Okay let me start of by saying I have a 383 with Morel lifters, LE3 heads, CC 26120 springs, and 7/16 Pro Magnums with GM guide plates, and Trickflow hardened pushrods. I've been having alot of problems with valve taps since I got the car together. Everything is brand new, I started off by setting the valve lash at a half a turn, which is where I was told the Morels run the best. That was way too tight, and the starter was spinning the motor freely. So I then did them an 1/8 of a turn which is the most I can turn them with out loosing compression. I start the car up and it runs good, then it gets hot and it starts tapping again. So I take it apart and some of the rockers are loose. Heres the wierd thing, I can tell which ones are going to be loose, by looking at the set screw in the polylock. When I adjust them there is no up and down movement in them though. I've tried every different way to adjust them trying to make sure the valve is shut all the way, and still no luck. I chech the length of every push rod and check to see if they're bent and they're all okay. I checked every rocker arm, and they all seem okay, and there is oil coming up through the hole in the rocker arm when I'm adjusting the them, and the oil pressure is good in the motor( its brand new, with a new Melling high pressure pump.) Do you think my issue is in the lifters? They don't feel spongey, and they are pumping oil up threw the push rods. What could cause this?

 

Adjust them hot.while it is running.

 

I have a valve cover mounted delteq and over the valve cover wires, so running it with the valve covers off isn't really an option. I noticed that if I open the one intake valve and put a dial indicator on the rocker, its slowly shutting while the cam isn't moving. This only happens on one cylinder, I really think its a bad lifter, but the only thing is that its actually sitting too high, almost like its getting stuck in the lifter bore and slowly seeping down. As I stated before the machine work is all fresh, theres plenty of oil pressure, and all the lifters slid in easy. I'm lost. I guess tomarrow I'll pull the intake and take the lifters out and go from there.

 

If the problem is your lifters, that will be the first failed Morel I saw.

BTW I also adjusted my valves 1/2 preload after zero lash. Try 1/3 or 1/4 preload.

 

Try less preload. I was only running 1 flat on my Comp lifters.