CrustyJunker
Is STILL Here?
I don't think spark plug gap would make it run THAT bad. It's not impossible, but I wouldn't think it's likely. I also have my plugs gapped at .040 and I have never had a problem in the 13 years, three sets I've put in, or 170,000 miles I've put on having them set up like that.
Lifters on these are always noisy on cold start...Typical small block Chevy. As long as you got oil in it and it quiets down within several seconds, it's no big deal.
Once I had a poor quality aftermarket fuel pump that was weak but didn't completely fail. It wasn't putting out the volume to keep up and wouldn't go over 3,000 RPM under load but would be able to hit 5,000 all day in neutral. Showed fairly okay fuel pressure at idle and revving it unloaded (~50 PSI). It didn't show any check engine lights or anything until one time cruise control made it go lean and misfire for too long. Then I got low voltage O2 codes. That could be something to consider. BUT...
What's got me thinking is your poor idle. That almost sounds ignition/timing related. When I had a bad distributor gear (that rides on the back of the cam), I had a check engine light on it -cam/crankshaft correlation fault. This caused poor and rough idle, and low RPM cruising it chugged and sputtered with an occasional backfire. How many kilometers do you have on your truck, and has that gear ever been changed?
Lifters on these are always noisy on cold start...Typical small block Chevy. As long as you got oil in it and it quiets down within several seconds, it's no big deal.
Once I had a poor quality aftermarket fuel pump that was weak but didn't completely fail. It wasn't putting out the volume to keep up and wouldn't go over 3,000 RPM under load but would be able to hit 5,000 all day in neutral. Showed fairly okay fuel pressure at idle and revving it unloaded (~50 PSI). It didn't show any check engine lights or anything until one time cruise control made it go lean and misfire for too long. Then I got low voltage O2 codes. That could be something to consider. BUT...
What's got me thinking is your poor idle. That almost sounds ignition/timing related. When I had a bad distributor gear (that rides on the back of the cam), I had a check engine light on it -cam/crankshaft correlation fault. This caused poor and rough idle, and low RPM cruising it chugged and sputtered with an occasional backfire. How many kilometers do you have on your truck, and has that gear ever been changed?