In the 11 years since the LS-series of small-block Chevys was introduced, they have been factory-installed in everything from Corvettes to passenger cars, trucks and SUVs. It's the latter that we want to focus our attention on in this article.
Among the advantages of these engines are factory aluminum heads, lightweight composite intakes and in some cases aluminum blocks. Many, such as the 5.3L (RPO LM7) have a cast-iron block with aluminum heads and composite intake. While the LS1 has received tons of attention, the 5.3L V-8 is of a lesser-known quantity. Literally millions of these cast-iron 5.3s have seen service in vehicles like Suburbans and Silverados.
Take a walk through any salvage yard and you're bound to come across plenty that have met an untimely end. We recently did just that, visiting Dave's Golden West Auto Wrecking in Westminster, California, where we found tons of wrecked late-model Chevrolets with 5.3-liter engines.
For all practical purposes, the Gen III 5.3 is nearly equal to its older brother, the 5.7 LS1. In fact, the iron-block 5.3 can be bored out to 5.7, and any performance mod done to an LS1 can be done to the smaller 5.3. But that's not the purpose of this article. The goal here is to take a salvaged engine that is in good shape and add a few items to open up its nostrils so it can breath a bit easier. We were curious to see what kind of power it would make in stock trim and then with aftermarket goodies-in this instance, heads and a cam.
Most of us will never stop driving our beautiful classic cars, regardless of the price of fuel, and the modern 5.3 presents an excellent way to consume less gasoline and have excellent power for our classic rides. This particular engine will end up between the rails of a '58 Chevrolet Apache Fleetside truck.
Westech manager Steve Brule is setting up the Painless harness system we employed (more on that in a moment) and plug wires. The 5.3 came with the entire factory accessory drive system, OE harness and electronic control module (computer). The accessory drive system was removed and a Meziere electric water pump was installed. A set of long tube dyno headers carried away the exhaust. Other than that, this engine is stock.
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
Displacement5.3 liters (325.2 ci)
5.3L Aluminum Cylinder heads
When the OE heads were pulled, we got another pleasant surprise. The cylinder walls were smooth, clean, and unscarred, and the pistons had very little carbon build up on them.
The deck surface of the block was scraped clean, wiped down and was ready for the new Edelbrock cylinder heads.
While the stock 5.3L cylinder heads can do a decent job, to really wake up the 5.3, we went with Edelbrock Performer RPM Xtreme LS-series heads. The RPM Xtreme cylinder heads (PN 61949) are cast aluminum and CNC-machined in all the critical areas-combustion chambers, intake and exhaust runners, and intake and exhaust bowls. At $2,073, this combination makes them more affordable than a set of fully re-worked stock heads. These cylinder heads feature 65cc combustion chambers, 214cc intake runners and 80cc exhaust runners. The intake valve size is 2.02-inch and the exhaust valve is 1.57. They also come with a 5/8-inch deck surface should you decide to machine them for additional compression. Compare these numbers to the numbers of the stock heads. Bigger valves plus bigger runners equals better breathing.
For a cost of $3,073.85, we had a stout cruising engine with 357 hp and 380 lb-ft of torque that gets great mileage. At this price, what's not to love? But this wouldn't be Super Chevy magazine if we left well enough alone, so we're going to perform a few more installs and bump up the power.
While Steve cleaned the deck surface, Ernie installed the Comp Cams Xtreme RPM roller cam (PN 54-416-11). We included a shot of the cam card for your viewing pleasure. The cam's effective range is from 1,660 rpm to 6,600 rpm; intake duration at .050 is 220 degrees, exhaust duration at .050 measures 224 degrees with a 112-degree lobe separation. Using the factory rocker arm ratio, the intake valve lift is 0.530-inch and the exhaust is 0.534-inch.
The factory torque-to-yield bolts are not reusable; Edelbrock suggests using ARP head bolt kit (PN 134-3609).
One thing to note before putting on the cylinder heads: Use the correct head gasket. In the Fel-Pro line, there are two different types of gaskets for these engines. One is for the 5.3L and one is for the 5.7L. The 5.3L head gaskets will not work with these newer Edelbrock heads; the 5.7L LS1 head gaskets are the correct ones to use due to the increased combustion chamber size.
