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When looking at numbers north of 400 rwhp, I recommend a regulated return system with larger fuel lines and get rid of the check valves in the heads. I built my own with an Aeromotive adjustable regulator, AN PushLok fittings, and synthetic nylon braided hoses with Otiker clamps. The change to a full regulated return, over my homebuilt CCK (similar to FRx), netted me ~35 more hp and 100 ft-lbs tq.
Robin and I's hp and tq numbers are very similar; and our injectors flow about the same rate.
Robin, did you make your own fuel return or use Clays FRX?
Chet
My fuel return is the CCK that was produced by Dino Fuels Alternatives. It was the budget (allthough high quality) fuel return at the time. Still functions just fine and had an 1/8" NPT port where the two fuel rail crossover lines tee together that made it a snap to plumb in my fuel pressure gauge. Instead of measuring fuel pessure at the fuel bowl this arrangement lets me measure the fuel pressure post injectors.
DFA specialized in products for WVO as a fuel and was bought by a larger company and the CCK is no longer available. I've had the CCK installed for about five years. If Clay's FRX was available at the time I would have gone with it, much easier install.
Thanks Robin, I have Clays right now. I didn't take out the check valves as mentioned above in the stock locations.
Chet
I've still got the check valves and unless you're going for huge HP just leave them alone. Post injectors I have 70 PSI at idle and 65 PSI at WOT so they don't seem to be all that restrictive.