Here is the thing with our lifters that seems to be the tale around here. It may have been misunderstood by me or mis-stated by others but, nonetheless, this is how our lifters work:
The lifter does NOT pump up to the retainer during operation. It will only pump up to contact the pushrod and put a certain (relatively small) amount of force on it. You can calculate that force based on the oil pressure at the lifter and the cross-section area of the lifter plunger. But think of it the opposite way. . . if your valve seat pressure is 100lb, it takes 100lbs to lift the valve from its seat. Multiply that by the rocker ratio (say 1.7) = 170lbs of force required to lift the valve from it's seat via the pushrod. Take that 170lbs and divide by the area of the lifter plunger (~.31 in^2) and you get 554 PSI of oil pressure required to pump the lifter past zero lash, it would take even more to lift it past that point. So if you are checking pushrod length via the solid lifter, make sure you account for a healthy preload with this in mind! Now lets talk about the preload . . .
The preload is there to take advantage of the hydraulic system. As your valvetrain wears out, the lifter will always have a nice zero lash since the lifter can pump up as required. If the pushrod shortens over time by .005", the lifter preload will decrease by .005". This keeps us from having to re-adjust the valve train every so often and it keeps the system quiet. With that said, you want .020-.060 preload as most will tell you. I opt. for the lower of the range, maybe .020-.030" preload.
Once you get the geometry at the valve tip checked out, there are plenty of ways to check the length of the pushrod you already have. I have a trick to doing it accurately on pedestal rockers with bled down lifters. You can easily find your required pushrod by adjusting the checking rod to a firm zero lash and adding .030" to the final length. I would do this with a hacked 'solid' lifter as stated above. Just put washers in it instead of the spring. I had to buy like 3 little bags of small washers at Home Depot to get the perfect combination of thicknesses to get the lifter seat to abut the retainer clip.
So basicly, if you just say 'adjust to zero lash with a solid lifter', you will end up with a shorter pushrod than what you should be using. You'll end up with zero preload which is bad for everything.
On the subject of valve float . . . The disadvantage of the hydraulic roller lifters is that when you go with a pointy-lobe cam, old worn out springs or just rev way to high, the lifter can pump up too much becuase it will float. This happens when the spring can't keep up with the cam. As the lifter rolls off the backside of the lobe, the cam will fall faster than the spring can move and the lifter is left hanging. Every time that roller doesn't touch the cam, the oil pressure pumps it up alittle more and after some more revving, it can in theory pump up to the retainer and it won't bleed down right away. Then before you know it, you have busted valves flying around the cylinders.
. Check out summit they are preaty close in price and after gas it may be cheaper to just order it.
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