Chevy Impala SS Forum banner

21 - 30 of 30 Posts

·
Premium Member
Joined
·
609 Posts
More trivia.

LT1 pump , free flow with about a foot of 3/8 hose , 4.52 amps
Peak amps on start up with no pressure head 4.64 amps
Again methanol, not gasoline
PCM current draw at rest, both batt and ign circuit 0.47 amps

96 lt4 295-305 ish at the wheels
Awesome - Thanks for sharing this! Was the pump in Post 12 a stock LT1 pump?
 

·
Premium Member
Joined
·
5,564 Posts
One thing about the relay and oversize fuel pump wire kits.
They work well and I get why they are built with the relay at the rear .
This so they are completely bolt in- plug in.

I would submit , if a guy is a do it yourselfer, I would have the relay at the front of the car near the fuse box
This so the large feed wire running front to rear is only energized when the pump is running, not live all the time.
Now if you have a rear mounted battery, rear relays such as I have make more sense.
 

·
Registered
Joined
·
2,037 Posts
That is what I did. My new FP relay and fuse lives right next to my fuse box and I ran a new 10ga wire back to the tank, down the pass side frame rail.

Brian
 

·
Registered
Joined
·
1,433 Posts
Discussion Starter #25
Lots of good info in here



FWIW I think you'd be fine with a Walbro 255 with pretty much any N/A Lt1 setup you could dream up except for the most extreme setups. At 400whp I think you'd be fine, but if you wanted a bit more wiggle room you could look into an Aeromotive Stealth 340 pump. Pretty sure you could make one work either drop in or with very little modification to the bucket/hanger. Knowing with how you push your car and the type of racing you do, I would upgrade the pump and harness regardless of whether or not the stock pump could handle the power levels. Reason I say this is because your car probably spends a significantly higher amount of time at higher RPM's than the average street/strip car and the pump is seeing higher pressure/load more frequently and for longer sustained periods of time. I'd rather be ripping around a track with a walbro 255 working only half as hard as it could be than having a stock pump going max effort to maintain fuel pressure under load.

With the 255 drawing more amps and the fact that your car sees such frequent race track use with sustained/frequent high RPM's could mean more heat in the harness than the average street car would see running that same setup. Heat, like length, also has an effect on particular wire diameter's ability to handle current. May be overkill, but if it were my car running say a 400-450whp N/A stroker being frequently raced, I'd do the following.

Walbro 255
10 gauge power
10 gauge chassis ground
Stock fuel lines should be fine.
Regulator of your choice

I doubt you really need 10 gauge, but can't hurt to upsize.

Only other thing I'd think about is fuel control, but if you aren't having any starvation issues now out on the track I assume you only run it with a decent amount of fuel in the tank? Wouldn't want to be leaning your new motor out.
Good notes on the wiring upgrades. I'll definitely look into that.

Does the 255 Walbro drop right into the stock sending unit otherwise?

Fuel control is somewhere on the list as well. May do a smaller custom tank in the stock location, as I don't particularly like the high CG of a trunk mounted fuel cell, nor do I want to give up the trunk space - as funny as that may sound for a "race car" - I still load it up full every time I drive to the track.
Currently, I run the tank FULL up as much as possible, as it prevents fuel starvation, reduces slosh, and hopefully helps keep the pump and wiring a bit cooler. It does also help with rearward ballast/balance, but it would be nice to be able to lose some fuel weight and then try to get similar weight out of the front of the car....
 

·
Registered
Joined
·
7,140 Posts
The disadvantages of more pump than the motor needs are they demand/consume more amperage ,and tend to have shorter lives. All that additional fuel just goes back to the tank ,warming up that fuel. I've had my Impala for 25 years ,and 170k miles. Replaced one fuel pump over 10 years ago. Once you have something that deliver enough fuel. The ability to deliver more is of no real advantage ,and likely come with built in drawbacks of their own.
 

