How much span are you getting from full vac to no vac? I'm using the smaller version of this designed for LT1 applications (p/n 13106). I've heard that the regulators with the larger (longer) body and spring have a greater pressure differential.

With no vac I have mine set at 32 psi and at idle with 22" of vac I get 24 psi.

Thanks; anyone else?

weaker spring set to 19 lbs with vac line attached it goes to 14 lbs. size of cam may affect. mine is 224/230 @ .05 114 LSA. I expected it to drop lower.

Yeah, I understand the effects of a lumpier cam. Mine has a 114 LSA also.

When I first switched to an external regulator, I had used one of the square looking Aeromotive units. The engine was smaller and had a cam with 110 LSA. It seems I was getting roughly 8 psi spread, but I could be wrong.

Currently am getting 6 psi spread. Guess I'll try one of the 13301's and see what happens.

If you have or have acess to a Mity-Vac pump some testing may be donw with it. Engine off, hot wire the pump on. Connect the Mity-vac to the FPR vac line. Then pump to 5" vac, check fuel pressure, then to 10" vac, read fuel pressure, and so on until at 25 - 30 " vac.

There should be a 1:1 change in fuel pressure to vacuum (converted for the proper units).

1 psi = 2.036 inches vacuum Hg

So at 10" of vacuum the fuel pressure should be lower by 4.9 psi

4.9 psi = (10 / 2.036)

RBob.

20 psi idle (45-50 MAP), 27 psi WOT (100 MAP)

Higher range spring.

I did what RBob suggested in order to calc the VAC v BPC table in EBL.
I ran 11psi at idle up to 20psi at WOT using 80# injectors.