I agree. The Shaker unit kept a lot of heat under the 2 eddys on my hemi challenger clone & left me stranded many times in the 80 - 100 degree Reno summer heat. Fuel lines were so hot, I could hardly touch them.
Factory vapor separator & 1/4"return line solved the problem immediately. Kr*p ethanol laced gas (especially chevron) exacerbated the problem & before the vapor separator install, a few gallons of leaded AV gas or 110 leaded was a temporary fix. THEN, aftera few months, lock returned & on measuring the repop mech pushrod, it was short by obver 1/8" & wiped out the cam lobe. Electric pump had to be installed. Also, had vapor lock in the 70 383 Magnum in my power wagon.
No return line with mech pump. Float was out of whack, so we readjusted it but no permanent fix. Pulled the REPOP pushrod & it was also too short. A reputable engine builder told me years ago, always use an oem pushrod since some repops are too short. Gist of this is if your pushrod isn't short & float levels are correct, and if a few gallons of leaded race gas stops the lock, install the factory vapor separator & return line.