3.9l V8 TDC keeps changing

Hi, im in the process of fitting Megajolt on my Disco 3.9 serp. I need to find TDC and have no dizzy fitted (replacement engine). Everytime i turn the pulley 1 full cycle tdc seems to change on the pulley. Sometimes its seems as much as an inch difference.

Ive tried the steel rod in cyclinder 1 spark plug hole and rotated both ways..half the distance..that was wrong

Ive tried looking into cylinder 1 with a torch as i can see it rise and fall. This method the TDC on the pulley changes every 1 rotation of the pulley (upto an inch sometimes):wtf:

What am i doing wrong

Sounds like you are seeing the time the piston doesn't travel.

You need a timing disc and pointer, mark when piston first reaches TDC, starts to leave TDC and the centre of those 2 points is true TDC.

cheers for the reply. I tried that and it didnt give me a true reading for some reason.
Used digital verias in the end in piston one to get the true reading. Not just me that couldnt understand what was happening

Slack chain?

piston to conrod, conrod to crank, crank to pulley lol so cant of been