i just installed a good used small block hydraulic cam in my 340 and all the lifters are rock hard,cant set my preload? do i have to remove all the lifters and drain them somehow or is there an easier solution?

It doesn't really matter if they are pumped up, what are you using for rocker arms?

Guessing they are adjustable at the pushrod side, so you can figure lifter preload by thread pitch and turns.

Well i have comp rollers which are adjustable but was kinda hoping to just use stock setup as this is a resto car.....

On a stock type setup I would set it up with the shaft and a couple of rockers (to measure an intake and an exhaust)

Bring to zero preload on base circle, zero dial indicator on pushrod side and torque down the shaft.

You can watch the lifter bleed down with spring pressure against it and dial indicator movement = lifter preload. (at which point you can order correct length pushrods if needed)

Repeat on a few other valves to verify consistent readings and that bank to bank is the same.

On a "stock" non-adjustable setup you just install the things and go.

On a set with adjustable rockers you bolt the rockers down with the adjusters backed out. Get each lifter on the base circle and adjust to zero lash (you can do this by spinning the pushrod - when it hits zero it will be tight to turn) then turn the adjuster an additional turn and tighten the lock nut.

Don't worry about the lifters being pumped up, they'll bleed down under spring pressure.

thanks for info guys,I must have been overthinking this,i was worried the valves might hang open or something.this engine will sit a month or so before I actually fire it.....

if i use my adjustable rockers whats the current thoughts for preload,1/4 turn,1/2 turn?

Adjusters are at the pushrods and 3/8-24? If so that's .041 per turn. I would personally go for 2 turns and .080 preload (but I would guess others think that's too much.)

Amount of preload is insignificant until you start floating valves, then it gets serious real fast. If you want to play it safe then less is more. 1/4-1/2 turn is sufficient. A few thousandths is all that's required.

I use between 1/8 turn to 1/2 turn preload after getting zero lash with adjustable rockers and pushrod set up 3/8x24 adjusters equal right at .0416 so I use .042 per turn, 7/16x20 equal .050 per turn I like to see between .012 to .025 clearance under the lifter retainer to the pushrod cups cold on iron heads and a little bit more with aluminum heads, say another .006 deeper, with the intake manifold off
if you have non adjustable rocker arms order a checking pushrod and use it to determine which length non adjustable pushrods you will need.
I would check at least two cylinders, one on each side, and both valves to see if your going to need different length pushrods on one side or not and also if the intake valves need a different length pushrod than the exhaust valves do.

I agree to a point. If you're close on valve to piston you certainly don't want to run more than you need. I prefer to run around .080 and set it up to where it's not on the edge of losing control.

Reason I say that is, if you run 1/4 turn, or .010, if the valves bounce on the seats (at all) the lifter plunger hammers it's retainer. (if you've ever seen the clips blown out of them).

There are many opinions on preload but keep in mind that the rocker ratio is 1.5: 1 so, for example, .025 preload is .0375 at the valve. With a pumped up lifter, the valve won't hit the seat. Now keep in mind that you are "preloading" a hydraulic lifter BUT if you were running a solid lifter of any sort you'd be adjusting "lash" which is a gap at the valve. So why does one get preload and the other gets lash ?!? Well we know "lash" ensures the valve hits the seat and closes. But what's the deal with preload ??