I recently did some head work on my 20r. I had it surfaced, fixed some exhaust studs and did a new timing chain. I got it all back together and it runs fine at idle until it gets to about 2,500 to 3,000 rpm,s. Then I can hear a loud clanking noise coming from the valve terrain. I have adjusted the valves numerous times and the noise still persists. When I took the head off the truck ran fine. The noise doesnt sound like it is a rod knock, but more a loud tapping coming from the valve cover area. Could it be a lifter? Any help would be appreciated.

No lifters on a 20R.

Well it has an early model 22r block and a 20r head.

Wait...
you got a pre 84 22r block and a 20r head, did you gasket match the head to the 22r bore?

Yes, I dont think that is my problem because I have been running this setup for years without any problems.

quote:
I had it surfaced

I built a bunch of hybrids(22r block/20 r head)
If you dont clearance the head, the pistons will kiss it if the deck hight is low
The 20r chamber is way smaller then the 22r

I'll bet the pistons are touching the head.

I dont delieve so. I have checked the clearence and it appears to be adequate. Thanks for the insight. Does anyone else have any ideas,

I think Tazgi has it.. and I can understand you not wanting to believe it! lol.. you can probably use a stethoscope to find our for sure..

maybe you should describe the noise. is it rythmic and increase as rpm increases, or is it random?

if your worried about piston to valve contact, play-do it.