Roughly for how long should i do this?
Been almost 2 weeks now
Heloo (I'm back off my holiday now!) Running in older engines is often debated as people have different opinions on what is the right and wrong thing to do. Generally speaking newer engines don't need extensive running in periods, if any, because they're built to such precision that the amount of wear needed to make the pistons "fit" is barely worth troubling yourself about. Older engines like the 2.5 N/A are old hat in terms of engine build technology and therefore required that little bit of extra input from the driver.
When I rebuilt my N/A, I was advised (by my local landy specialist) to run the engine in to a fairly set regime:-
1) Coat the bores with cheap mineral oil before total re-assembly
2) Fire up the engine and alternate the revs from high to low continuously over a period of ten minutes or so, then switch off.
3) Apply a large load to your landy (ie. a laden trailer / load space or bricks)
4) Drive a trip of about 100 miles or so steadily and work the engine in higher gears (ie. lower revs but more strain)
Other people will tell you to be very soft on the engine. In my opinion there can't be anything wrong with giving it some work, it'll help wear the engine in that bit quicker.
From a scientific point of view (in terms of engine wear) I can only assume that running in time is the arguable factor. Either way, the engine is running, the harder it's worked, the quicker it wears in.
-Pos