79 Series 1hz Knock Ideas

[79SeriesWA]

Hi everyone, grab a beer, long story ahead.

Recently picked up a 2000 79 series 1hz with 280000k's on the clock. Has a dull knocking sound at idle and increases with rev's then seems to disappear just over 2000rpm. It's not louder under load etc. When i do the old screwdriver to the ear trick on the injectors the front 4 are making a nice ticking noise with no other sound, however the back 2 have got a knock to them, especially the back injector(can't hear a tick just a knock!)
I have fitted an oil pressure gauge and its smack bang within range as per the book, I was thinking it might be the main bearings, are these know to have problems? But wouldn't the oil pressure be low if the mains were on the way out? Would i be able to hear the mains like I am through the injectors? Or could it be the big ends? Now im thinking it might be injectors, service history is unknown so I guess it can't hurt to chuck on a new set of injectors It's doing my head in!
Thanks for reading the short story, hopefully someone out there can help me!
Cheers guys.

 

[ForealBoreal]

Ah check your injection timing, do your valves and a new set of injectors wouldn't hurt it.

 

[Aussie 25]

Ah check your injection timing, do your valves and a new set of injectors wouldn't hurt it.

X2 and then think about pulling the sump to look at the bearings.

 

[79SeriesWA]

Thanks for the replies. Picked up a new set of injectors today will chuck them on tomorrow and do the timing and valves at the same time. Hopefully this solves it.

 

[yotahed]

I had a diesel knock volume increase when i put new injectors in. noticed it right away. thought maybe i didnt seat something correctly... 5000kms later and still there... runs fine.

 

[fat wagon]

I had one injector on my 12ht that had a knock turned out to be the fuel suppy line wasnt tight, also the clamps that attach the supply lines to the engine can cause injector knock