I have a LQ4, MP-T76, 60 lbs injectors and ZO6 cam. I just upped the bosst to about 14 psi and noticed that my AFR started going waaay lean on me (like 13.4-1) as I climbed in the RPM range. I tried making adjustments using my PE table but nothing seems to help. When I was runing about 6 psi things seemed ok. I could get 11.5-1 all the way with no problems.

I planned on adding a second pump I just didn't know how soon I would need to. Thanks in advance!

 

only about 500-550

 

I wouldn't push beyond 500rwhp with boost and a single walbro.

your very lucky you didn't pop your engine running that lean in boost, get a second pump in there !

 

Interesting I run one 255 with a msd boost a pump and see 17lbs boost on a built 383 (lq motor) with a ST80 turbo. My afr's are good, they respond to adjustments in the VE table (speed density). My 60lb injectors are close to max.

But my pump set seems to be keeping up, I'm surprised from reading the above responses.

 

What kind of dyno number are getting with this set up? I'm not running SD at the moment so maybe that is the difference.

 

If you had a fuel pressure gauge you would know you were running out of pump. Get a gauge, and if the pressure comes down you know the problem.

 

Save the time and trouble and get 2 pumps!!! Ask me how I know I have already been through this. One pump running out, only trying to push 8psi. and this was with a SD tune. Also had 60pd injectors but they were fine.

Setup I went with:
2 pump setup from Lonnies
I ran my own lines on feed and return -8 feed -6 return Weldon fuel pressure regulator, also changed fuel rails. Runiing 8pds without a glich at over 600RWHP

 

Don't really know, it's a stalled auto so the numbers are all over the place. A friend of mine has a twin turbo Z06 and makes 717rwhp on a single pump with a boost a pump.

speed density isn't related to your fueling requirements.

 

i wouldnt trust a single walbro past 500 flywheel HP.

But HP figures do vary around the world

 

he runs 9.70's @142 so I would think it's legit numbers. Not trying to say multiple pumps isn't a better set up.

 

Thanks for the info guys. The pump will be ordered tomorrow because I can't get the thing to respond no matter what I do.

 

The Z06 pump is quite larger than a 255lph Walbro. I regularly see them work at over 600rwhp. Higher with a boost-a-pump, but they are typically short lived at increased voltages.

The GSS340 Walbro pump is generally good to 550rwhp. Above this, it is a crap shoot.

If you are looking for a dual pump setup, I'll be gald to help you out.
Mine are completely assembled, tested & guaranteed to work.

Let me know if I can help.

 

Theres probably literally 100 different 255l walbros.....thats why youll see them cheap sometimes......with no model number. Just "255l"

Along long time ago.........the turbo buick guys tested the pumps a lot. The gss340 was good for about 650 chp, the 307 about 550.....

I ran a 99 camaro with a 340, 60's a 76, and z06 cam into the 16 psi area on 116 octane.

 

I have the 342 with a boost a pump

 

Can you run the z06 pump in the 99-02 Fbody tank / bucket setup?

 

I currently have the GCA758-2 in my tank now. After talking to the tech support guys this part number just gives you all of the accessories. GSS340 & GSS342 are just the pumps. I'm not sure how much the sock, wiring harness, etc. would cost separately. I may just order a second one like I have and be done with it.

 

Also another thing to note is how the fuel lines are setup , there size and also the pumps wiring/relay all plays a role in a fuel pumps output.

 

mine drops pressure to 43-46psi at 10psi of boost but then again it is 5 years old just ordered 2 new ones.

stock ls1 bottom end 317 heads ls9 cam no dyno numbers afr 11.5 @ 5200 then 12.8@ 6300

 

What do you presently have for a pump or pumps?