cagotzmann

So I completed the LS3 swap in my 1978 corvette.

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.

So the swap was from the GM ZZ383 to the LS3.

So the basic install notes are the following.

Engine is a GM Crate LS3 / 480 engine (19419864) LS376/480 495HP Hot Cammed LS3 - 4 LEFT AT OLD PRICE !!: GM Performance Motor

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

doorgunner

CONGRATS! I am jealous on several levels

sci85

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!

cagotzmann

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.

auto meter part 2258/2259

ºC ºF Ohms
38 100 1123
49 120 708
60 140 460
66 150 374
77 170 253
88 190 175
99 210 123
100 212 119
104 220 105
110 230 89
121 250 65
138 280 42
149 300 32
160 320 25
171 340 20

I would first connect as is, use the ECU to read the actual temp and check where the needle is when you get to 200 degree F, it might be close.

Wilcox Corvette makes a unit for factory SBC sensors which will work with this application as well.

sci85

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.

carriljc

cagotzmann
Do you have a picture of this? I am more curious than anything else since folks seem to struggle dealing with the heater hoses on LS swaps.

cagotzmann

Here is the pictures I have.

Tranz Zam

Looks awesome!

I'm sure it gave that Vette a serious kick in the *** too!

71 Vert LS1

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.

cagotzmann

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.

cagotzmann

Well the ZZ383 was rated for 425 hp so going to 480 hp wasn't a big change.

But being EFI the throttle response is much better ?

Also going from 27.4 MPG to 33 MPG also helps.

455230

Probably a lot more than 55 hp difference. Zz383 is gross hp, LS is net.

Im assuming imperial mpg .

What speed did you do the mpg at?

Is that still with the 3.08 rr gears?



What speed was the mpg taken at?

BTW, excellent work!

cagotzmann

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.

455230

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?

Is Castrol raceway still open?

Fly skids up!

Very nice!

cagotzmann

Castrol is still open. Drag & road course.

Anthony Henday Dr. Loop same as my ZZ383 test.

cagotzmann

Did some similar acceleration runs.
2nd gear

47km - 125km (2000-5400 RPM)

ZZ383 average ~ 5.9 sec.
LS3 average ~ 5.4 sec.

So confirmed it pulls harder as excepted.

455230

Does it pull a lot harder from 5000 rpm and up vs the 383?

cagotzmann

Pulls harder at all RPMS, But @ 5000 rpm its hard to tell without a device for measuring response.

Only test I have done is 2000 RPM - 5400 RPM run.

ZZ383 average ~ 5.9 sec LS3 average ~ 5.4 sec.

djquik1

Very nice set up. Makes me want to do a LS swap and build the Lq9 I have on the stand instead of my Gen 1 based on your fuel economy alone