I took my tank out, because car has sat for a few years
It had a Racetrinics rxp269 pump in the tank
I can't find this same pump
They offer either a rxp255 or a rxp340
Car made 400 horse to the rear wheels
(with a junk homemade CAI and the transmission not shifting correctly)
Going to replace the CAI and we think the trans is fixed (found 2 wires crossed in the trans harness)
Was thinking about bumping up the cam a little (but I don't know to what)
It has a Comp Cam now: 613/620 lift, 227/235 Dur @ .050 and a 113 Lobe Sep

This is a street toy
Would like to be around 550 @ the rear wheels

Any and all help would be greatly appreciated
Thanks,
Rob

 

You should be fine with the 340. Especially if you anticipate a little power growth....

 

IMO you will need to upgrade the wire harness if you install a pump other than stock. Racetronix has a kit for a single 255 and/or 340. The larger wires and relays in the wire harness maximize the efficiency of the pump over the less than adequate stock wire harness. The kit will also come with an upgraded bulkhead connector. Make sure you replace the stock connector with the new connector.

http://www.ws6project.com/user_stor/...oducts_id=8399

IMO you will also need larger injectors for 550 rwhp. Start will 42's. With a D1 procharger at 8 lbs of boost it made 500 rwhp with the 42's I switched to 60's when I upped the boost with a smaller pulley It made 565 to the rear wheels and was well within range for the duty cycle with the 60's. There's not much difference in price between the 42's and the 60's.

 

Thanks for the reply
The motor isn't a stock LS
It's a iron block 6.0 that's bored .065
With CNC ported GM L92 heads, intake and LS3 injectors (whatever size that is) with 92 mm throttle body
With 6.125 rods (add the previous mentioned cam)
Forged rods and piston, but stock crank

I do already have the racetronics wiring harness for the fuel pump

 

should be good with 340

 

Since you will have to remove the fuel tank fuel pump assembly and you have the upgraded harness, I would make sure to double check that the bulkhead connector was upgraded with the higher capacity amp bulkhead connector. It's easy to tell if it was replaced with the upgrade as two of the pins on the connector will be nearly double in size. It's only about $10. With the 340, it requires more amps than the original stock 255 pump. Check with tech support for the correct PN.

https://www.racetronix.biz/p/connect...80-150/rcs-027

Note: years 1999 - 2002 will have the upgraded bulkhead connector in the new harness kit. Year 1998 has the yellow bulkhead connector. The pin size on it are much smaller and are borderline capacity for the 340 (14 amps).

 

A 255 will support that engine. The 340 uses an upgraded harness and different fuel tank bulkhead with higher current ratings, so definitely need to decide up front because wiring is not the same. The harness changes are more than just connector type at bulkhead, the whole thing is uprated.

Other changes are 340 does not use stock regulator so the fuel lines have to be rebuilt. The 255 is definitely the easier 'drop in" between the two choices.

 

Agree. Racetronix states the 255 kit will support up to 600 rwhp. As I said in an earlier post the 255 kit easily supported 565 RWHP (boosted) with 60lb injectors at 8 to ten lbs of boost (Mustang Dyno) on my Procharged D1SC Z28 at less than 80 percent duty cycle.

https://www.texas-speed.com/p-2358-r...02-f-body.aspx

My last post was a reminder about the bulkhead connector. OP didn't say what year upgraded harness was installed. No doubt there have been changes since 2005.

Note: with the 255 OP won't have to worry about overpowering the stock regulator either. Even so, I would replace it since the original is probably still in the assembly.

 

Dlandsvz28 question for you. I’m putting a 5.3 LM7 in my 94z28 and I’m using the stock LT1 fuel lines. I know I need to find a 97-98 fuel rail for the lines to work. Planned on 60lb injectors. Adding a blower on the engine probably procharger this time around as had vortech on old LT1 engine. I want to have 600rwhp and I have read what you said about the 255 and what Racetronix says. 600rwhp with the Hotwire kit. I have a Walbro 255 that’s been sitting dry for years inside the tank so I’m sure it’s no longer any good? Was wondering if I should do a 340 instead of a new 255 pump then..

 

A 255 L/hr will not support a boosted engine at 600 RWHP. There isn't enough pump flow at the increased rail pressure needed to overcome the manifold pressure.

I gotta call BS on supporting 600 RWHP naturally aspirated too. More like 600 Hp crank. Mine didn't even make it that far before fuel pressure began to drop.

 

Racetronix 255 fell off at 4,000 rpm's on the LSX 427 and 93 octane.

 

Huh wonder how they claim there pump hits that hp level? Walbro told me the 340lph pump is good for 600rwhp maybe even 700 can’t remember exactly but remember the rep telling me 600 for sure.

 

I thought the nominal rating was 550 Hp but it's actually 500 Hp on the Walbro literature (GSS series 255 Lph pumps), https://walbrofuelpumps.com/ How that rating is developed I don't know. Clearly there is design margin in there.

The label rating of 255 Lph is developed at 40 psi. You've got to look at the flow curve (flow vs. pressure) to see what it does at your desired operating pressure, https://walbrofuelpumps.com/universa...uel-pumps.html

Reading the chart, the GSS 255 Lph pump delivers about 60 gal/hr at 60 psi and 13.5V. Gasoline weighs about 6 lb/gal and the engine uses roughly 0.5 lb/hr per horsepower. Running the math that comes out to 720 Hp. That might be where the idea of supporting 600 RWHP comes from? I don't know, just guessing.

But in the real world there has to be design margin to cover your *** because running lean can cause detonation, and detonation melts metal. It's a risk you can't afford to take. You want to make sure the fuel pump is sufficient in case system voltage drops to battery voltage (alternator output not enough for some reason). That's why Walbro provides you a 12V curve. It's not typical operating condition but sometimes crap happens. That same pump makes only 50 gal/hr at 12V which comes out to around 600 Hp. Okay, so you can safely cover 600 Hp, right? Well.... maybe. Fuel lines and filters cause losses too. And voltage losses in wiring (B+ and ground runs) lower operating voltage across the pump. Results will vary.

If you go up to a 340 Lph pump then be aware the stock F-body filter becomes a notable restriction above 270 Lph flow rate. Lingenfelter bench testing shows C5 filter doesn't flow any better. I put a C5 filter on my car and fuel pressure isn't steady at WOT. One of these days I'll be reworking to a full return line with regulator at the engine. Honestly, Racetronix advised me not to use a C5 filter but I went with internet wisdom instead because it was easier. Don't be me. Do it right.

 

Great explanation for all us thanks and yeah guess it is possible then for 600hp.