Hi all,last month I took the truck on vacation pulling about 4000 pounds with me out I-68. VERY HILLY. Anyway, It was pulling poorly and heating up some, but I thought it was just the hills. Well, two weeks before I modded the kegger, changed the plenum plate, and tuned up. Plug wire one was just touching the manifold at the back and burned through. So basically I was running on 7 cylinders for about 100 miles. It got like 240 hot and now has a tap. I changed the oil on the way cause it thinned out but the tapping didn't stop. It only does it when it's warmed up and cruising at little point in the accelerator where you don't have a real load on it, but you aren't idling either. It still runs stong since the mods, the new oil still looks good after 700 miles, not blowing any smoke. I did try retorquing all the rockers but that has had little effect. Thinking I may have weakened the lifters. Any other ideas before I go into teardown mode? 5.9 v8, auto BTW

 

if its running ok and its only the noise that's bothering you, i'd try a bottle of old fashioned stp. its some slippery stuff...

 

or... Try to actually diagnose the problem instead of covering it up.. lol
Pop the valve covers and take a look at everything in there. The majority of the time that's where those type of noises come from. Also, check all your heatshields and things like that. On one of my Rams, the heat shield on the pass side under the manifold was making a tapping noise just flapping around on itself. I yanked it up and the noise went away.

 

I actually did pull the covers and did check for loose items. Nada. The screwdriver stethoscope tells me it's under the covers, though. Since I retorqued the rockers and had minimal change, I started leaning towards the lifters aren't holding their lift like they should. I am thinking of throwing some engine restore or a little tranny fluid in oil to see if that takes it away. That will likely confirm or deny my theory if there is a change or fix of the tap.

 

Try Rislone engine treatment.

 

i tried the restore stuff.....did wonders for my oil PSI....went from 35-40psi idle to around 50-55 idle......that was aboutthe only differece i really noticed with it.

 

240 isn't that hot, and these engines are quite tough. I had a customer come in with a 99 1/2 ton (360) who continued down I-25 at 75-80 MPH for 9 miles after his water pump seized. It got so hot the air actually melted the plastic radiator tank, and the oil was beyond fried. My infrared put the head temp at nearly 500* F (don't remember exactly). He was low on funds, so we ended up just doing a water pump, radiator, hoses and changing the oil. It had fairly low compression after that (ring tension goes bye-bye at those temperatures), and was missing on a couple holes, but it was still running months later when I left that shop.

That said, the noise you're describing sounds more like wrist pin or piston slap than tappet or bottom end. Lifters are typically most noticeable at idle, and rod or main present loudest under load. But piston slap or loose wrist pins become most audible with some RPM and very light load.

Obviously, this is the best I can give you without actually hearing it, but unless you can't stand the noise, I'd say just drive it. It may get worse, it may not. I've heard old LA engines with nasty wirst pin noise make said racket for a long, long, loooooong time with no further issues.

 

Spun main bearing?

 

The OP already stated he pretty much confirmed the noise is coming from the top end. engine restorer is junk, and STP is not the way to go.(sorry DV). STP will cause more probs. In the old days,LOL I rebuilt plenty of motors with that crap in it and it's a nightmare. Try the Rislone or some MMO in the oil to replace a quart of oil. If it's just a sticky lifter either one might work, but, not magically as soon as you put either one in. Give it some time.

 

My 87 5th ave had a knock under the same conditions (at steady RPM no load on engine) and it was the timing chain slapping the timing cover. Use your stethoscope or screwdriver and see if the noise comes from there.