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Nojdog 07-07-2012 08:46 PM

NEED HELP! Fuel delivery for l31 350 vortec conversion in YJ
I have a 1988 yj with 4 inch suspension, 3 inch body and 35 in tsl swampers. I recently put a 350 vortec l31 engine and transmission out of a 1999 yukon in it. I used aa saddle engine mount. I got a conversion adapter from jtr to match up my hybrid np231C/np231J with ss slipyoke eliminator transfer case to the 4L60 4x4 tranny. I custom built the transmission mounts located on the transfer case to the jeep skid plate so I could use the s10 tranny mts. It turned out really solid and fits perfect like the stock yj. A guy out of arkansas made a stand alone wiring harness out of my original l31 harness for $320 bucks. All I need to do now is find a cheap 23.5in rear drive shaft with u-joints on each end with the slip shaft setup in the middle of the shaft. I am very aware that I am gonna have to do a rear axle conversion at minimum to handle the tires and added power.

The problem I'm having is with fuel delivery. I got a 20 gallon tank/fuel pump out of a 1993 2.5 yj donor I bought. I really need to know if the 2.5 liter pump is going to produce the 66psi I need to run the L31 vortec engine? I'm not sure, but I heard a rumor that the L31 has a fuel regulator on the fuel rail on top of the engine. Also...will the stock fuel pump in the 1993 2.5 produce the psi I need? If not, is there another pump I can replace it with in the tank. My friend told me Walboro makes a pump that should fit, but I don't know the part number! I don't want an out of tank fuel pump. PLEASE HELP! I'm ready to get this beast rolling!:eek:

2xs 07-07-2012 10:20 PM

The pump is set up for a 2.5, even if it could produce the pressure, you will have a volume issue, that 350 drinks WAY more juice then any 2.5L

Perhaps use the 2.5L pump as a primer for a frame rail pump....

stykthyn 07-07-2012 10:29 PM

Walboro 255

2xs 07-07-2012 10:31 PM


Originally Posted by stykthyn (Post 2556889)
Walboro 255

Thats an in-tank pump, is it a direct fit in place of the Jeep in-tank pumps?

Might have to use that myself when I do my Vortec swap.

stykthyn 07-07-2012 10:34 PM

In tank pump. You need to modify the connectors for the wiring. I ran one on a warmed over ls1 and it had no problems. They can support 500hp or so.

Ibuildembig 07-07-2012 10:37 PM

Nope, not even close to being a direct fit. I bought one and decided against a bunch of mods to make it work and with some buddies who run them with 50 percent success in their street cars it wasnt something I was willing to take a chance with. 66psi is gonna require a pretty big pump.

stykthyn 07-08-2012 07:43 AM

the vortech trex kit is a decent piece. professional products makes an electric in line pump but I really cant stand professional products.
To be honest though there is going to be be some fabrication or the use of an install kit to make an aftermarket pump work.

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