let me try and explain this better .
on this job i am moving the fire wall back 10.25" in the car this is so i can move the motor back the same and the driver back also the same amount in the car .
i had to get the fire wall around the roll cage tubing i welded in before i moved the fire wall back
as you can see i welded in the roll cage tubing before i started to fill in the fire wall filling it in around the tubing .
the car owner wants to see the welds so he doesn't want me grinding and dressing them in at all . but i did around the tubing . i had a U shape cut to fit the fire wall up around the tubing . when i was done i dressed in the weld by grinding them smooth so you couldn't see any of the welded seams .
this is how i also do the welds when i do flares on cars also with patch work and when ever i do butt welds .
you see this TR chassis the patch work i did i also did in the same way i but welded in the patches and dressed in the welds so you really can't see them making it look as all one piece .
by doing this and making all one piece again you do not have the heads if the welds sticking up . it's all the nooks and crannies that if you just spread filler over will end up rusting out later on . if it's all one nice seamless piece you 1st will not need as much filler or any filler at all and then being one piece there is no seam to worry about blowing out later on .
rust around weld start from a few reasons one is what i just said about the nooks and crannies the other is from small pin holes left were you did your welds . moisture will find it's way thru the pin holes over time and blow out your welded seams .
depanding on the job and what the customer is looking to get and pay for depends on how i dress in the back sides of the panels too . with some lower costing jobs i will only seam seal the back side of the seams to hold out any moisture with the high quality high paying jobs i will also dress in the welded seams on the back sides of the panels . by dressing in the back sides you again get one seamless welded piece and with that you will not get rust around the welds as there are none left to see or feel . it's just all one piece when finished so you just spray your E type primer and then your filler primer and it's good to go from there .