A 70hp increase for your 5.3L LS engine with Lift and Duration
Once again the LS engine proves big power can be had on the cheap
We hear the whiners all the time: "Everybody runs those stupid LS engines. They're boring!" We'll admit LS engines are less than visually inspiring, but there's a good reason these engines are so popular. Show us another engine that will deliver 70 horsepower with a simple cam swap! Keep looking we'll wait. Here's the push we started with a $350 Craigslist 5.3L iron truck engine. We added a mild Isky cam, valvesprings, and lifters and added 70 big ones. It was just too easy.
Our dyno victim started life as a 2002 LM7 5.3L engine (325 cubic-inch) and is among the most prevalent LS engines on the planet. GM has built millions of them. Factory specs for this engine with its truck's original EFI induction system is 285 hp and 325 lb-ft of torque, which is pretty good for essentially a small-bore (3.78 inch), long-stroke (3.62 inch) version of the traditional Chevy 327.
Because we were crunched for time, we didn't baseline our engine with an Edelbrock Performer RPM dual plane intake and 1-3/4-inch American Racing headers, but the guys at CLASSIS TRUCKS did with an identical 5.3L engine that made 315 hp and 325 lb-ft of torque. This is representative of that configuration, so we used these numbers for our baseline a solid 30hp gain over the stock production specs.
Because the cylinder heads on these LS engines produce much better flow numbers than those stock mid-'60s small-block Chevy heads, these late-model engines respond wonderfully to even a mild camshaft upgrade. We decided to give Isky a shot at the cam specs for our little 5.3L. Isky offers a raft of LS hydraulic roller cams in the catalog, so we chose one with 218/224 degrees of duration at 0.050 (see Cam Specs Chart).
Isky offers much bigger cams with more lift and duration, but we exercised restraint for several reasons. This is both a smaller displacement engine and is also intended for near-daily summertime street fun. We didn't want some Pro Stock-sounding staccato idle that would ruin the drivability, especially because we intend to pair this engine with an overdrive automatic and a lockup converter in an early '50s Chevy pickup. These parameters narrowed our selection to this midrange cam that offered shorter duration combined with a 113-degree lobe separation angle (LSA) compared to the stock cam's 116-degree angle.
LSA is an often-tossed about cam spec that can be somewhat confusing so it's worth closer inspection. The term refers to the number of cam degrees between the intake and exhaust lobe centerlines. The larger the LSA number, the more degrees between the lobes, which results in less valve overlap between exhaust valve closing and intake valve opening. All production LS cams use a very wide LSA to improve idle quality. Decreasing the overlap improves idle vacuum and contributes to a very smooth idle. If we add duration with the same LSA, this increases overlap. So our new cam does add overlap both with more duration on the intake and exhaust and also because the Isky cam's LSA is 3 degrees tighter, 113 versus 116 degrees.
We talked with Isky's Nolan Jamora, and he suggested we also test their new line of EZ-Roll hydraulic roller lifters fitted with bushings instead of the more common needle roller bearings. Isky was one of the first cam companies to address the issue of roller lifter needle bearing failures that seemed to especially plague big-block Chevys with mechanical roller cams and high spring pressures.
Isky's solution replaces the tiny roller bearings with a proprietary bushing material that radically increases the bearing surface area. Isky credits this lifter with what they call the Big-Foot Effect, where load distribution is increased by over 350 percent compared to needle bearings. Of greater import is the notion that the bushing virtually eliminates the classic roller lifter failure that scatters dozens of tiny needle bearings inside the engine where they usually cause terminal engine damage. It's worth noting that the preponderance of problems with roller lifter failures has been with mechanical roller lifters and less so with their hydraulic cousins. We asked Jamora about durability of the softer bushing material, and he said that with proper maintenance and oil changes that the company contends the lifter can easily go 100,000 miles.
