How to check blueprinting clearances with hydraulic lifters?

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dibbons

dibbons

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With hydraulic valve lifters and using a couple of adjustable pushrods, I understand I can take up the slack in the valve train with my adjustable rocker arms and measure for proper length pushrods-no problem.

What I don't understand, is this:

When I assemble the motor and place clay on the piston domes, if I had solid lifers I would just set zero lash and turn the engine over two spins. Then measure the clay-no problem.

However, since i have hydraulic lifters, I notice I can press the down on the pushrod end of the lifter with my finger. I guess there is a light spring inside that allows for a lot of down movement. When I assemble the cylinder heads to the short block and check for clearances with the clay (after setting zero valve lash again), When I turn the motor over a couple of spins, I imagine the resistance of the valve springs is going to push that lifter plunger down (maybe to the bottom of its travel?) and throw my piston to valve (and piston to cylinder head) readings way off.

Even if I had a couple of solid lifters for checking piston to valve clearance, I believe the effective length of the solid lifter differs from the hydraulic lifters, so that would also throw my readings off. I can't picture in my mind how to get around the fact that the hydraulic lifter plunger won't stay put in one place during my attempts at checking clearances.

Maybe I am over-thinking this procedure, but I can't afford to have things all bent up on the initial start-up, if you know what I mean. The motor is a small block 340 and I am using a custom hydraulic camshaft, Lunati hydraulic lifters, open chamber cylinder heads, and factory 273 adjustable rocker arms. Thank you for your advice/input.
 
This was told to me by a guy that builds engines, take the lifter apart and take out the piston and fill it with grease so it wont collapse. I found this to be a pain and a mess so sense I have a lathe I make a solid piece of aluminum that fit inside the lifter, installed the top and snap ring and it is solid, making your reading more accurate. It work great for me.
 
A ball bearing under the plunger cup or a nut? Whatever it takes to get the clip back on top of the plunger so it makes a solid lifter.
 
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Check piston to valve with a solid lifter, or hydraulic modified to be solid. Set some marks to check the rocker sweep at the same time. When the rest is all done, check the pushrod length with the hydraulic as it runs. Measure the preload by the distance between the top of the plunger and bottom of the retaining clip.
 
You put some very light valve springs on there. As long as they are weaker than the springs inside the lifters, this will work. Several cam companies make such springs.
 
That won't push the clay down on top of the piston. Lifter will still collapse.
 
There is no way the spring inside the lifter is stiff enough, you need to lock it up.
 
Put in some very light springs from the hardware store on 1 cylinder in place of the valve springs. (Or pay more for the same thing when they are called 'checking springs' LOL). Pump up that set of lifters with oil by pumping the plunger down and releasing for several cycles while immersed in motor oil in a can, and the plunger should stay 'solid' and open up the valves with the light springs easily. Go to town with your clearance checks; just watch that the plunger stays fully up when the valve mooshes into the clay.

If you have a setup where you are pretty confident that you have good valve-to-piston clearance anyway, just put in the light springs, omit the clay, and then rotate the crank 5-10 degrees at a time, + and - around TDC. Stop at each point, push down the valves with your fingers and measure how far they go down. If, at every point of measurement, both valves' movement exceeds the maximum valve lift due to the cam plus the desired minimum piston-to-valve clearance, then you know you will be good to go. (You will be in the clear with this method, but won't know the actual minimum clearance.)
 
Just use a 273 lifter and pushrod with the adjustable rocker arms at zero lash to check for clearance...
 
Many types of lifters have different lengths, however so slight. I’ll tell you what I did and it is fool proof:

Measure effective length of the lifter. This is from the lifter face to the cup where the pushrod sits. To do this you need a slide caliper and a ball bearing. The ball bearing must be as close to the diameter of the pushrod you’ll be using. Measure the diameter of the bearing and place the bearing into the lifters cup. Measure from the lifters face where the cam rides to the top of the ball bearing. Subtract the ball bearing diameter. Subtract the optimal lifter preload amount. Now you have the effective lifter length, including preload.

Obtain, make, or rent a “checking lifter”, to do this you must disassemble the lifters guts and and keep the cup part. Find a nut and bolt that will fit inside the bore of the lifter nicely, preferably fine thread. Drop the nut inside the bore. Thread in the bolt. Put the cup on top. Turning the bolt will allow you to change the effective length so the cup moves inward/outward. Cut the bolt If it’s too long. Epoxy the cup to the bolt and use your fingertip to make adjustments, only if this is a spare lifter.

Use your measurements and use the ball bearing again to make the checking lifter the exact size as your original lifters. Now you have a solid lifter that is the exact effective length and includes lifter preload. Score or mark a line on the cup and lifter to make it easier to see if the cup has shifted position and changed the length.

Now you can check piston to valve clearances, measure for pushrods, and check the sweep of the rocker over the valve tip.

When adjusting the pushrod, always keep the lifter end stationary, you’ll badjusting the rocker side. This will keep the checking lifters guts from adjusting as the pushrod expands and puts pressure on the checking lifter.
 
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69_340_GTS said:
You need less clay or softer clay? How about no clay... just use a dial indicator and measure clearance directly?
Click to expand...


The problem with checker springs is you always end up with way more p/v clearance. It's not very accurate. The valve train needs to see spring load to determine p/v.
 
install a solid lifter, it will not change your readings at the valve!! also, I use light checking springs. I have found, the difference between light springs vs, light affects valve lift by about .020. the light spring shows tighter clearance. the valve spring causes deflection. which changes your results. our cams are so big on duration, no cutting valve notches, use to get close clearances, then installed valve spring, and had more clearance. keep it simple!!!
 
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