@Dtdub34 i think someone mentioned a stethoscope already but I will reiterate, a mechanics stethoscope or automotive stethoscope can be of help right now. They start at $8 on Amazon and the one I have found useful is the long ended attachment. "There is no through hole", the ear pieces block out engine noise and by gently touching suspected parts or areas it can help locate sometimes. Worth the low cost.
I'll keep the majority of my focus on the valve train since you have scoured over your truck, but dble check the injectors and for exhaust leaks. I'd get a good light and put eyes all over your exhaust looking for that tell-tale sign of black deposits at a leaky location.
I recently pulled my heads and lifters for a cam swap and headwork, (90k mi, developed a serious tick while driving which faded immediately, but this was on the table anyway, so..)
Have you run your engine with valve covers off and checked for any indication of the tick? Tick will be louder. With engine running place your finger (with glove on) or stethoscope carefully on each rocker arm? Be super careful obviously, don't get sucked into the fan. You should feel the tick when you land on that rocker.
Could be a pushrod like you mentioned above, not only bent but worn. Out of 16 rods I found the end of only one worn. 15 looked damn near brand new but one was worn. See pushrod pic. Obviously won't see that but you'd feel it if it were the tic, bent is definitely an option also.
When you pulled your rocker rail did you do it with a "retorque method" in a pattern or just pull the bolts all the way out, one by one? I understand by pulling all the way out one at a time there is a good chance to bend that rail. Or by installing the bolts the same way, either could and probably would result in bent rail/a bent rod.
If you get to pulling the rocker rail take the opportunity to make sure the center hole on every pushrod is clear for oil flow. This is actually the path from which the lifters receive most of their lubrication. Partially plugged or plugged may result in tick.
The push rods are reused, correct? I hate to suggest throwing more money at parts without a positive i.d. but if I were going to do that this is where I'd do it. New push rods to go with that new cam and new lifters.
Lifters - obviously this would suck to have to go this deep but ya can't stop the hunt now; reason you really wanna make sure he tick is not somewhere else.
Once this deep pull em, every one and check for hydraulic pressure being retained by the lifter. If any aren't hard as rock I personally would replace. They may not necessarily be bad but its not holding pressure I don't want be back under the heads tomorrow or hearing a tick so I'm changing em. You might very well find a couple mds lifters that have bleed off. Im not an mds expert but am strongly opinionated thats mds is snake oil and I'm going mds delete every chance I get. Will need a tuner to modify engine controls but replacing 8 mds lifters. Which really sucks because now your under both heads not just the ticky one. But MDS is a call you make, not me. If you have flat mds lifter (s) find a specialist and ask how you can be assured that little pos is pumping up when the engines running, because you gotta tick and a culprit.
Oh almost forgot, with lifters out, check the side oil port on the lifter, mds only, on mine. But each mds has a port positioned in the hole on the side of lifter mine are almost all rotated out of position in the hole, see pic. I dont know exactly but I'm pretty sure thats how MDS is turning selected cylinders 'off' using the port to manipulate hydraulic pressure in the lifter. Im pretty sure also that little port needs to be lined up properly for it all to work correctly.
I'm gonna throw mine out. I had 15 lifters hard as a rock, again 6 weeks of shut off 4 weeks of being drained, 15 held hydraulic pressure, 2 were soft (mds) and 1 sponge (mds), all my roller and roller bearings look and feel very fast, and very round.
Thats whole lotta noise from me, and if you're not burned out on it yet, outstanding and good luck.
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