Replaced my timing chains on '98 F150 4x4 4.6L.
Turned it over and won't start. Pulled No. 1 plug and electrode is bent over and broken.

The new chains were one link off of timing mark, so I turned the cams one link to match. That is the only thing I turned and I wouldn't think that would be enough to completely thrash the timing.

What is hitting my plugs? Bent valves?

 

It would be a valve head that hit a piston crown for the bending.
No other relationship would change unless something lodged in the cylinder.
At one point in the cycle the valve could be within .100" from the piston head so a tooth off can make that .100 " disappear in a hurry.
Sorry, on these engines you have to be absolutely sure your timing is set correctly.
It's sort of like a carpenter, measure twice and cut once or you start all over again with a new piece/parts and labor/expense if the cut is to short.
There is no room for guessing.
Even in a push rod motor this can happen if the valves open at the wrong time, to max lift..
Good luck.

 

Thanks Bluegrass.

Now that I know what happened inside the cylinder, What would cause the camshaft sprockets to be one tooth off in the first place?

The old chains were extremely loose and were slapping against the block. The guides and tensioners were completely worn out. I assumed that the old chains had slipped over a link... You you what they say about "assume."

 

Get access to an OEM manual and page 303-01b-63, bottom page will show you the proper timing position. #1 piston (passenger side) all the way forward, should be at TDC, and the COPPER links should align as shown. On thing, the book states to align the DOT on the crankshaft fwd gear, I don't have a dot on my fwd gear....it's a recessed rectangle.
I just opened my engine up for rebuild and my chain guides and tensioners look really good, not much wear at all, which is impressive at 386k miles. I will be replacing these with new ones.
Pays to change your oil often and not just by the miles.

 

I can back up the oil change interval value.
My 02 4.6 is heading for 219,000 miles and is still near perfect running with no noises cold or hot and power as new.
Oil pressure is still over 50 psi hot running, 25 at hot idle on aux oil pressure gauge over nearly all the mileage.
Oil change interval has been 5 to 7k miles with filter each time using only MC 5w20 Blend and Quaker State DFY 5w20 blend with claim of added Zinc for reduced wear.
I began looking for a different oil several years ago as MC was so cheap but finally rose in price where DFY was now cheaper and fit the application for weight and blend. Have not detected any obvious performance difference between these oils and always use the MC 820S filter, each change.
Good luck.

 

The only oil I used was castrol 5w20 and basically any oil filter I could find, the cheapest. Last filter was fram, before that a BLACK one.......386000 miles, not bad huh?
I never changed my oil based on mileage, but visual and smell. Seemed to work for me.