collapsed lifter? loose rocker arm? wiped out cam lobe?

[dbmx66]

so its been bothering me lately, i have a 84 k10 with a 350, real real mild cam. hydraulic flat tappet, somtimes when i fire it up, it makes a weird noise, its definitely in the valve train, but it doesnt make the noise all the time though, itll only do it every other day or so. i didnt get around to pull the valve covers off yet, but i was told its either loose rocker arm, collapsed lifter, or a cam lobe got wiped out, how do i trouble shoot this, i wasnt really trying to pull the intake and everything off right away. and one cylinder during the cycle seems to misfire, but not every time, so im confused on what to do. any help would be appreciated. thanks

[Cue-Ball]

Should be pretty easy to verify a loose rocker without taking off the intake. But to check for flat lobes, you have to remove it.

First, pull the valve cover and check for a loose rocker arm by hand. You might have to turn the engine over once or twice because at least a couple of rockers will always be under tension. If you've got a loose rocker don't just tighten it back down. Sometimes the lock nuts loosen, but often a loose rocker is caused by a flat cam lobe or collapsed lifter.

Collapsed lifters can usually be seen by eye. With the lifter/rocker on the base of the cam lobe (not under tension), the "eyelet" of the lifter should be up at the top. If it's sitting down inside the lifter or if you can easily push it down by pushing on the back of the rocker, you've got a bad lifter.

To check for a flat cam lobe you need to use a dial indicator with a magnetic base. You should be able to find one relatively inexpensively. Set the dial indicator on the top edge of the lifter and have someone turn the engine over (or turn it over by hand). All of the intake lifters and all of the exhaust lifters should move the indicator by the same amount. If any lifter comes up short, you've got a flat lobe.

Also do a visual check for broken valve springs or springs that have slipped off their seat.

[slinginrods]

Attach a vacuum gauge,it should read around 18-20 inches of vacuum and be steady.if it bounces up and down you have a valve train issue.to check if it's intake or exhaust.screw a compression gauge into the bad cylinder(s).then hook compressed air.a steady strong stream thru the carb indicates intake valve or related.thru the exhaust then it's an exhaust valve or related.make sure yo do a compression test on all cylinders first to see if any are low.if a cam lobe is gone the engine will pop throughout the carb as you rev the engine in park.sort of like a popcorn machine.
Posted via Mobile Device

[MalibuSSwagon]

You could start by setting the valve lash per factory procedure. Easy enough to do and takes maybe a half hour taking your time.