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Chevy 5.3 Liter LS Salvage - Generation Gap

Power And Performance From A 5.3-Liter LS? Yes, And Plenty Of It.

By Mike Harrington, Photography by Mike Harrington

Westech Tuner extraordinaire Ernie Mena is re-flashing the OE computer, with a tuning system from HP Tuners (more on that as well). Before the engine even started, the OE computer has to be re-flashed to remove the vehicle anti-theft codes and other codes that will hinder the tuning. It turned out we ran into some problems with the ECM. The engine was originally a fly-by-wire setup and the ECM that came from the Suburban was programmed as such. After re-flashing the computer with the new engine tune, the ECM still resisted. After several hours of tuning and re-tuning, we went out and got another ECM that was set up for a vehicle with a cable-actuated throttle. Once that was done, the new ECM took the tune and ran beautifully. Fortunately, a friend nearby had a cable throttle body 5.3 with the ECM sitting in the back of a parts truck. That saved a little over $200 from having to go to a dealership and buy one.

Once the engine was up and running properly, a pull was made using the factory tune. The engine pulled 344 hp at 5,000 rpm and 370 lb-ft of torque at 4,300. That's pretty impressive for a boneyard truck engine. Ernie Mena used the HP Tuners software and re-tuned the engine while it was running. After that, the ECM was flashed and another pull was made. This time the numbers were different: 357 hp at 5,400 rpm and 380 lb-ft at 4,300. Let's think about this for a moment: a salvaged 5.3 liter engine with a set of long tube headers, a harness and tuning software at the following price:

Ernie pulled the composite truck intake manifold off and set it to the side. Yes, the truck manifold is not as attractive as the lower profile LS1 intakes and does not work as well at the upper rpm range as the LS1 intake. On the same note, the truck intake creates more bottom end power than the LS1 intake. Replacing it would have added cost to the project.

While the engine was still on the dyno at Westech, we swapped cylinder heads and performed a cam swap. A set of higher-flowing Edelbrock RPM Xtreme cylinder heads and a Comp cam went in. When the valve covers are pulled off, we were very pleased with how clean the valvetrain was.

Speaking of facts, here are some numbers concerning the 5.3L LM7 engine.

5.3L Iron Block
Years
1999-2007
RPO #
LM7
Displacement
5.3 liters (325.2 ci)
Bore
3.780
Stroke
3.622
Compression
9.5:1

5.3L Aluminum Cylinder heads
Intake Ports
200cc
Exhaust Ports
70cc
Intake Valve
1.89
Exhaust Valve
1.55
Combustion Chamber
61cc

EDELBROCK 61949 CYLINDER
HEADS FLOW DATA
LIFT INT/EXH
.100” 64/57
.200" 134/107
.300” 193/147
.400" 239/180
.500” 274/200
.600" 285/210
By Mike Harrington
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