Is it possible to make a stock fuel pressure regulator into a vacuum AFPR? If I were to just tap into the side of the can part that would decrease the pressure inside and lower the pressure...not what I want. The reason I'm asking is because I'm cheap, broke, and have the holley TB which is a different regulator than the GM piece.

 

You don' tneed it with those big Holley injectors and WINALDL. Please post your spark curve on your other "drag talk" post and I'll help.

Please try spark changes and WINALDL tuning before you waste your time with the AFPR. My combo is more radical and runs so good that you gotta try what I did. PLEASE?

 

I haven't seen the afpr on your Holley, but even if it could be done, the spring would need to be replaced. The vacuum will reduce the spring force which will dramatically reduce the fuel pressure at idle. Test the spring force of your existing spring by using a bathroom or postal scale. Measure the free length of spring. Then put the spring on the scale, put a tape measure beside it and a credit card on top of the spring. Then press down. Record the deflection and the weight readings. This will tell you the spring rate in lbs/inch of deflection. For example: free length of the spring that comes with the vafpr is 1.875", it deflects .5" at 10 lbs. This equals approximatly 20 lbs/in spring rate. The free length, spring rate, OD, ID and wire diameter of the spring are needed to make an educated guess when chosing a new spring. Good luck, Lon.

 

If you can program PROMS, you only need the the AFPR if you have injectors misfire issues at low engine speeds/idle. ie, if you need to bring down the FP so you can bring up the firing time (pulse width) of the injectors so that they actually fire and not misfire...

ie, no PROM tuning can fix the problem BUT you won't have that problem with 80-85pph Holley injectors run at the rated 15psi. JP should be good.

 

The reason I want to do it is because I'm running the holley 65# injectors and we all know how they don't like to work with high fuel pressure for long periods of time. If I could make it so the vacuum would increase the fuel pressure only under WOT operation or anything above 50kpa then that would be great. I could run lower fuel pressure driving around with a light foot and then when I needed it I would have the more pressure for the whole 330hp. I'm already doing a bunch of eprom burning and fastb, when my laptop finishs charging it'll have those spark tables tested.

 

How'd you end up with only 65pph injectors??? maybe you could swap them at Holley direct???