OK, WOT run, AFR is about 12. Looking at my EBL log, at 4600rpm, the sPW is 6.3 and the DC% is 98. No matter what my BPC is, and even though the AFR is where I think I need it, the injectors are static, right?

I ask the BPC question because I calculated it to be 96, but I couldn't get enough table headroom at WOT. Now I'm using 108

I'm running the Holley TBI with their injectors (new style) at 23psi. Their regulator doesn't allow me to go any higher because turning the pressure up makes it jump to 30. If the injectors are static, what can I do? I don't believe Holley makes larger injectors for this TBI, or I could switch. I also thought about converting to a VAFPR, but I have no idea what these injectors will run safely at.

I have some engine mods done (in sig), but it's still a 350. I figured the Holley would be more than enough to supply the fuel.

Anyone have any suggestions reguarding this set up?

 

I believe Holley does or did make a larger injector. Anyway they did make an 80(rated at their FP which I think was 20?) back about 4 years ago when I inquired as to a new Holley unit and swap injectors out to 80. If you are seeing 98% in PE for DC yea it looks like you are maxed. I heard that AE requires more DC than PE? Any chance you can find a stiffer spring on step up? One of the sponsors(top down solutions?) on this forum offerred one for stock GM unit. Other option is the Aeromotive FPR which is so easy to adjust and swap springs..

 

Those 80# injectors you are talking about is just their 68# injectors at 21 psi. Those are the injectors I have, but I'm already running them at 23psi. Is it safe to take them higher with a new regulator? A VAFPR has been on my list for a few months, but I want to make sure I'm fixing the problem without using duct tape and a hammer if you know what I mean.

 

It may be that the fuel pressure (FP) is dropping off. You posted that when you try to increase the FP it jumps to 30 psi. Most likely bottoming the FPR spring and max'ing out the pump. Then running at 23 psi only gives 7 psi of head room.

With fuel pumps, increasing the pressure reduces the flow. Then as more flow is required (when the injectors are open more often), the pressure drops off. It may be time for a Walbro 190 lph pump.

If you have a FP gauge observe it as the throttle is wacked fully open. Can do this at a stand still in neutral. Any dropping of the pressure, even a half a psi, will show that the pump output is dropping off.

RBob.

 

I remember the Holley catalog offerred in the dual 2.00 inch TBI a 65 lb injector. I called them and asked if they would swap the 80 lb optional injector again in catalog with a diff part # and they said not. only option was to buy the unit and end up with an extra set of 65 lb injectors. this was 4-5 years ago. i dont think Holley offers the 80 any longer. not sure if a GM pod will work on Holley TBI base to allow a bigger inj. I think Fast355 used GM 65 at very high pressure(30 lbs+) as did others. Not sure if Holley is up to task. dont know.

 

The pressure jumps to 30, and that's as high as my gauge goes. At 23psi I can blip the throttle and the pressure drops a half a pound then immediately goes back up. The pump is a Walbro 255 installed about 4 months ago, so I hope it isn't the problem. I could adjust the BPC for the higher pressure, but I'm guessing that's not a good idea since the regulator, at that point, isn't regulating?

Someone told me that the stock injector pod will work on the Holley with some modifications. Maybe I'll just get a new regulator and run the Holley injectors until they stop working, then do the mods to make the stock pod fit.

 

OK, the FP could easily be going higher.

At 23psi I can blip the throttle and the pressure drops a half a pound then immediately goes back up. The pump is a Walbro 255 installed about 4 months ago, so I hope it isn't the problem.

There may be a leak between the pump and the outlet pipe of the tank. If there is a turtle (pump damper) they are known to leak. If it is a rubber line in place of the turtle, it could have split. In any case a blip should not have the fuel pressure dropping off.

When the regulator spring is bottomed the regulator is no longer returning fuel to the tank. So the pump dead heads, which for a port type pump (positive displacement) is typically north of 60 psi. And can be as high as 100 psi.

I could adjust the BPC for the higher pressure, but I'm guessing that's not a good idea since the regulator, at that point, isn't regulating?

Yep.

Someone told me that the stock injector pod will work on the Holley with some modifications. Maybe I'll just get a new regulator and run the Holley injectors until they stop working, then do the mods to make the stock pod fit.

If the Holley is the newer style with the Delphi injectors (connectors come off horizontal) they probably won't go bad.

RBob.