This isn't a post about Jay, so please don't make it one. Everyone has their favorite builder. Just like Chevy/Ford/ Dodge. I like Ponitacs and Buicks personally.
Whipper and Slomofo are just stating that people have options. Just as mentioned, Jay is one of many builders. Prices vary, turn around as mentioned can vary, skill level, shipping time and proximity also vary. The mods are pretty standard across the board if you choose to modify. Rebuilds only are even more standard. If the racers on Byuboyz don't seem to like him ,then thats their choice. Everyone has opinions and choices to make. Jay may be one persons choice as an engine builder, and there are lots of reasons to choose a builder. There are also lots of builders with videos and winning boats. Lots more builders weren't mentioned and I never once mentioned our own shop either. Glen Reynolds, Phil Conant, Performance Outboards (Ryan), Dale Hill, Eric Simon, Ron Anderson, Seebold Marine, Mumford in GA., John Marles in CA and so on. Many cut their teeth on F1 racing or are building winning drag boats and bassers.
BTW I would suggest that you have way too much initial timing on the motor in the video. You generally want less timing, a longer slide, and more air, so that the motor is crisper at idle. Lots of initial timing and less air tends to load up the motor. However, if you run a chip with 8-10% leaner bottom, that would allow you to run more timing.
