Hey Spud, I sent you two hilborn pumps after last season so you could check and flow them. I have lost the flow cards you sent back with the pumps. I remember they flowed around 6.5 gpm but I would like to know what rpm this flow was at.
Our tags show the flow at:
1800 pump RPM @ 50 PSI
4000 pump RPM @ 100 PSI
Your 6.5 GPM number was the 4000 pump RPM figure (8000 engine RPM).
Our flow tags are now decals so you can stick them in your log book, in the lid of your toolbox, inside the door of your trailer...someplace safe.
Also I have some nozzles in my hilborn that some say are too big. They have 18BS stamped on them. It's a hilborn 3 piece 2-3/4, sbc 406 with iron eagle 23deg that flow pretty good.
Could this be too low of a pressure system?
Some people run much smaller nozzles in a motor that size, but most who do that don't spin the motor up very high. Those nozzles will work just fine for you, just at a bit lower system pressure. If you're only hitting say 7000 RPM at the top end, 12's would be better. If you're spinning to 9500 on a pass, then 18's are just what you need.
The "18" means they flow .18 GPM of .792 SG liquid @ 30 PSI. The "B" means they were meant for a turbo application and the "S" means they have a screen tip.