do you think that the 3 nm I discussed in my post would make much difference , as my son is a mechanic I might borrow he's , cheers.
No, it won't make that much difference. While the wrenches themselves can be very accurate, the over all process in not that accurate that +/- 3 ft/lbs will make any difference on 150 ft/lbs.
<edit: As your son has one (some?), why buy your own? I would think it's about time you got some payback!>
ARP prefer to use the stretch method of measuring rather than using a torque wrench due to the inaccuracies you mention. Not always possible though so the torque wrench it is for most things.