Salvaged Engine $800HP Tuners $649
Edelbrock Cylinder Heads $2,073ARP bolts $149
Summit 80mm Throttle Body. $269.95Painless Wiring system $589.95
Comp Cam $399.95Hooker Headers $704.95
Total $5,635.08prices taken from the Summit Website.
Checking pushrod length is simple if you happen to have one of these tools from Comp Cams. Each tool comes in a specified rod length range and each complete turn is equal to .050 of an inch. It is imperative to measure for the correct pushrod length with a cylinder head swap.
Here's the proof. The dotted line represents the power and torque band prior to the head and cam swap. The solid line represents the new power and torque after the swap. The power and torque curve is not only a beautiful thing to see, but the peak horsepower numbers are beyond impressive when compared to the stock numbers. The horsepower peaked at 441 at 6,200 rpm, while the torque peaked at 410 lb-ft at 4,800 rpm. That's a 97hp gain over the initial stock numbers and a 40 lb-ft improvement over the initial pull. The '58 Chevy truck where this engine will end up will cruise down the highway with decent power and get decent mileage all at once. That's having your cake and eating it too.
If the OE computer is the brain of the engine, then the wiring harness is the spinal cord. The spinal cord that was used in this engine build was the Painless Performance fuel-injection harness (PN 60218). This particular factory-style harness is designed to work with the stock ECM and plug into all the sensors and controllers that are vital for the engine's function. Not just any stock ECM will work; check the serial number on the back of the Delphi ECM to find out if it is compatible with this harness. For more specifics, call Painless Performance's tech line, or check its Web site for compatibility. During the tuning phase, we did encounter one problem. The ECM that came with this engine would not take a tune and function properly.
Originally the ECM and engine was set up from the factory to work with a fly-by-wire throttle body. We changed the throttle body to a cable control. Either the fly by wire ECM would not co-operate with a harness designed for a cable set up or the ECM was just plain bad. Once we switched out, the fly-by-wire ECM and used a cable ECM it took a tune and worked beautifully. As an added bonus, if you do purchase the Painless harness for the LS-based engine, Painless will re-flash the factory ECM for you, removing things like the vehicle anti-theft and other problems, and it will be guaranteed to work with their harness. That free service alone is worth hundreds of dollars or hours of trying to figure it out on your own like we did.
The attractive truck intake is bolted back on and the rest of the engine is wired up again and ready to test. Side note: The stock pushrods were about to be re-used, however Steve was wary about the excessive amount of pre-load that was put onto the lifters. A shorter pushrod (7.325-inches long) was used and the results were much better.
Back in the dyno room control center, Steve mans the power while Ernie re-tunes the engine on the fly and re-flashes the computer. After a few pulls and re-maps of the tune, they found the sweet spot and made a final pull.
Forget the torque to yield bolts, They're only good for one go around. Spend the couple of extra bucks for a recommended set of ARP bolts.
Comp Cams recommends the right springs for its cams. Fortunately, the Edelbrock springs were sufficient to handle the lift of the Comp Cam. Suffice it to say, the 220/224 Comp cam extended the rpm range and the oh-so important power curve.
We ditched the stock 78mm fly-by-wire throttle body and instead used a Summit cable-controlled cast-aluminum 80 mm throttle body (PN 227725).
Last and certainly not least, is the HP Tuners software and hardware. If the engine can't be custom tuned, squeezing out some extra power is impossible, making the ability to tune and re-flash the computer essential. HP Tuners offers two MPVI interfaces-the Standard, and the Professional. The pricing is $499 for the MPVI Standard Interface or $649 for the MPVI Professional. We used the professional model since it offers the most, and the technicians at Westech already have it on their computers. HP Tuners does do not provide a specific tune, rather the ability to tune is what the system is about. HP Tuners supplies access to a repository of base tunes as a starting point. The HP Tuners Web site also has several demo tutorials and even a forum filled with information on how to tune various GM vehicles. We highly suggest you browse the site to learn more about tuning.