327Chevy

I've got the new engine in. It runs...barely. That was to be expected because I haven't done any tuning yet. Seems like I need to set up the fueling before I start tuning. I'd like some thoughts on my fuel system. I would like to base this on 375 HP.

Right now I've got the original GM TBI unit on it, but I will be installing the holley unit in my signature.

Specifically, I am interested in 1) a fuel pump recommendation and 2) a way to get 25 psi-ish out of my holley tbi unit's regulator.

1) I have heard of people using TPI pumps, walbro 190 lph, walbro 255 lph pump, etc. What is the most cost effective, direct fit way to support this pressure and horespower level.

2) I know my holley TBI has an adjustable regulator but I think I need more pressure than it will provide for the 375 hp level, supposedly it will pressure up to maybe 20 psi. I have heard a lot of guys talk about replacing their pressure regulator springs, but this is generally for stock GM TBI regulators. I read one post where a guy talked about using a part (plunger?) from a later model GM 30 psi tbi regulator in a holley with the existing holley spring and getting low 20's - low 40's adjustability. Also I have heard about variable pressure regulators but have heard a special ecm is required. As in not my 063 or the easily swappable 746.

Thoughts on all this? Thanks for your help.

327Chevy

I did some more thinking on the fuel pump.

375 hp* .5 bsfc / .85 = 220 lb/hr

220 lb/hr / 6.175 lb/gal = 35.63 gal /hr

35.63 gal/hr = 134.9 liter/hr

This would be the minimum required fuel flow to supply the engine at max HP. From the autozone website I am looking at a stock replacement TPI pump (E3210) that flows 40 gal/hr = 151.4 liter/hr at 65-90 psi. I'm sure other sources have similar pumps.

That looks like adequate flow and more than enough pressure. Has anybody got experience with a stock TPI pump being inadequate?

Thoughts?

RFmaster

Just make sure that you also have volume in addition to pressure. To feed 375 HP you'll need 3/8" supply line without too many bends or kinks or adapters. Return line should be similarly sized (3/8 or 5/16"). Look into mid 90's TBI pump used with either TPI, 4.3L CPI or Vortec engines:
TPI, MPI = Delco EP-241 (E3210 Airtex )pump should be able to deliver 40 GPH at 65-75 PSI
Vortec, LS = Delco EP-381 (E3270 Airtex )pump which supposed to to deliver 50-60GPH at 60 to 70psi.

//RF

327Chevy

That TPI pump (E3210 Airtex) is the same one I was looking at. My car has the stock diameter fuel lines for 88 TBI 305. I will look tonight to see what size they are.

Thanks.

Ronny

iTrader: (1)

The TBI spring that is in a GM 1995-1996 7.4L I believe is ran at 26-32 lbs FP. It is orange in color. To obtain you will need I suspect to purchase the entire regulator. Not sure.

If you can swing it the Aero unit is ideal at 20-60 lbs FP plus supports VAFPR which is desirable when FP is in excess of 22 lbs IMO.

327Chevy

Thanks Ronny,

Can you tell me more about the Aero unit?

I have heard that vacuum referenced regulators won't work with the older computers like my 063 or the 746 I may swap to. Is this correct? If I need a better computer, do you know which one would have this feature? Probably EBL, right? Any others?

It sounds like it's doable with just the 1995-1996 7.4L regulator parts and my existing computer, just not preferred. What would I be giving up with this approach - is it idle quality? Modifying the existing regulator seems simpler, I might go that route if it will get it done.

Thanks again.

Ronny

iTrader: (1)

Aeromotive 13301 $116 at summit. comes with low press spring and high pressure spring. When the VAFPR is enabled it reduces the FP at idle allowing a more stable idle(lower PW). I run 24 lbs WOT and 14 lbs idle. Requires an ECU that supports VAFPR. EBL does just that. BPC is VAC based. dynamicefi.com for more info. I suspect Megasquirt ECU will do same. I thought GM VAFPR was used on marine engines. Not sure which ECU they used but it supported VAFPR. I think GM crate auto engines(7.4L) did likewise.

327Chevy

Thanks for the tip on the VAFPR, but I cheaped out (for now). I ordered stuff to measure the pressure and I have a stiffer spring on the way. This spring is supposedly going to give me 24.5-29.5 psi adjustability, but has not been tested in a holley unit. We shall see. Cheaper regulator and it may not require EBL. EBL looks like it rules but is not in the budget at the moment.

I will test it and let you guys know how it works out in terms of pressure. It'll be at least a week until I have results.

I also picked up an Airtex E3210 (TPI) pump today.