Lifter knock / pushrod problem ???

[Charger1968R/T]

I am new  in this forum, but I hope someone can help me with a headbanging problem.   
Engine spec :

440, 906 ported heads, TRW 12:1 pistons, hydraulic Comp cam nostalgia .509, stock rocker arms. HW oilpump, procomp 850DP. Ign. timing set to appx 38 before at appx 4500rpm.
Everything is new inside engine, the cam was a "complete" set from Comp Cams, timingchain lifters and pushrods.
Pushrod-length 9.315 diam 5/16".

Oil 20W/50W,

And a and short story :

- Cold start, or when the engine idles after cold start, I have idle appx 1100rpm, (the idle mixture 4 corner is not yet perfect, but it is running), it drops until appx 700 rpm when I put it in drive. Then I have no knock or noise.
- When engine hot, I have the same idle in park and 75psi oil pressure, when I put in drive, appx 700rpm, and oil press drops to appx 65psi, then I get a, what I assume, lifter knock. I think I can locate the noise from cyl 1, when I use stethoscope, the noise is clearest from the front left vallypan.
- When I switch to park, the knock disappears completely after about 0.5 sek.

No noise when I rew the engine. And I have not had the car on the road, just rewing in garage.

- Have also disassembled all the lifters, drained them for oil and put back in, checked the pushrods. But still the same when oilpressure drops.

Anyone have some ideas ?? Can it be the pushrods that is a bit to short ? I see comp cam has 9.315"(the ones I have) and also 9.400".

I appreciate all help I can get, Thanks !!

[justcruisin]

There is no way to be sure of those lifters, swap them out for a set of Johnson Hylift. There is a sticky post on them in this section.

[67RedCharger]

Make sure you have added the ZDDP suppliment to your oil before the push rods wear out your cam.

  ~ Don ~  67redcharger

[johnnyseville]

Contact the cam manufacturer, no one is as capable of diagosing these type of issues as they are.

[Charger1968R/T]

Thanks !

[Charger1968R/T]

A little update if someone has same problem.
I solved the knock/tapping noise With change the lifters to comp cam antipump up lifters. Still a bit noisy valvetrain cause the anti pump up lifters, (about zero to 1/8 turn preload, almost sounds like mech/solid lifters), but way better than before !!

[68CoronetRT]

A little update if someone has same problem.
I solved the knock/tapping noise With change the lifters to comp cam antipump up lifters. Still a bit noisy valvetrain cause the anti pump up lifters, (about zero to 1/8 turn preload, almost sounds like mech/solid lifters), but way better than before !!

Zero to 1/8th turn? From my gatherings you need at least .020-.060 preload which in a normal adjustable rocker arm would be 1/2 to 1 full turn(Each 1/4 turn is equal to .010). I bet they would quiet up with another half turn each.

Unless the anti pump up lifters have different specs for preload?

Edit: I missed the part about stock rocker arms. I think you need to check for pushrod length and get custom one's made in order to make them 100% quiet.

[Challenger340]

See here about this problem
http://www.dodgecharger.com/forum/index.php/topic,95605.msg1094731.html#msg1094731