Carb Swap

[04SilveradoMykk]

Well guys, here it is.

After helping a dude drop a carbed 383ci SBC into his NBS 2004 Silverado.

I decided to ditch my L31 fuel injection in favor of an old school carb & manifold on my SBC sitting in my NBS that I droped in last Sept.

There were several reasons for making this decision.

First & formost. Because I want to...

2nd) The PCM & fuel injection have been giving me nothing but headaches since the swap. 6-8 MPG average while delivering less power to the ground than the stock 6 cyl. Stuck in open loop, not responding to tuning, I just said "ah to hell with it..."

3rd) The 0411 PCM required to operate the L31/4L60e is not 100% compatible with the GMT800 platform. I lost the use & function of my...

Air Conditioning
Oil pressure gauge
Shift/gear indicator in the cluster
Reverse Lights
As well as unleash flashing error messages in the message center for sensors my truck didn't even have.
Check oil level
Check coolant level

4th) Have you ever seen a old school hot rod SBC in a NBS? Yea, me neither.

Look, the F.I unit even looks like a snail





Professional Products 52028 manifold. A copy of the edelbrock RPM Air-Gap



Summit distributor. Since the PCM doesn't need the cam sensor to determan RPM



The carb: Edelbrock 1407 750cfm, jetted & rodded 4% lean for altitude. Converted to electric choke



Modified the shaft of the primaries to fit a TPS sensor





The carb is sitting backwards on the manifold to make easy hook up to throttle cables & TPS sensor harness. As well as having the vacuum lines on the back made for easy PCM valve & vacuum advance hook up.

Modified the carb vacuum port & NOS fogger to inject nitrous & fuel into the secondaries. Jetted for 100hp shot



I don't like those edelbrock foam air cleaners. But as you can see, space is an issue and it fits.



The previously used coil now mounted on the valve cover



The trucks original throttle cable. Fit perfect into this cheap generic chrome bracket



Put back together, Mallory 4309 fuel pressure regulator with a return.



I've got a few litle odds & ends to wrap up; Pipe plugs, bolts & shorter ignition wires. Those Taylor wires are too friggin long!

With the L31 F.I. out of the way I am going to put the trucks original 6243 PCM back in place and tune out every single engine/fuel DTC.

With the trucks original crank sensor, TPS, VSS, ECT and oil pressure sensors the PCM will be able to control the 4L60E trans and the factory gauge cluster.

For you die hard F.I. guys out there, tough. With a 750 carb & Air-Gap manifold this engine makes 401hp/426tq on the dyno. The F.I. just could not deliver.

And, now this engine compartment will get a double take " Huh.. a carb?!"

Cheers ~Mykk

[Chevyman247]

I knew this would happen.

Video?? I wanna hear this beast.
One day I need to get around to putting a roller cam in mine, my stock block is allready drilled and tapped from the factory for the spider.

[SimpleGreen]

Very cool Mykk. Im always game to see somebody go 'backwards'

What was the reasoning for picking an Edelbrock? Just curious. Ive never had one. I know I have a friend that hates them. I bought my Holley just because all of us around here had more experience with them.

[04SilveradoMykk]

I prefer edelbrock carbs... I've owned Holleys, and all of them were leaking POS's

I once built a 454ci, tunnel ram manifold. Dual edelbrock 500's and I've been hooked on them ever since.

[SimpleGreen]

I prefer edelbrock carbs... I've owned Holleys, and all of them were leaking POS's

I once built a 454ci, tunnel ram manifold. Dual edelbrock 500's and I've been hooked on them ever since.

Thats cool. My Holley before this one was a leaky POS, so I had my friend swap it for another while he worked at Autozone. Ever since its been on my 350 though its ran like a champ.

[WetPaintSierra]

You gonna post new exhaust/driving vids when done?

[04SilveradoMykk]

You gonna post new exhaust/driving vids when done?

Of course, I couldn't imagine the exhaust note being much different except it might not be as Sharp as it previously was.

[04SilveradoMykk]

Spare Parts

[k20chevy 454]

wheres that k&n element going,that would be nice for my 79

[04SilveradoMykk]

99.9% done.

Made a upper coolant hose to work, finished wiring the ignition as well as shortened the spark plug wires, put in new NGK TR55's, Filled it back up with green coolant.

The only thing left to do is get a fitting; 3/8" pipe 90* to a 5/16" hose barb for the fuel return line. Than I can check for any fuel leaks, and make sure the fuel pressure regulator is doing what it is supposed to.



Than to test fire, set the timing, adjust idle, tune the carb and take her for a test drive.

Cheers ~Mykk

[04SilveradoMykk]

It's alive. Still needs tuning, of a none PCM nature :P

http://www.youtube.com/watch?v=IwfN_-xU40Q

There is still one issue that's currently getting resolved. The fuel return line is to small to successfully regulate the 60PSI down to 6PSI and the return line is getting backed up and causing too much pressure at the carb.

Plan: Drop the tank, remove the in tank pump and run a generic electric pump on the frame rail. The pump I found runs 72GPH @ 5.75PSI. And I should have the second part of this swap finished in a couple days.

Cheers,
Mykk

[04SilveradoMykk]

Today I tackled the thank & F.P.



Replaced the in-tank pump with a piece of straight line



using the soldering gun to cut away the plastic to tighten the hose clamps



welded the fuel pump bracket to the cross-support



tomorrow I'll tap into the existing FP power lines and put the tank back up.

[04SilveradoMykk]

I've been driving the truck since last thursday. No problems, it has alot more of everything. Better torque, much better power, better gas milage, better exhaust tone & a more controlled "cammed" idle

http://vimeo.com/3125480

I didn't notice the black rich smoke until I was filming, I've since stepped the accelerator pump down a notch and it cleared it up

I put my 6243 PCM back in place and it's nice to have my oil pressure gauge and shift indicator back as well as getting rid of erroneous messages in the gauge cluster. I've yet to turn off DTC's via HPTuners, but the trans still shifts just fine

Cheers ~Mykk

[98GreenMachine]

Looks cool man

I know you will attract alot of negative carb-related attention, but hey, its what you want and its working out better than the L31 FI was so more power to ya