This last weekend My Son and I tried to adjust the rockers because of lifter noise and found that most of them are bottomed out for adjustment. So We have decided to Replace the Lifters with new ones. I have watched a few videos and am wondering if there is a trick to cleaning off the Varnish build up on the bottom of the lifters to allow me to get them out a little easier? Is there something I could add to the oil and run it for a while to loosen the Varnish coating on the bottom of the lifters? Any information would be greatly appreciated. Thanks in Advance.

JRB64

 

Marvel Mystery Oil...………...just trickle it over the lifters and let it sit for 24 hours or so....or a 50/50 mix of acetone & ATF works wonders as well

 

Thanks... I will give it a try..

 

Installing new lifters on a worn cam isn't a good idea. What year 300 are you working with? The 300 with hydraulic lifters doesn't need adjustment.

 

What does "they are bottomed out of adjustment" mean? Are they bolt down rockers or adjustable? If the old lifters are good I wouldn't take the chance of wiping the cam during new lifter break in.

To remove the old lifter take a small flathead screwdriver or pick screwdriver, stick it in the inside lip of the lifter and ram the lifter up and down. After enough rams it will start to come out. Vice grips may make it easier to finish them off.

Don't remember to soak new ones in oil, break them in with new break in oil, and recheck valve adjustment after. Again, make sure they are broken in properly.

 

I am working on a 1979 300 Six, and from what I am told by the local auto parts store this engine should have Hydralic Lifters. When I tried to adjust the lifters its like the adjustment nut in the Rockers on most of them were bottomed out. So from what I am seeing it looks to me like the lifters are stuck or the pistons inside of the lifters are stuck and not working properly. This is why I figured it would be better just to replace the lifters. So when you are talking about braking in the new lifters you mean run the engine at 2000 RPM for 20 Min? I am going to run Joe Gibbs 30 weigh Brake in Oil when I brake in the new lifters and I will put a good amount of Cam Brake in oil on the Cam lobes and the Lifters when I install the new ones. I will also soak the lifters in oil overnight before I install them into the Engine. The Studs on the Rockers looks just like any normal individual stamped rocker assembly that has a stud and an Adjustment nut that you install the Rocker On.

 

If this isn't a good Idea then should I just leave the bad lifters in the Engine and maybe open up the side panels and pour some Marvel Mystery Oil on top of the lifters and work them until they free up or am I in a position that I should Replace the Cam and Lifters in the engine? I would rather not tear the entire front of the truck apart to replace the cam if at all possible. If I was in that position I would probably take the entire engine out and have it completely Rebuilt. Intake Rocker on the Back of the motor is very loose but seems to be bottomed out in the Adjustment and that is where my noise is coming from in the valve train. There was a couple of other valves that were a little loose but not like the one on number six intake.

 

The valve train on these engines are hydrallic and are not adjustable as such.

If they need adjustment then you have to swap with longer or shorter push rods to make up the difference.

It's a pretty intensive proceedure to do this properly and requires the lifters to be bled down and compressed, and for the each cylinder to be aligned correctly in it's firing order for each adjustment.

After you compress the lifters, and have the engine in the correct position for each valve needed, you measure the clearance between the rocker arm and the valve stem tip with a feeler gauge. 0.125 to 0.175 is ideal, and allowable is 0.100 to 0.200.

 

i am in a similar situation on my 78 300, i would like to do the lifters and pushrods but im not sure if i have hydraulic. so when you put in new broken in lifters and pushrods all you have to do is tighten the rocker to torque and that's where it sits?

 

OK
1965 to 1984 300s have hydraulic lifters and stud mount adjustable rocker arms
1985 and later engines have hydraulic lifters and pedestal mount bolt down rocker arms. No adjustment

JRB64
You may not have a lifter problem.
If you continue to turn the adjusting nut it will pump out all the oil in the lifter till the plunger is bottomed out in the lifter.
You are just supposed to turn the nut till there is no longer any play in the pushrod and the plunger has barely moved down then the nut is turned another 1/2 to 3/4 turn.

Start with cylinder #1
Turn the crank clockwise till the exhaust valve just begins to open and adjust the intake valve.
Then continue to turn the crank clockwise till the intake valve just closes and adjust the exhaust valve.

Go on down the line adjusting the rest of the cylinders using the same procedure.

 

So, Maybe I am missing the point here but as I understand the Hydraulic Lifter, it has a spring in it and when you take the lash out of the Lifter by loosening the Stud Nut then tighten the Nut back down till you loose the Play in the Push Rod then tighten it another half to 1 Turn all you are doing is compressing the internal spring inside of the lifter. Is this wrong? Also when people talk about putting in longer Push Rods that absolutely makes no sense at all to me. When the Engine was put together and was running 100% from the factory the Push Rod was the right length. The only variable in a Hydraulic Lifter system is the Hydraulic Lifter, the push rod doesn't get any shorter unless its bent. Now if I have a Collapsed Lifter and its not pumping up or the spring is worn out then I could see that the adjustment stud could not have enough thread to properly adjust the Lifter. The only other variable would be if the Rocker Stud has somehow backed out as I have seen in Chevys that were pressed in studs and not screw in studs. Are the Studs in these Heads Press in or are they Screw in? Or I could have a bad Lobe on the Cam I guess. But the way this thing runs and the Vacuum readings I am getting from it I cant believe I would have a bad lobe on the Cam.

 

There is a piston inside the lifter that is held in with the spring clip you see inside the top of the lifter.
Once the pushrod is in place the spring under the piston pushes the piston up to the pushrod.
When the engine is running the oil under pressure fills the chamber under the piston and the spring no longer is needed.
A one way valve keeps the oil from backing out of the lifter so the lifter can maintain zero rocker arm lash.

The stock lifter piston has about .200" of travel.
Your job is to adjust the rocker arm and push rod so the piston is about .075" down from the top of the lifter which leaves plenty of piston travel in both directions to keep the rocker arm at zero lash.

Different pushrod lengths come into play when the engine has been modified for performance.
A rocker arm tip needs to travel across the center of the valve stem.
If the rocker arm sits too low the rocker tip will travel to the inside of the valve stem tip and if the rocker arm is too high the travel is to the outside.
The correct pushrod length is needed to position the rocker arm at the right heigth

Once a higher lift cam is installed and/or longer valves to accommodate the extra lift the geometry will no longer be correct with the stock pushrods length.
If you are working with the non adjustable pedestal mount rockers and they need to be shimmed to get the correct geometry then longer pushrods will be needed.
Just two examples.

 

In some of the intervening years between '65 and '84 there were 3/8 studs with a shoulder with a 5/16 nut. Those were designed to be torqued down tightly with no means of adjustment. Does your engine have studs with a 5/16-NF thread?

 

I can't be sure unless I take the Valve Cover back off to check. But I think that is exactly what I have. I watched my Son on the Wrench and as we were adjusting the valves it seemed they were all really tight as he was adjusting them.

 

I have decided to go back through and check all the adjustments on the lifters before I replace the Lifters with new ones. I think its worth checking before I put a new set of Lifters in that might flatten an old Camshaft and turn this into a lot bigger job than I really want.