·
Registered
Joined
·
2,416 Posts
Good notes on the wiring upgrades. I'll definitely look into that.

Does the 255 Walbro drop right into the stock sending unit otherwise?

Fuel control is somewhere on the list as well. May do a smaller custom tank in the stock location, as I don't particularly like the high CG of a trunk mounted fuel cell, nor do I want to give up the trunk space - as funny as that may sound for a "race car" - I still load it up full every time I drive to the track.
Currently, I run the tank FULL up as much as possible, as it prevents fuel starvation, reduces slosh, and hopefully helps keep the pump and wiring a bit cooler. It does also help with rearward ballast/balance, but it would be nice to be able to lose some fuel weight and then try to get similar weight out of the front of the car....

I THINK the 255 does if I remember right, I can't remember making any modifications to the hanger or bucket but if there were, they were very minor.

For fuel control, you may want to look into an Aeromotive phantom setup. I run a dual pump phantom setup but there are also single 255 and 304 pump versions. It includes a hat/hanger and you keep your factory sending unit just for the fuel sender itself. It's an easy install, just cut a hole out in the factory tank, dremel out some of the old bucket out for clearance of the foam baffle ring and the automotive pump setup drops in inside of a foam ring that you install into the tank. It's all ethanol compatible, and the return feeds into the foam bucket for more effective fuel control and ensures the pump pickup is always submerged. There are a few demonstrations of it on youtube, and i've heard overall good results from guys using them as far as fuel control goes.

Mine works great, but I also haven't really pushed the car to any limits yet. The only disadvantage is that the hat sticks up maybe 3/8ths of an inch plus the fittings exiting the hat, so I had to cut a hole in my trunk floor and build a slight raised access hatch to clear it. I probably could have just used spacers to sit the gas tank a little lower and avoided that but I kind of wanted the ability to remove/test/trouble shoot the pump without removing the tank, especially with a twin pump setup. I'll post some pics here tonight.

You could also run a swirl pot/surge tank setup using your stock pump to feed it.


As for what 1slow96 said, I agree to an extend but plenty of people run 255's in daily driven cars with stock fuel lines and I haven't heard of too many issues with longevity of the pump or fuel heating up excessively. We also have large tanks, so 1/4 of a tank in our cars is a lot more fuel to be circulating than 1/4 of a tank in a car with a 10 gallon tank which means it'll take the fuel longer to heat up. I run a Magnafuel Pro Tuner 750 (big pump for my procharged/EFI/E85 setup) with no pump controller on my 70 challenger with a 15 gallon fuel cell and I don't even see issues with fuel temps or pump temps on that car doing hour long local cruises in the summer on pump gas or E85. While it's not good to run more pump than you need, the risk of running less pump than you need is a lot worse IMO. That's not to say you should run an A1000 on a bolt ons car but I think a 255LPH is a pretty standard pump to be running for a mild-moderately built small block setup on a street/strip car. You shouldn't have any issues.

Also different conditions for a daily driver vs a track car. Daily driver spends hours idling just recirculating fuel, being driven for extended periods of time.A track car is spending more times at higher RPM's with more fuel demand so fuel is actually being used, less hot fuel being sent back to the tank hot to circulate through the pump again and the car probably isn't being driven for hours on end unless you're doing the Indy 500 haha
 

·
Registered
Joined
·
2,416 Posts
Yeah, just wanted to underline that :)
Yea, the swirl pot is a really good idea and probably the most effective way of ensuring you never starve the pump. Sometimes I wish I went in that direction instead.

The only benefit to the phantom setup I saw was that I added enough extra wiring, accessories, things to go wrong already so I kind of liked the idea of just narrowing the setup down to two pumps instead of needing the factory pump to feed the pot and then twin pumps to feed my boosted setup.
 

·
Premium Member
Joined
·
1,278 Posts
If i remember correctly the racetronix upgrade harness powers direct off the alternator giving the pump a voltage boost as well
 
21 - 30 of 30 Posts
Top