304 engine noise under load
I have a '74 Scout with a 304 in it. I built it about 5 years ago. Runs well. Started hearing a tapping in 3rd and 4th gear as I accelerate. Does not sound like a knock but a tap, especially when I'm cruising and then give it just a little more gas. Don't think it's spark knock. Checked and adjusted dwell a few degrees. Tried premium gas, tho I really had to bite the bullet on that one. No help. Checked the lifters for play and used a stethescope to listen for any errant noise at idle. Nothing. Only seems to tap under a load. Good compression, so I don't think it's valve train related. I'm going to try to clamp my stethescope with a long hose on it to various engine parts and listen for noise when underway and under load. Any ideas?