I'm hoping that Dave N or others in the know can help with this.
When modifications have been done to a 502(509) mpi cool fuel engine(cam,heads,exhaust,ecm...) What is the maximum HP and RPM that can safely be handled by the stock cool fuel setup before starting to loose fuel pressure at full throttle?? I'm running 540HP at 5400 rpm and wondering if it is a concern.
Thanks for the help-

Sutphen,i'm in the process of modifying my 2000 502 intake and injectors. I bought 63 lb injectors from crockett,they are about 5/8 inch taller than stock injectors. I was going to modify the stock rail like what your describing but i chose to replace it with twin rails. i bought rail stock from someplace on th east coast but the i.d was .500 which made it hard to plumb so i found some rail stock w/.575 i.d which could be easily threaded w/3/8ths npt.I started modifying manifold and doing these rails before i had the injectors thinking it would help ensure good fuel delivery but with the injectors being so much longer than stock the stock rail wouldn't possibly fit. I'll post a couple of pics by the end of the week (a local machine shop is punching the holes in rail right now) Smitty

mjb,
I am not sure what the max HP/RPM would be for the cool fuel system. Maybe a Gaffrig dash mounted fuel pressure gauge would help answer your question.

Dave

I have electric fuel pressure gauges at the dash but I don't think they are very accurate. I added small mechanical gauges to the fuel rails to get a better reading.
Sutphen- I see the restriction at the crimp on the incoming line...sure is a small I.D. I'm not running a blower so I'm hoping it will still work ok. I need to check the #7 injector feed port like you mentioned. All of the paint melted in the left rear corner of each intake manifold. Maybe it was due to a lean condition at #7??
Thanks-

Mjb,not all rails have the restricted feed to #7 injector,i thought my 2000 would but when i dissassembled it was the same as the rest,Smitty

Mine is a '97. I checked last night and the #7 injectors are fed by a passage only a little larger than 1/8". I think I will enlarge that passage a little and hope new paint at the left rear manifold won't melt this time. I better keep a good eye on the #7 plug.

....and if you need bigger injectors, like 42lb out of a HP500EFI, let me know; I have a set I'd be glad to part with.