Re: 454 valve keeper fails, but valve not bent?
the GM method? the dealership flat-raters method that never heard of a performance cam? Probably the underlying problem. Likely that one was loose enough to let the rocker arm get cocked, it's all downhill from there.
Don't worry about hearing slight hissing from the crankcase, it's normal. Just a little ring leakage.
ever heard of the EO/IC method that gets it right the first time, every time? That works longer duration cams with long lash ramps? This has been discussed at length here hundreds of times. I personally have been hammering on this for 14 years.
Check ALL your pushrods by rolling them on a flat surface like a piece of glass. if more than a few are bent replace the set. Check ALL your guideplates by removing them from the engine and inspecting them closely, like with a magnifying glass in good light. if any are cracked or bent get new GM guideplates. Check all the rocker studs for signs of wear in the section where the rocker ball rides or bent. If more than a couple are worn, replace the set with ARP.
Check the tips of ALL the valves while you have ALL this stuff off.
Stop trying to minimize the problem and the amount of work involved in fixing it. Seems like this is your MO here. It's going to leave you doing the whole thing again. Sorry, don't mean to be harsh but this is the way it comes across. Bullet dodging is not a reliable engine building technique.
Here's the EO/IC deal. It's written as if adjusting the valves on an already built engine but you can get the idea pretty quick.
Back off all your rocker nuts at least two full turns. Turn the engine with balancer bolt or remote starter switch till #1 exhaust just starts to open. Judge this by eye, you can see it the pushrod move up. Turn the #1 intake nut down to zero lash, confirm by rattling the pushrod up and down and spinning untill the play goes out. This is not particularly critical given the range of adjustment allowed. Adjust the intake to 1/2 turn preload. Go to number 8, turn the engine 1/4 turn, see the #8 exhaust pushrod start to move up, adjust the #8 intake as on #1. Then turn the engine another 1/4 turn, see the #4 exhaust pushrod start to come up, adjust the #4 intake as before. Go thru the firing order 1-8-4-3-6-5-7-2. Back to #1, turn the engine till the #1 intake valve goes to full open and starts to close, it will take like a full turn of the engine. Adjust the #1 exhaust like all the others. Turn the engine 1/4 turn, see the #8 intake go to full open and start to close. Adjust the #8 exhaust as before. Give the engine 1/4 turn, see the #4 intake go full open and start to close. adjust the #4 exhaust as before. Go the rest of the way through the firing order as before. Sanity check: when done all the nuts should be about the same height, all the rocker nuts should be about the same amount of stud sticking out. If any are way off do that valve again. It may be that all the intakes are different than all the exhausts, either higher or lower.
Or, keep doing what you're doing now.
Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.