LS_Turbo_Nova

Whats the limit of a single walbro 255 on a blow through setup? I always heard around 550whp with efi so I assumed with the lower pressure of a carb it would be more. Im having a problem going lean at the top end. I run a qft 750 blow through carb. I even removed the pvcr jets to make it just an open .130" pvcr holes75/98 jets and went for a test hit and about half track it goes lean like the pump cant keep up. This is a bone stock 5.3, s475 and 17-18psi. Has anyone found the limits of this pump? Oh yea, I also removed the fuel filter thinking that was a restriction.

Pop N Wood

iTrader: (1)

Did you try adjusting the air bleeds?

LS_Turbo_Nova

Yes. Even with the hsab's plugged, its going lean up top.

LS_Turbo_Nova

So I guess I was maxing out the fuel pump. I installed the AEM 380 pump and no more issues. I actually had to drop the jets down 10 sizes and the pvcr's back to .080. No more issues going lean at the top end.

47ford

Any way you could post a timing graph? Putting a 5.3 blow through together and will be running soon. Would like to have some sort of idea where to set timing..... I'm guessing your using a 6010 box or something equivalent ?