John Deere 410 injection pump timing? / engine knocking (...

[Farmall M Beginner]

I have a '75 JD 410 backhoe with 5750hrs.
It was running great, been using it 5 to
six hours a day cleaning up my property
with no problems.
I was moving dirt with the loader for a
small building pad when I noticed a loss
in power and a knocking sound. I could
hardly raise the loader cause it would
kill the engine. After a little research I
thought I'd start easy and replaced the
fuel filter, air filter and primed the
fuel filter with sea foam. It did not make
a difference so I pulled the injectors and
they were terribly nasty so I put new
injectors in along with new "T's" on the
injector returns cause the old ones were
stripped out, egg shaped and were starting
to leak. The engine started much easier
with lots of power (can raise the loader
at a idle) but the knocking is still
there. I borrowed a mechanics stethoscope
and the knocking is definitely on the top
end. According to my book it has all the
symptoms of a out of time injection pump,
cause the engine is now hard starting, it
knocks and puts out black/grey smoke.
I checked the timing adjustment screw on
the injector pump and the locking nut was
about finger tight, I held the adjust
still with a hex wrench and tightened the
nut. The engine started up rough like it
has been and then was knocking like it was
before. Then the knocking started getting
louder and I quickly shut it off. I'm not
sure if I want to start it again, anyone
have any advice for adjusting the timing
screw on the injection pump?

Thanks for any advice!

 

[AJ.]

Knocking is always bad news, the first thing I would do is remove the engine oil filter and inspect it closely for signs of metal in the form of little flakes,if you find metal flakes it would be a sign that a bearing has picked up and that is the cause of the knocking you hear,the other reason for a knock is broken piston rings,when a piston ring breaks part of it will find it's way to the top of the piston,each time the piston comes up the clearance is so small that the ring will come in bedded in the piston and hit the head,check the blow by at the oil filler.
AJ