how to mod a Holley 4bbl for turbo charging

[280zex]

ok this is my mods and adjustments for a Holley model 4150 390cfm 4bbl double pumper for turbo charging, blow thru style

 

BUY the blue reuseable metering block and fuel bowl gaskets along with the teflon fuel bowl screw gaskets, your going to need them.

 

Main Body Mods:

Mill off the choke horn, fill in the linkage holes in the main body from the choke. use fuel resistant epoxy

Block off the secondary side vacuum channel for the power valve in the bottom of the main body.

Block off all 4 high speed air bleeds.

 

IF you do not have adjustable low speed air bleeds: remove the brass inserts (air bleeds) from the 4 low speed air bleeds, drill and tap holes to accept Idle Feed Restrictors with a 1/8 tap. This is a less expensive mod because standard size low speed air bleeds cost more than the smaller sized idle feed restrictors. AND most hot rod shops keep Idle feed restrictors on hand, so hopefully no special order stuff ;-)

 

Primary side low speed air bleeds are 77

Secondary side low speed air bleeds are 52

 

Metering blocks:

I use 2 primary Quick Fuel no vac port metering blocks because I need a standard power valve for the primary side, and a modified Boost regulated power valve (BRPV) for the secondary side. Google hangar 18 mods for BRPV mods, or goto theturboforums.com and do some reading there...

 

Primary Metering Block:

Main Jet #51.2

Idle feed Restrictors #33

Power Valve #10.5

Power Valve Channel Restrictors #55

 

Secondary Metering Block:

Main Jet #60

Idle Feed Restrictors #55

Boost Regulated Power Valve #1.5 -------- I.E. I modified a #1.5 Holley power valve to work with boost pressure, GOOGLE BRPV!!!!

Boost Valve Channel Restrictors #77

 

Float Bowls:

single fuel feed float bowls with #130 viton needles and seats.

Nytrile floats

30 cc accel pump shot for both fuel bowls, remove the pump arm from the secondary accel pump diafram, I didnt need the double pump action.

 

Throttle Base Plate:

Install new throttle shaft bushings, dont be cheap, just do it!!!

Remove the secondary side accel pump cam and arm

Install the Blue accel pump cam on hole 1 for the primary accel pump shot

Install an adjustable secondary throttle shaft link arm and adjust to where the slack is just barely taught

Install a back fire protection check valve for the primary power valve, YOU NEED THIS!!

 

MY base plate is set up for 2 corner idle mixture adjustment. I tried the 4 corner idle base and it didnt work for me.

 

IF your confused, just google it....or go to theturboforums.com

 

Idle screw adjustment: 1 turn out from closed position on the primary side, CLOSE the secondary side completely or it can flood out your idle mixture.

 

This is my current running setup. Im at about 150-200 feet above sea level

 

You also need a boost refrenced rising rate ( 1 to 1 ) adjustable fuel pressure regulator, Low pressure-high volume, fuel return style. I use AEM

I use the stock Nissan fuel injection fuel pump for the 280Z, stock fuel lines. 50 micron Edelbrock fuel filter with replaceable filter element.

My idle fuel pressure is 6lbs.

 

TO NOTE: use caution during assembly of the metering block and fuel bowls to the main body. The gaskets can bunch up around the air flute holes at the top middle section of the metering block ON BOTH SIDES. IF you dont get this right you will push fuel out of this area and have a 400 HP FLAME THROWER!!!

[uberkevin]

PHOTOS!!!!!!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Nice how to.. it will help people.

[280zex]

I have many pix. I dont have a web host for the pix. screw photobucket. you can find my pix on the facebook ratsun page........

[280zex]

To note: depending on your altitude of where you live, you will need to increase the size of the secondary Idle Feed Restrictors. How much you ask??? I dunno, every car is different...