The Underdog Bites Back!
How to make 430 horsepower with a $200 4.8L engine.
Editor's Note: Yeah, technically this isn't a truck, but a Chevelle is just an El Camino without a bed, and an El Camino comes pretty close to qualifying gas a truck wannabe, right? Besides, where do you think the 4.8L came out of? Yup, a truck. Good engine tech is good engine tech, and if you don't know who Jeff Smith is, trust us, he's a source of good engine tech. So follow along as Jeff shows us all how to add some cheap horsepower to GM's most affordable LS variant.—Christian Hazel
Yeah, we know—why bother with a 4.8? It's not a 6.0L. Newsflash: Not everybody wants or needs a 6.0L LS engine. If that's true, then why a 4.8? It's only 293 ci. Our counter to that: Car Craft bought a complete LS engine including the accessory drive, intake, and coils for $200. We bolted in a cam, carbureted intake, and headers, and it made 383 hp (1.3 hp/ci). True, our little engine doesn't make as much torque as its heftier cousins. But a 4.8L delivers dirt-cheap LS power. When we pumped it up with a set of ported heads, we saw 432 hp, but we're getting ahead of the story.
The scenario looks like this. Your magazine-fed ego demands an LS7 or LS3 for your 1988 G-body [or truck!—ed.]. But reality quickly delivers that proverbial boot to the head when you realize your PBR beer budget can't even afford a hammered 6.0L, so most guys do nothing. Where's the fun in that? Here's where you have to get car craftier.
Find a cheap 4.8L and do the LS swap. Spend the important dollars on the intake, ignition, headers, and oil pan that complete the swap. If you have enough coin left over, you can add a small cam and valvesprings. All of these parts will bolt right on any LS engine as long as it has a 24x crank and cathedral-port heads. This gives you a head start on the project without spending big money up front. We've run across 4.8L long-blocks as cheap as $100. At this point, the engine is the cheapest item on the list!
Our example started in a familiar way. The engine we bought was advertised as a 5.3L back when we didn't know how to tell the difference. Our engine had flat-top pistons—a dead giveaway for a 4.8L. For the record, 5.3L engines use the same heads but come with dished pistons. A cheap bore scope from Harbor Freight is a good way to do in-cylinder identification. Borrow one from a plumber buddy—that's what we do! We decided to see just how well this little engine would run, so we bolted in a small Comp 219/223 hydraulic roller cam, retained the stock lifters, but added better springs. Then we bolted on an Edelbrock Performer RPM dual-plane, a Holley 750-hp carburetor, and the MSD ignition box to run the spark. The only other change was to a Champ LS engine swap oil pan to clear the crossmember.
You might recall that, with this engine in our Orange Peel Chevelle, it ran an 8.48 at 85 mph in the eighth-mile. Later we ran the car at Bakersfield, and its best was a 13.45 at 106 mph. The biggest disappointment was that with such a small engine, the 60-foot times were slow (2.02 being its best). But the trap speed of 106 mph was fun. We knew we could improve that e.t. with better gear, but even with an overdrive trans, we didn't want to put more gear in it than the current 3.55:1. Lastly, all these runs used a pair of Holley exhaust manifolds. A set of long-tube headers would have really helped the low-speed torque.
A series of "what-if" scenarios persuaded us to yank the 4.8L and stick it on the dyno. Remember, this is a 140,000-mile 4.8L truck engine with stock 9.5:1 pistons and heads. All we did was improve upon the camshaft and the induction. The only change we made on the dyno was to add a set of American Racing 1-3/4-inch headers. We wanted to test with the Holley exhaust manifolds, but our exhaust lead-down pipes wouldn't clear the dyno stand.
Our first pull on the mighty 4.8L produced a surprising 383 hp out of this littlest warrior. Next, we've heard lots of rumors about how much power a stock LS water pump demands at rpm, so we thought we'd find out. Bolting on a Meziere electric water pump, the results were somewhat surprising.
The electric water pump added an amazing 16 hp at 6,000 rpm and bumped the peak horsepower an additional 10 to 393 hp. If you study the graph, you can see that Meziere's pump improves the power throughout the entire run. Yes, part of this test did eliminate the alternator, as well. If we assume an output of 50 amps, the conversion is 0.8 hp. This Meziere pump only pulls 7 amps, so the added electrical load of not quite 2 hp would be inconsequential.
