98 vortec carburetor swap

[Wintergreen98]

What carburetor?

Does this mean the truck runs good, then floods and stalls? Or does it mean the truck runs so crappy it won't stay running?

What is the fuel pressure? Does the carb still flood, or is that problem solved?

When adjusting the regulator it doesn't flood anymore but its like the carburetor isn't getting enough fuel to keep the bowls full.

 

[DamHoodlum]

Yes check your fuel pressure
Should be around 6 to 7-1/2
I run mine @ 7psi with a bypass regulator
Is it a 98 model truck? THESE pumps run at a different pressure

 

[Wintergreen98]

I replaced everything in the carburetor that come in a rebuild kit and adjusted the needle and seats. The motor was rebuilt as a 383 with a bigger cam. So I figured the 750 would do just fine on it.

 

[Wintergreen98]

Yes check your fuel pressure
Should be around 6 to 7-1/2
I run mine @ 7psi with a bypass regulator
Is it a 98 model truck? THESE pumps run at a different pressure

Yes this is a 98 truck

 

[Wintergreen98]

This is my current setup but the regulator is a little strange in my opinion. The guage reads really high but I hooked a pressure tester up to it and it showed the output at a little over 4psi

 

[DamHoodlum]

So yea, the 98 fuel pump is 62 PSI, The regulator you are using cant reduce it to 6psi consistently, especially since its not a bypass style.
You are going to need one of those $150 Holley bypass style to regulate it correctly.
PAY ONCE CRY ONCE

OR

depending on the fuel demand for your particular application you could use a 88-93 TBI pump (13PSI) with your existing regulator.

 

[red98]

I replaced everything in the carburetor that come in a rebuild kit and adjusted the needle and seats. The motor was rebuilt as a 383 with a bigger cam. So I figured the 750 would do just fine on it.

This is absolutely something to lead with - everyone in the thread is/was thinking you're carb swapping a stock 350 Vortec.

 

[PlayingWithTBI]

depending on the fuel demand for your particular application you could use a 88-93 TBI pump (13PSI) with your existing regulator.

The stock TBI fuel pump only puts out ~75 LPH and will only support ~230 - 250 HP. The EP381 Vortec pump is ~155 LPH and supports ~450 HP. Switch to something like this, YMMV

Holley 12-841 HP Billet Carbureted By-Pass Fuel Pressure Regulator

Holley® Billet Fuel Pressure Regulators are part of a complete line of fuel system products from Holley®. They are precision machined from 6061-T6 billet aluminum for strength and durability. They feature a black bright dip anodized body and a clear bright dip anodized top for corrosion...

www.speedwaymotors.com

 

[Supercharged111]

The stock TBI fuel pump only puts out ~75 LPH and will only support ~230 - 250 HP. The EP381 Vortec pump is ~155 LPH and supports ~450 HP. Switch to something like this, YMMV

Holley 12-841 HP Billet Carbureted By-Pass Fuel Pressure Regulator

Holley® Billet Fuel Pressure Regulators are part of a complete line of fuel system products from Holley®. They are precision machined from 6061-T6 billet aluminum for strength and durability. They feature a black bright dip anodized body and a clear bright dip anodized top for corrosion...

www.speedwaymotors.com

At what pressures? Lowering the pressure from stock increases the HP those pumps can support.

 

[PlayingWithTBI]

At what pressures? Lowering the pressure from stock increases the HP those pumps can support.

Yes, you're right but, the TBI pump is normally rated at ~13 PSI so, reducing pressure to 8 won't give you very much more. IMO definitely not enough for a 383. Where the EP381 is rated at ~62 PSI - plenty