Along with the EZ-Roll hydraulic roller bushing lifters is a matching set of beehive Isky valve springs, retainers, locks, seat inserts, and a custom set of 0.080-inch wall thickness pushrods. The pushrod length for our engine ended up being 7.500-inch long to compensate for the height of the Isky lifters. Given the net lash design of the LS engine, a different height pushrod seat in the lifter demands a change in pushrod length to retain the proper lifter preload. These pushrods were 0.100-inch longer than stock.
Swapping parts was not difficult, but because we were going to change lifters, this is one place where LS engine heads have to be removed where the small-block Chevy does not. Normally, if all we were going to do was swap the cam in this LS engine and reuse the factory lifters, this would be a snap. All you do is remove the pushrods and then roll the engine a couple of revolutions. The cam will push the lifters up into the guides and hold the lifters up off the cam so that the cam can be easily removed.
Because we were using the Isky lifters with built-in retainer bars, we removed the plastic lifter guides, and once the cam was installed, the new lifters dropped right in place. We also degreed the cam and then buttoned the engine up with an Edelbrock Performer RPM intake and topped it off with a Holley 750-cfm HP carburetor. With all that done, we were ready for testing.
With the engine bolted up on the SuperFlow dyno at Westech, we used a set of 1-7/8-inch American Racing headers without mufflers for this quickie test. Once we fired up our engine using the Edelbrock/MSD timing module to control the spark, we did some quick tuning on the carburetor and fiddled with the timing. All this took less than an hour to come up with a peak horsepower of 385 at 6,100 and 398 lb-ft torque at 3,900 rpm. This represents a dramatic 70-hp improvement over the stock cam. Even better, the factory 5.3L motor makes peak torque at 4,400 but with the Edelbrock dual plane, headers, and a bigger cam, peak torque happened at 3,900 rpm! This broadened the rpm spread between peak torque at 3,900 and peak horsepower at 6,100 to an amazing 2,200 rpm. Most engines generate a much narrower range of around 1,500 rpm. So for the street, this is a great combination.
In the final tally, we now have a smart little 5.3L street motor making nearly 400 hp that idles at 13 inches of manifold vacuum, and with a little bit of part-throttle carb tuning, our modern-day 327 could conceivably deliver decent fuel mileage, assuming you can keep your foot out the throttle! That sounds like a very successful street engine and all with a simple cam swap. SRM
|Camshaft||Adv. Duration||Dur. at 0.050||Valve Lift||LSA|
|Stock LM7 Intake||N/A||190||0.466||116|
|Stock LM7 Exh||N/A||191||0.457||---|
|Isky hyd. roller camshaft||271265-275||Isky||Call|
|Isky HPx EZ-Roll bushing lifters||2078-HYRT||Isky||$1,155.00|
|Isky valvesprings, beehive||165-A||Summit Racing||$211.97|
|Isky retainers, beehive||135-ST||Summit Racing||$101.97|
|Isky valve locks||VL-500||Isky||$86.00|
|Isky valvespring locators||255VSL||Summit Racing||$81.97|
|Isky pushrods||Call||Summit Racing||$179.97|
|Cloyes adjustable three-bolt timing set||9-3158A||Summit Racing||$149.08|
|Fel-Pro MLS head gasket for 5.3L (2)||26192PT||Summit Racing||$48.97|
|Fel-Pro intake gasket||1312-1||Summit Racing||$19.97|
|Edelbrock Performer RPM dual plane||71187||Summit Racing||$316.84|
|Edelbrock RPM and ignition module||7118||Summit Racing||$857.04|
|Holley 750-cfm HP carburetor||0-82751||Summit Racing||$560.95|
|American Racing Headers||Call||Am. Racing||$1,025.00|
|Holley LS oil pan||302-1||Summit Racing||$379.95|
|AMSOIL INC. Extended Life 5W-30, (6 qts)||XLFQT||AMSOIL||$8.60 ea.|
|AMSOIL INC. oil filter||EA15K50||AMSOIL||$17.50|
American Racing Headers
Holley Performance Products
Iskenderian Racing Cams