cam (218/218, .500 lift, 112 LSA) not much.

Step 1 - After a rebuild I started having lifter noise. Inspection showed 2 rockers (Comp roller tip) had the rollers trashed. Ok, change to GM stamped steel again. Adjusted using the EO - adjust intake and IC - adjust exhaust, carefully spinning the push rod and 1/2 turn after preload. Engine ran well good vacuum just clack clack on several lifters.

Step 2 - Has a bad lifter so I replaced the lifters and the push rods with new parts, new rocker ***** and nuts. Used the EO-IC method, same clack clack on several lifters. PYO problem.

Step 3 - Installed new GM performance parts stamped steel rockers, checked push rods carefully and adjusted using the EO-IC method and same thing clack clack on several.

Step 4 - Took Lars paper on valve adjustments and adjusted using the every engine 1/4 turn adjust next in firing order. Engine runs well, good vacuum, pretty solid idle just clack clack clack. I was super careful on spinning the push rod in fact I went a tad tighter that just when it starts to resist.

What do you think of just cutting slots in an old set of valve covers and adjusting like old time with until noise, tighten till noise stops and +1/2 turn??


Ok, and ideas on this or am I chasing a problem that is not going to go away until a rebuild comes about. Thanks for the ear.

tonak

Cut valve covers works for me

7T1vette

The 'spinning the pushrods' method is misunderstood by lots of folks. First, you can only set the adjustments on those valves which are completely closed. The best way to do that is to rotate the engine until the valve you are setting opens, then closes...plus a little more just to make sure it is fully closed. Here is where I would alter the technique. Shake the pushrod up and down. If there is no 'slop' in the rod movement, you need to back off the adjustment nut until you get some freeplay (slop). Then, as you are shaking the pushrod, tighten the adjustment nut slowly until the slop disappears. This is the "zero lash" point on the lifter. Now, tighten the nut about 1/2 to 3/4 turn to put the lifter piston near the center of its travel. That lifter is now set properly.

Note: When you find the "zero lash" point with this method, you will notice that you can still easily turn the pushrod. But, if you try to spin it and let go of it, the rod will immediately stop turning as there is no "freeplay" left in the adjustment. This is what is very confusing to folks using the spin method...they don't really know when to detect the "zero lash" point.

Once you've adjusted all 16 lifters, put the valve covers back on--without tightening the bolts up yet--and start it up. You should not get any clacking with hydraulic lifters.

pws69

Very well articulated, '7T1' - difficult point to get across!

bigvette1

Many thanks for the advice. I'll try that to see where I am causing the clack....
Jim

billla

I would go back and check your valvetrain geometry and check for coil bind and all valvetrain clearances. I expect this is a lot less about valve adjustement, and more about a fundamental geometry/clearance issue.

As for how to adjust valves, I'll stick with Lars' approach that I've used successfully on a few hundred SBCs

Project80

Instead of cutting up a valve cover, you can pick up a set of oil keepers, either the plastic or metal type. It still gets a little messy.
Plastic type - http://www.amazon.com/Lisle-35500-Ro.../dp/B000COC8NQ
http://www.summitracing.com/parts/PRO-66822
I have a set of metal ones that are probably Snap-on, but it really doesn't matter. Actually, I don't use them, I set the valves by tightening until the play is gone and then turning it the other half to three quarter. I go by the original spec's for that motor. This was how I was taught by Bobby the Mechanic (at the Mobil station) just a few decades ago. Try going through the sequence again

zigvs

its a messy affair no matter what you do when the motor is running.I found every cr I had,had different preloads after zero lash.Also I found roller rockers have a tendency to need adjusting on a regular basis.And there noisy anyway.I love um