Push rods and hydraulic lifters

[1970FordTK]

This engine is a rebuilt 360, to stock 360 specs. Its still running a 2v intake and carb. Other than the valve train noise this motor runs like a champ and is doing well.
Due to finally getting a dial caliper that could measure 10". I have found out why my valve train is chattering so much and why I have over .030 gap when the valve is closed to the bottom of the rocker on 6 of the 16 valves. The pushrods that where put in by the PO during the rebuild where 9.55 by the caliper, I can only figure that these are the 9.56 listed ones that are supose to be -.030 short. Only having run about 1200 miles on the new rods and lifters, I have several questions I'd like opinions and info on. I've ordered new pushrods, first question is will I have to pull all the lifters to drain part of the oil out of them before running the new rods?
Next, being that part of the valve train is worn so that its at a measured .030 between the rocker and the valve would it be wise to run the .030 over rods (9.62) on all the valves or just the 6 that where that far out?
How much variable give (range) do the hydraulic lifters have?
All opinions and info will be greatly appreciated, thanks in advance.

[MotorDog]

Assuming all Push Rods were the same length, I would take a look at the cam lobes for the possibility of some excessive wear there. They shouldn't have opened up to .030 in just 1200 miles. Either the cam or the lifters are flattened out to provide this amount of clearance. If the cam is flat, then new Push Rods will only last until the cam or lifters flatten more and you will be back to the same problem. I would definitely look further for the cause of the problem.

[1970FordTK]

Like I said before, PO put -.030 rods (9.56) [new rods] in during a rebuild. He died, not having the hydraulic lifters pumped up to check for valve train to see if it was within tolerances. Had to drive it a bit to find out for sure. After having to finish debugging the engine for lots of other things (electiral crap). Also, not use to not having adjustable rockers, and having to eliminate other things I finally got around to working on this part. Its not the cam lobs, but you can be sure that the rockers have a lot of wear on them. Only truly part that wasn't replaced or rebuilt was the rockers.

[My427stang]

If all 16 are too short, you just need to swap them for the correct length.

When you tighten the 4 rocker arm bolts though, go slow, otherwise you could bend a pushrod. Using your ratchet, just work across all 4 until they are tight. The oil will push right out slowly

[Dragon]

Fe hydraulic lifters are adjusted by the pushrod length and the PO did not do his job right. Always start with standards and make sure they do not sink the center of the lifter more than .015 or have free clearance. On most hydraulic motors I have built they always used standard length.

[1970FordTK]

Thanks guys.

[Hawkrod]

As to your question about pushrod length based on your measured clearance, it is important to remember that the rocker arm has a ratio and that clearance at the valve tip measured .030 so clearance at the pushrod ball in the rocker cup will actually only be just over .017 due to rocker ratio. Hawkrod