zupmanZ28

Heres the setup before i describe the problem: 350, TFS heads, rpm intake, Demon 750dp, Holley mech. fuel pump (110gph) and a diaphragm regulator, 3/8" lines. t56, 9" with 3.89's

Now the problem: When i floor it in first and run it though the gears, i hit 3rd gear and it leans waaayyyy out. Hit 4th gear and it's totally fine. If i keep my foot on the floor during shifts it doesn't lean out, but i i let off even the slightest bit, it leans right out.

What are your thoughts on this? I'm beginning to think maybe the pump is tired. I've had this same basic setup for about 2 years, and the problem has just started in te last couple months.

I don't really wanna go electric, so i was thinking of a victor mech. pump, and upgrading to 1/2" lines.

Am i running in the right direction here or am i way off?

droppedgmc

the 3/8 line is plenty of fuel. maybe your pump is tired, the spring my be starting to float @ higher rpm's. also can maybe change the rear jets

a71stangbeater

how do you know it leans out in 3rd and 4th but not in the others? Generally though, leanin in High rpms is a matter of jetting. You can also run a hand held fuel pressure gauge from under the hood and tape it to the windsheild, then have a friend watch the pressure when you're banging gears, that will tell you whether its your pump or the carb.

zupmanZ28

AF guage says lean, plus you can just feel the loss of power. The thing that boggles my mind though, is that once i bang 4th it's totally fine

a71stangbeater

unless thats a wide band o2 they're not very acurate other than to make a cool lookin flashy thing on your dash, and if it is, what is the Ratio?

Also the difference from 3-4 on a t56 is pretty long, so you motr will be bogged a bit more, which could more time for catch up. Try that test with the pressure gauge first then go from their, at least you'll know whether its pump or crab related

zupmanZ28

its not a wide band but trust me when i say it's leaning out. you can feel the loss in power when it happens

I"m gonna look for a fuel pressure deal and see if can find out whats going on... maybe i'll bump up the jets a little more in the back, but they're already up there in size. i think i'm running 90's right now

Eric

a71stangbeater

do you have a chasis dyno around where you are, thats sounds real big for your setup. dynoing it and putting a wide band on it can tell you exactly what and where in the rpm range your problem is, or your plugs white?

zupmanZ28

i thought the jets were a bit large for it too, but it worse with smaller jets in it. I don't have a reputable dyno shop within 50 miles of me. I know that would help a ton with the tuning aspect. However i don't think the starving in thrid problem is due to tuning, something is downright wrong somewhere

Eric