I haven't rebuilt the pump yet.

rebuilt my fuel pump with the kit from dsc motorsports and it worked great. shot to 8 lbs of presure and didnt budge at 2000 rpms will try in water this weekend hope it holds at full throttle.

Mansfield Mustangs has the kit for $37

http://mansfieldmustang.com/EngineFuelCarbp2.html

Thanks for the update. We'll be interested in how it does at WOT. I'd bet you'll be fine.

I have yet to source the rebuild kit part number C7AZ-9349-A but I did find a very helpful website that has a step by step rebuild with pics here http://www.428cobrajet.org/how-to-fuel-pump.html

that is the same site i used for refrence. and works great. wot holds 6 lbs nickersons said dont go under 5 lbs . so i orderd a 2nd one to rebuild the other pump and have 2 new ones. ps i did see a difference in psi at idle one time its at 6 lbs and next time its just under 9 lbs. other than that they run great.

well bad news guys. pump didnt keep up at wot. lost rpm looked at gauge and at 3lbs. backed off and went to 6lbs after 2ndaries shut. well time for electrics. good luck

Sorry to hear the pumps don't deliver enough fuel. What do you have for motors?

540s between 625 - 650 hp

Definitely needs more fuel than my HP525SC motors. The mechanical pump seems to be fine for my application. Currently my fuel pumps are as they came from Mercury. I haven't tried the rebuild kit yet. (I found that the erratic pressure reading I was getting on one of the motors was cuased by vibration. I had a mechanical test guage connected to the hard fuel lines at the carb. One cylinder was not firing!)

Clearly from what you describe there is not enough fuel flow at WOT.