I usually isolate the batteries with the cut off switch and unplug the MSD, Racepak and Dig Dash stuff. I've welded on the car more than once when I've forgotten to unplug things and never had an issue. Does it matter ? or have I dodged a bullet ? Like Cab and Rick says, I'd rather play safe and disconnect and / or remove stuff like SD cards
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'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03