A few opinions.
The Magnafuels 500 pump comes with decent sized gage wire to carry the increased amperage loads, if they are melted you might have a short somewhere. Are you using relays, or is the pump wired directly to the rocker switch? Trash isn't good for any brand pump & can lock them up. Even when a filter is used some trash can find it's way inside the pump. Freshly assembled steel braided lines & fittings need to be washed out before being used (grit from the chop saw wheel really builds up inside when cutting the line). Especially true for the pump-to-regs-to-carb(s) lines because when you turn off the pump fuel back-wash can pull dirt/trash trapped in the line back down the line inside the pump (especially front mounted cells/pumps).
While the 500 pump might be thought of as "constant use" rated, dead heading any brand pump at 28-35 lbs of line pressure for extended periods of time (street use) would be hard on any high psi pump. Just look at the monster 500 pump, it is really best suited for WOT racing. In my opinion it's kinda over-kill to use this pump for street use. While your sitting at a stop light (or at part throttle) it's building heat, dead headed & fighting to push un-needed 28-35 lbs of line pressure while idling or at slow cruse speeds.
Also, don't forget to use the correct higher pressure regulators meant for the 500's higher pressure output, this can save you from future headaches. A friend was fighting pressure problems when he first got a 500 pump. He tried to make his Holley and Barry Grant regulators work, but only Magnafuels regulators (meant for that pump) worked correctly.
460 street '66 Ranchero.......................finished someday.
460 race '70 Maverick..........................finished someday.
All 'glass Top Sportsman '69 Mustang......ummm, check back when I win big playing the Texas Lotto, or online poker.
page. Some ancient & newer local race video.
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