04SilveradoMykk
Full Access Member
Hey Guys,
I know this isn't a tech write up that will be used in day to day life, but more to answer that question 'How?' and resolve any general curiosity.
How to Install a Carbed Small Block Chevy in a GMT800, focusing on a 4.3L to SBC swap.
The SBC is a piece I built in a machine shop:
86-95 four bolt roller cam block, bored .040" over
906 Vortec heads, modified
LT4 Hotcam
1.6 ratio roller rockers
.525"/.525" 218/224 dur @ .050"
Comp 26918 beehive springs & hardened pushrods
Balanced ZZ4 rotating assembly
H345NCP-40 pistons
10-1 compression
Old 4.3L engine removed:
Transfer the 4.3L accessory brackets & pulleys over to the SBC v8, with some modification to clearance the tall valve covers.
As you can see, the SBC was originally fuel injected using 96+ L31 injection with the upgraded fuel injection spider. The K&N intake, 75mm throttlebody and several other little performance add ons were all transfered over from the 4.3L V6
Grafting over the fuel injection plug in
Re-pinning the PCM to the V8 firing ordered and adding wiring for two more injectors
Adding the custom made 3200rpm stall converter. Since I'm using a '04 4L60E with a early model engine block. There were several changes made between the two, one being the bell housing on the trans, it's more shallow on the late model than what had been used on the early stuff. Instead of adapter plates, I opted to have that slack taken out with a stall converter.
OE converter on left, my swap converter on the right
Adapting motor mounts, I decided to use a LSx to SBC adapter plate intended to drop in a LS1 into and older muscle car body. I used the same plate, but it's theory in reverse.
Since my truck is a v6 to v8 swap, not only did I need the 4.8/5.3 motor mounts, I also need the motor mount to frame brackets from a V8 as well.
Droping in the V8:
So there she is; a L31 fed, high compression, big cam, high stall, small block chevy in my 2004 Silverado. At this point in the swap I'm thinking " What have I done..."
I took the truck down to my shop to make the new exhaust for it, as well as spend time to write the new computer tune.
I spent weeks playing with computers and tunes, the trucks original PCM just couldn't physically be adapted to this generation of V8. Instead I used a 0411 PCM from an 02 express van, that PCM could control the drivetrain fine but it couldn't communicate with the rest of the GMT800 platform, my gauges were screwy, I lost A/C controls, I lost the oil pressure gauge, I even had to re-wire the ignition circuit... but it was running and I could drive it.
So I drove the truck daily to get to work & back, around town, etc.
I drove it for three months, the fuel injection just couldn't keep up with the demands of the motor. It had split BLM's, the PCM wasn't responding to O2's, and once that issue was fixed the PCM was commanding 100% injector PWM by 4000rpm. It had lack of power and was drinking 10- MPG
Instead of throwing more $$$ into a different kind of fuel injection, marine intake or otherwise, I decided to make yet another bold move. Install a Carburetor. An ol' tested & true, inaccurate, out dated and primal means of fuel delivery. But as inefficient as the ol' carb is, it sure can deliver big power easily... at the cost of fuel consumption.
I know this isn't a tech write up that will be used in day to day life, but more to answer that question 'How?' and resolve any general curiosity.
How to Install a Carbed Small Block Chevy in a GMT800, focusing on a 4.3L to SBC swap.
The SBC is a piece I built in a machine shop:
86-95 four bolt roller cam block, bored .040" over
906 Vortec heads, modified
LT4 Hotcam
1.6 ratio roller rockers
.525"/.525" 218/224 dur @ .050"
Comp 26918 beehive springs & hardened pushrods
Balanced ZZ4 rotating assembly
H345NCP-40 pistons
10-1 compression
Old 4.3L engine removed:
Transfer the 4.3L accessory brackets & pulleys over to the SBC v8, with some modification to clearance the tall valve covers.
As you can see, the SBC was originally fuel injected using 96+ L31 injection with the upgraded fuel injection spider. The K&N intake, 75mm throttlebody and several other little performance add ons were all transfered over from the 4.3L V6
Grafting over the fuel injection plug in
Re-pinning the PCM to the V8 firing ordered and adding wiring for two more injectors
Adding the custom made 3200rpm stall converter. Since I'm using a '04 4L60E with a early model engine block. There were several changes made between the two, one being the bell housing on the trans, it's more shallow on the late model than what had been used on the early stuff. Instead of adapter plates, I opted to have that slack taken out with a stall converter.
OE converter on left, my swap converter on the right
Adapting motor mounts, I decided to use a LSx to SBC adapter plate intended to drop in a LS1 into and older muscle car body. I used the same plate, but it's theory in reverse.
Since my truck is a v6 to v8 swap, not only did I need the 4.8/5.3 motor mounts, I also need the motor mount to frame brackets from a V8 as well.
Droping in the V8:
So there she is; a L31 fed, high compression, big cam, high stall, small block chevy in my 2004 Silverado. At this point in the swap I'm thinking " What have I done..."
I took the truck down to my shop to make the new exhaust for it, as well as spend time to write the new computer tune.
I spent weeks playing with computers and tunes, the trucks original PCM just couldn't physically be adapted to this generation of V8. Instead I used a 0411 PCM from an 02 express van, that PCM could control the drivetrain fine but it couldn't communicate with the rest of the GMT800 platform, my gauges were screwy, I lost A/C controls, I lost the oil pressure gauge, I even had to re-wire the ignition circuit... but it was running and I could drive it.
So I drove the truck daily to get to work & back, around town, etc.
I drove it for three months, the fuel injection just couldn't keep up with the demands of the motor. It had split BLM's, the PCM wasn't responding to O2's, and once that issue was fixed the PCM was commanding 100% injector PWM by 4000rpm. It had lack of power and was drinking 10- MPG
Instead of throwing more $$$ into a different kind of fuel injection, marine intake or otherwise, I decided to make yet another bold move. Install a Carburetor. An ol' tested & true, inaccurate, out dated and primal means of fuel delivery. But as inefficient as the ol' carb is, it sure can deliver big power easily... at the cost of fuel consumption.
