Chevy Roller Lifter Question

The engine I built for my T has a 99 Vortec block with roller cam. I reused the stock hydraulic roller lifters on a GM Ramjet 350 roller cam. This is my first roller cam engine.

After starting it for the first time it ran OK, but not really good. Had an irregular miss and an occansional sharp pop in the exhaust. Tuning (timing and mixture) made it a little better, but didn't completely clear up the miss. This miss occured at any RPM, not just idle. While tuning it today, it went completely sour and got to the point where it will hardly run.

I decided to readjust the valves just in case I screwed it up the first time. I noticed the lifters are bleeding down really fast. You can turn the engine over and watch the lifters bleed down literally in seconds. A valve that is fully open will bleed down until it is nearly closed.

I've read that these lifters do bleed down faster than older flat tappets, but this seems way too fast. This can't be normal. I'm thinking I need new lifters. I think the lifters are leaking down while running and causing the irregular miss.

Is this fast bleed down normal for these lifters?

OK, let's see if we can figure this out. Let's say the motor idles at 750 rpm's. That would be 12.5 revolutions per second. Any one cylinder in the motor will fire every other revolution, so that would mean that any one cylinder will fire 6.25 times per second at idle. So, if the lifters are not bleeding down in 1/6 second, there's probably not much to worry about.