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So the project guideline was not to modify anything that cannot be returned to the Original L48 / Auto factory configuration. (except for the tunnel mod for the T56 magnum Shifter).
So everything needed to be mounting to existing mounting points and wires needed to be routed via existing firewall holes.
No wiring connectors where cut at all. Made adapters using the correct connectors from the factory 78 wire harness to required connector on the other end.
with the GM Controller / wire harness (19354330) including drive by wire gas pedal.
1982 fuel sending unit with a areomotive stealth 340 fuel pump. Custom hardline from the sending unit to a C5 fuel filter regulator mounted on the driver side frame rail next to the fuel tank. Then a hardline from the fuel regulator to a mid point on the driver side frame rail. Then a hardline from the mid point to the driver side engine frame rail. This may change next year with a properly baffled tank but for now it is working as excepted.
Made a custom gas pedal bracket mounting to the existing gas pedal mounting holes.
Wire routed via the hole from the gas pedal cable ( required to remove the pins from the connector and re-connect )
Accessory bracket was the holley 20-135, important note the accessory bracket alignment needs to match the crank damper on the engine. There is 3 possible dimensions , My engine uses the corvette / CTSV spacing which is the closest to the block. Did not reconnect the AC yet, but since the car is used for track days I am not sure I will reconnect.
Power steering GM type II pump below with a remote reservoir and the high mount alternator. This mounting bracket is also the same as my C6 2010 Grandsport including power steering pump and alternator. But find a non corvette part # to save money.
Now the power steering Pump required a smaller dia pulley to clear the driver side control arm. Also the control arm bolt needed to be reversed for additional clearance.
All shims were removed and alignment was adjusted via the upper control arm shafts ( spc upper arms ) This was already on the car.
Motor Mounts where from ICT 551128-301 which places the LS3 near factory SBC engine, ~ 1/2" forward.
With the SPC Upper arms I was able to connect the heater hoses without mods to the water pump.
Radiator is a dewitts aluminum rad for the factory 1978 c3 corvette. Hoses were cut from a factory hose. Needed 2 x 90 degree bends for both upper and lower rad hose.
Started as this
exhaust manifold was from a LS7 crate motor including heat shields plus addition mounting points for other heat shields
No clearance problems with anything. Only exhaust bolt that requires a s shaped wrench is the rear driver side.
Wiring was the easy part.
1. Connect to battery 2. Connect to 12v ignition 3. ground. 4. connect pump controller to pump 12 V 5. connect fan control to 12v fan relay. ( part of the dewitts alum rad with spal fans )
Routed the ODB2 connected via a hole on the passenger side firewall mounted under the glove box
6. Installed temp sensor at the passenger side rear of block to connect to the factory temp gauge. Need to use variable resistor to calibrate to 200 degree F. 7. Alternator L wire made connector to plug into the factory wire harness ( alternator light ) 8. drilled and tapped 1/8 NPT into the oil cooler ls3 plug by the oil filer to connect the factory oil pressure gauge. Or you can buy a plug with the connector already to go. 9 re-program the ecu to output the factory 8 cylinder tach signal (gm programed as 4 cylinder) Customer wire connector to plug into the factory tach connector. (5k pull up resistor required)
All vacuum hoses connected to factory type locations, plugged the cruse control vacuum line, PCV Valve line.
LS3 PVC system used factory GM Parts from my C6 2010 Grandsport.
Air system used off the shelf parts custom sized to fit.
I have left out some details but the worst part was installing new fuel hardlines, and determining the accessory system that will fit. Many LS3 swap vendors make claims as to what fits BUT IT DEPENDS ON THE CRANK DAMPNER POSITION.
So as for performance waiting to take it out to the track, but pulls much harder than the ZZ383.
As for gas mileage my ZZ383 got 27.4 mpg
and the LS3 I got a great 33.1 mpg
Last edited by cagotzmann; Nov 26, 2023 at 01:55 AM.
Looks fantastic and I bet it runs great. What specific part did you use on the water temp gauge to get accurate readings? I need to do this mine too. Thx!
Looks fantastic and I bet it runs great. What specific part did you use on the water temp gauge to get accurate readings? I need to do this mine too. Thx!
Its not accurate except for near 200 degree F
Based on this scale. Added my custom resistance based on what my gauge resistance required to the 200 Degree mark.
Thanks for the info. I don’t have an hptuner but was thinking of getting a data logger so I can see what the ECU is reading. Currently using a 98 camaro 3 wire sensor and factory temp gauge.
I'm glad you had great success with your LS swap.
One of the coolest things about a properly wired, plumbed and programmed LS swap is how fast it will fire when you turn the key for the first time. It's kind of scary if you haven't done one before.
I'm glad you had great success with your LS swap.
One of the coolest things about a properly wired, plumbed and programmed LS swap is how fast it will fire when you turn the key for the first time. It's kind of scary if you haven't done one before.
Yes on the first startup I could hear the pump fill up the rails seen 60 PSI
cranked to start
And a huge loud noise. ( straight pipes only on first startup , ha ha ) , but compared to my ZZ383 which took a lot more cranking / tuning / setup just to get it to start.
All EFI systems first startup is must simpler.
Before first startup I checked FUEL PSI & my computer could read the ECM, throttle position sensor detected gas pedal changes. No MIL errors so then proceeded to cranking for start.
both are using the same HP rating method from GM. which is 425 vs 495.
Speed during MPH was ~ 65-68 MPH and yes MPH is based on imperial gallon.
I’ve seen dyno videos where the engine HP numbers for the sbc style crate motors are
in line with what GM rates them at, but under the same test conditions, the LS crate
motors dyno significantly higher. Base Ls3 motors engine dyno about 500hp
Pretty impressive mpg at 105-110 km/hr. Was that on the QE2 or one of the
main roads around Edmonton?
I’ve seen dyno videos where the engine HP numbers for the sbc style crate motors are
in line with what GM rates them at, but under the same test conditions, the LS crate
motors dyno significantly higher. Base Ls3 motors engine dyno about 500hp
Pretty impressive mpg at 105-110 km/hr. Was that on the QE2 or one of the
main roads around Edmonton?
1978 LS3 Swap Completed.
