I'm pretty certain I know the answer but want opinions in case I missed something.

This is a 390 in my 68 F100 that was parked in 1984-85 because dad said the engine had a "tick". Another family member got hold of it a few years back, got it running again then did nothing more with it other than start taking the top end of the motor apart. I got it back a few weeks ago so I went ahead and replaced the cam/lifters and did find a couple bad lobes on the cam and dished out lifters.

Got everything back together yesterday and fired it up. Everything cam and up is either new or has been checked out, valve springs are all good, lifters are pumped up, rockers are good. There are some exhaust leaks but the sound I'm hearing is neither and exhaust leak tick or lifter tick. It lessens under acceleration and is much louder on deceleration. I'm no mechanic but from my limited experience I think I have a rod that is preparing to leave the party.

 

Perhaps a dumb question but, did you properly break in the cam? Drain oil, check for metal flakes. make sure rods are spinning etc? If you didn't you could be right back where you started.
Does sound like a valve to me. Briefly run it with the valve cover off. Should be able to tell a lot.

 

All I heard was lifter tick.

 

Yes and yes, I did properly break in the cam, varying throttle from 2000-3000 rpm for 20+ minutes. As for verifying the push rods are turning, I marked all of them when I inserted them and have not pulled the valve covers back off the motor. Same with oil, I have not dropped the break-in oil to check it either.

Unfortunately taking video from cell phone does not sound the same as in person, the tick is far more solid in person and listening from different places puts the noise a lot lower in the block. I should have taken the video from under the engine, it seems more pronounced from below the motor.

 

Could try an automotive stethoscope. It muffles engine noise and helps you pinpoint sounds.

Connecting rod knocks can sound like someone hammering on your block. Any idea what your oil pressure is? Low or zero oil pressure might mean a spun bearing.

 

That "louder" on decel means something. Like crankshaft thrust bearings. Does it have a clutch? At the high point of this "knock" press on the clutch hard enough to get some resistance, but not enough to disengage it. See if it changes (worse, better, goes away).

The metal going through the oil from a wiped cam lobe or two is enough to ruin everything. Had the same thing happen. Metal everywhere, and at only 1000 miles (and a bunch of oil changes for break in) the main and rod bearings looked like they had been running in sand. And yes, the thrust bearings looked like they were pretty much gone, so much so that the crankshaft was unusable. It could have been welded up, but wasn't worth it.

Hate to be a downer, but ... sounds like it's time to take the bottom end apart.

 

It just has the original gauge on the dash, not just an idiot light. It does show oil pressure come up from startup to the upper end of the "normal" range, then drops back to the middle once it warmed up. As for the stethoscope, went to get mine and listen to it and like much of my tool collection, it seems to have been "borrowed" with no return in mind.

No clutch, it's an automatic. Had a few different people through the shop today with varying degrees of mechanical aptitude ranging from the old farm hand that can make anything run to the ASC certified "technician" and all 4 had different "opinions" of what might be wrong. It's a bad lifter, bent push-rod, bad valve and finally a bad rod bearing. All agreed that I need to let it idle and pull one plug wire at a time to see if it goes away or gets quieter on one hole. All agree that the sound is more pronounced on the right side of the engine so I'm half way to finding out what it may be. My long handled, insulated plug boot tool has gone to hang out with the aforementioned stethoscope so after getting a heart-reboot on the first one, that got put on hold till the brown truck arrives with more tools.

In the end, I think this truck goes back to the end of the warehouse with the rest of the "projects" and once the 74 is back together and out of the way, this one is the next to get the engine on the stand. I see more $$$$$'s slipping away.

Or maybe when the weather cools down a little and the cruisers start rolling down the road I'll shove the whole lot out to the curb with For Sale signs on them.

 

There's a signature quote in there somewhere

"Someone took my plug boot tool, and all I have to show for it is this new pacemaker."

 

BTW, thinking about it more, wrist pins like to do all sorts of weird noises.

That louder on decel is not rod knock, I don't think, unless the thing is really egged at this point.

 

Still haven't gone beyond pulling one plug but I think we may have found an issue if not the issue. The old farmer type that hangs around my place wanted me to pull the right valve cover off and fire it up. I did and happy to report even at low idle the push-rods are all turning well. However this has shown a potential bigger issue, after running for a few minutes (2-3), there was very little oil collecting in the head. So the 52 year old pressure gauge on the dash does rise, does indicate "some" level of oil flow and pressure, it is appears to my untrained eye that there is no where near the amount of oil making it's way up there as should be.

I have an oil pressure testing gauge coming tomorrow, going to see what it says is really happening with the pump and go from there. I have my fingers crossed that it is in fact the pump and in turn not keeping the lifters pumped up. I know a new pump is only a band-aid to what will likely be a much larger problem depending on how long this was driven with the pump not providing full flow. But it may buy the time till I get one out of the way to pull this one in for more in depth motor work.

 

Plug boot tool ? You mean he's missing a rubber glove ?

 

Pull the rocker shaft bolts and see if the turned down bolt is in the hole where the oil feeds from the block. Three are full size shanks, one has a smaller shank that the oil from the block flows around to get up to the shaft.

 

Did that on both sides, also cranked it with that bolt out to check for oil flow, there is plenty, almost shot it over the fender. Plugged in the test gauge, 40-50 psi oil pressure. Tried pulling one plug at a time to see if the sound changed and nothing, no notable changes so I have given up on this motor for now and shoved the truck back to the back of the warehouse. I already have one torn down that started out a perfect running 360 with a minor oil drip from the rear main that has turned into a giant money sucking project, I'm not too enthused about opening an other FE money pit.

 

I got bitten once by an MSD 6AL ... ain't never ever going near that thing again. And that's coming from someone who as a kid once got zapped by an oscilloscope flyback transformer direct from one hand to the other and woke up on the floor. Nope...

 

Duraspark will do it too Seen one throw a spark across a 400 once.