I also have this posted in the 87-97 forum, but I think it may fit here better.
I have a 97 460 that has had a pinging issue. I have tried seafoam in the intake, retarding the advance, but nothing seem to take care of the problem. no engine codes at all. I did a compression test yesterday, (truck running smoothly) and found all cylinders were between 160 - 175 psi, except #3 which only had 125. So I know I have a problem there. I have since removed the intake manifold and am about to pull the head. The intake gasket all looks good, no visible leaks. There is a lot of wet gas/oil residue in the upper intake. Any thoughts on what is going on iside this motor? It currently has 77K on it. Thanks

 

Was the engine getting hotter than usual during operation? You could have a pre-ignition problem from carbon build-up on the piston causing the pinging.Also, on the #3 cylinder did the cylinder pressure leakdown fast or did it just stay at 125psi?

 

Superford, it sounds like your into this thing hip deep. When does it ping? Under load, part throttle, full throttle? My guess is it's a part throttle issue. If so, I would look at the EGR. They tend to clog and exhaust flow is reduced which will result in part throttle ping. Sure temperature, timing and fuel octane rating will affect the engines ability to burn fuel with out detonation, but most of the time those things don't change and are easy to rule out. Ping is detonation (an explosion), which is not how the engine was designed to burn fuel. Fuel is supposed to burn rapidly and evenly from the point of ignition (spark plug) to the quench area/cool (relatively) piston top/cylinder wall . If it explodes it will rattle the piston and rod/main bearings and that's what you hear. Carbon buildup on the piston can act as a source of pre-ignition/detonation. High octane fuel is actually designed to burn slower with less propensity to detonate at higher cylinder pressures. A lot of people are under the misconception that high octane fuel is more explosive when the opposite is actually true. A partially clogged injector can cause the cylinder to run lean and contribute to ping due to higher cylinder temperature; same goes for vacuum leaks. Since the heads are still on, you can do a backyard leak-down test. You will need to put each piston at TDC on the compression stroke (one at a time) and hook up an air compressor to the spark plug hole(a compression tester can be modded for this). Pressurize the cylinder and look for the source of any air leaks; leakage into the intake and or exhaust indicates a bad valve(s). Air leakage from the oil cap indicates worn rings. Oil in the intake may be normal byproduct of PCV. Fuellie motors don't have gasoline in the air stream like a carbed motor to wash down the intake runners. Good luck with your troubleshooting and let us know what you find.

 

Pre-ignition is totally different from Detonation Bern. Detonation is instantaneous, whereas Pre-ignition is a slower burn like the actual spark plug igniting the fuel. It just starts earlier in the cycle.But, there is Detonation from pre-ignition also. Just wanted to clear that up.I learned something from your post though on the part throttle ping!

 

It is a part throttle ping, under load. I was too worried about the low compression to let it sit and watch the pressure drop. I do know that it seemed to take a bit longer to get up to the 125 psi than the other cylinders. I am close to having the head off. it is all unbolted, I just need to remove the lifting bracket and lift the head off. I will let you know. Thanks for your help.

 

Well I finally got the head off. Everything looks good. there is a bit of sludge and carbon, but not on the pistons or valves. The gasket had no obvious damage either. I think I will get the head cleaned up and reinstall it with a new gasket. I'll see what that gets me. Any other ideas?

 

Upon further cleaning, I can now see that my head is cracked! It is cracked at the #1 exhaust port, where the bolt threads in to the head. Is this fixable, or do I need a new head? What are the chances of other cracks?

 

If it's a crack in a bolt boss, you might be able to braze it and install a heli-coil? Ask your machine shop...