I was at the dyno last week and I went very lean(almost 15:1) and my fuel pressure stopped climbing once it hit around 50psi. I am running a P1SC w/ about 10#s of boost on a mild 350. I am using the ATI FMU, 30# injectors, ATI Booster fuel pump and stock in tank fuel pump. The FMU was screwed all the way in, so the owner of the Speed shop thinks I need an aftermarket in tank pump like a Walbro 255 H.P.

What do you guys think? Do I need an aftermarket in tank pump, and if I get one should I ditch the ATI Booster Pump. Any help or input is appreciated.

Im used to seeing this happen in one of two cases, when someone is sold the idea that there will be no problem without the extra pump ATI includes, if you just get a really nice in tank.

The other is if the in line is used but the in tank one is failing.

to play it safe you can go with both...

Thanks Tom, I guess I will replace the stock in tank pump. Any suggestions? Are there any direct replacement pumps for our cars, or all they all universal? By the way how the B4C coming along?

Yeah I would say to get one of the nicest aftermarket 255 LPH in tank setups to add to your inline. This way when you ditch the FMU for a ECM style boost referrenced setup you can possibly ditch the inline.

The B is up and running it does some weird oil pressure stuff which I attribute to the higher oil temps and the hydraulic rollers somehow, but its within spec. The chip tuning is the part I have to do now, I bought a laptop but there is a delivery delay so far. It has so mch torque and power right now even with everything so haywire in the chip.

The Z machineshop wise is nearly done. I just procured a professionally built transbrake th350 and a 10" 3200 stall converter. I used to build these baby's my self so a once over is in order since he killed his 4500 stall converter on it. but it looks beautiful on initial inspection. ETA fo the Z is this winter if my job stays in this area.

Wow, good luck w/ tuning that beast and thanks for the help.

Did you fix your problem?

Well, a Walbro 255 H.P. fuel pump is in the mail as we speak. I'll probably get it installed in the next couple of weeks, then I'll have to get it on the dyno and wideband to see if my problem is fixed. I'll keep you posted.

Thanks!

I'm not seeing the increase in FP as I should and I'm also going lean....