valves vs lift pump?
 

so i thought my lp was going bad, but now i'm kind of worried that it may actually be a valve or some part of the valve train. this noise (rapid, high pitch tapping) does not happen unless i am actually driving. i've tried to locate it by running the engine up to 2k rpms or so, which is where it hapens when driving, but it doesn't happen when sitting still. anyone have any suggestions for figuring out what the heck this noise is? the only other symptom is a slight loss of power, very similar to the last time i had a LP go bad, but that's about it. ?????
oh yeah, it's not my overflow valve, just put in a new one

with windows up it can be heard the best somewhere around 1800 or 1900 rpm? Can only be heard while driving at these rpm's never at idle or just reving the engine up to these rpm's? Sounds like it directly in front of you?

it's quite loud. can be heard with windows up and occurs primarily from just below 2k to just above 2k, then it will usually, but not always stop around 2250rpms and then happens intermittently above that. i usually shift around right around 2500. yes, can only be heard while driving, never at idle, in fact never below almost 2k rpms, and does not happen while just reving. directly in front and maybe more on the drivers side, which is why i was originally thinking lift pump, but hard to tell for sure. pease don't say it's my inj. pump :(

My return line has a nasty tick to it, but thats mostly at idle. Have you run the valves with a feeler gauge lately? .10 intake .20 exhaust.

Jim

Since it wont cost you anything to try,(strange as it sounds) put a wrench on your exhaust manifold bolts (ussually 5/6) and see if they are all tight. The symptoms you describe sound like a similar problem a few people I know (including myself) have had. An exhaust manifold leak on these things can sound like a mechanical tick and only be heard at certian rpms with load.

My ticky was the overflow valve
 

I was able to diagnose the problem with a fuel pressure guage.
The noise was alot louder when the fuel filter was dirty.

SFB