I asked a few days ago about gig welding on car someone replied saying it mattered where you put the grounding clamp can someone explain where it should go and How close to the work. Thanks

as close to the work area as possible. Birdtracker

and on the same piece of metal.

i.e. do not put your ground clamp on an engine block or rear housing and weld on a chassis.

What they said..

whatever you do, do NOT strike the arc on the ground clamp to get started............
WHY some people do that is beyond my imagination ! i have been to many shops, and when i see ground clamps with weld boogers on them i get the creeps !

If you're striking an arc, you're either using a stick welder - definitely not recommended for anything close to a race car part - or you're using a stick machine with a TIG torch. Doable, but you lose being able to control the heat. If you must, use a copper pad next to where you are welding to avoid contaminating the tungsten.

I've also seen guys use the ground clamp to knock the wire back on a MIG if it got run out of the gun too far. Makes a s***mess of the clamp. For those too lazy to keep a pair of dykes handy.