For our final test, we wanted to evaluate a set of mildly ported production heads from our pal, Richard Reyman, owner of West Coast Racing Cylinder Heads (WCRCH) in Van Nuys, California. If you send him your stock 4.8/5.3L head castings, he performs a simple CNC pocket-porting job along with installing larger 1.95/1.57-inch stainless steel valves all for just $1,062.
After porting, WCRCH outfitted our heads with a set of (extra-cost) Brian Tooley Racing (BTR) dual valvesprings and matching retainers, and we bolted the heads down with ARP head bolts and new Fel-Pro head gaskets. The only other change was to mill a few thousandths off the deck surface to reduce the chamber volume to 53cc. This was worth almost exactly 1 point in compression, bumping our 4.8L to 10.5:1 compression.
From the first pull on the dyno by our pal, Richard Holdener, we witnessed an instantaneous push in torque and horsepower. This wasn't just a gain at peak rpm. The head swap produced a 2.5 percent gain even at the bottom—likely due more to the compression ratio than airflow. At the top, the gains were far greater, producing an even 40 hp on this tiny dancer to create 432 hp at 7,000 rpm. Granted, that's a lot of rpm, but the engine repeated this several times with nary a complaint. To put this in perspective, 432 hp from 293 inches is 1.47 hp/ci. That's an outstanding number in anybody's book.
Car Craft will soon drop the engine back into the Orange Peel Chevelle. Since the power numbers were mainly realized at higher engine speeds, they may mean only minimal gains in e.t. We expect to see bigger increases in trap speed mostly because Orange Peel is heavy with a 3.55:1 gear and a tight converter. Our expectations are for the car to run low 13s at 108 mph. With a 4.10:1 gear, it would easily push into the high 12s. Not bad for a $200 junkyard refugee!
|Camshaft||Adv. Dur.||Dur. at 0.050||Valve Lift||LSA|
|Comp LS1 269Lr|
Ports O' Call
These are the WCRCH published flow curves for both the stock and ported versions. Stock valve sizes for the 4.8/5.3L heads are 1.89/1.55. The WCRCH heads use 1.95/1.57-inch stainless steel valves. All tests were performed on a 3.78-inch test bore using 28 inches of water test depression. The exhaust-to-intake percentage is a way to evaluate the relative performance of the ports. Anything above 70 percent is considered very good.
|Exh. to Intake %|
|0.100||65||56||69 (+4)||56 (+0)||72%|
|0.200||133||96||135 (+2)||100 (+4)||76%|
|0.300||188||133||194 (+6)||143 (+10)||74%|
|0.400||206||160||238 (+32)||177 (+17)||74%|
|0.500||218||172||265 (+47)||197 (+25)||74%|
|0.600||223||175||250 (+27)||206 (+31)||82%|
Test 1 was the 4.8L engine with the Edelbrock Performer RPM intake, Holley 750-cfm HP carb, American Racing headers, MSD ignition box, and the Comp hydraulic roller camshaft.
Test 2 exchanged the stock truck water pump for a Meziere electric pump.
Test 3 added a set of WCRCH stock castings that were lightly ported with larger valves and the same 26918 valvesprings. The numbers in the far right columns evaluate only the gains with the cylinder heads—the difference between tests 2 and 3.
As you can see from the graph, the combination of the heads and the electric water pump produced some serious gains with a peak horsepower of 432. What is even more amazing is that in all three tests, peak torque occurs at 4,000 rpm and peak power at or near 7,000—that's a powerband of 3,000 rpm, roughly twice that of most engines.
|Used 4.8L engine||NA||Craigslist||$200.00|
|Edelbrock Performer RPM intake||71187||Summit Racing||316.84|
|Holley 750-hp carburetor||0-82751||Summit Racing||560.95|
|American Racing headers, 1-3/4||Call||American||1,195.00|
|WCRCH 5.3L head (exchange)||5.3L||WCRCH||1,062.00|
|WCRCH 5.3L head (outright)||5.3L||WCRCH||1,312.00|
|MSD ignition controller||6010||Summit Racing||356.95|
|MSD spark-plug wires||32813||Summit Racing||72.37|
|Comp hydraulic roller cam||54-456-11||Summit Racing||373.97|
|Comp adjustable timing set||3158KT||Summit Racing||170.97|
|Comp valvespring set||26918||Summit Racing||180.97|
|Champ oil pan||LS1000||Champ Pans||267.59|
|Champ pan pickup||750LS1||Champ Pans||51.52|
|Champ oil-filter adapter||LS1001||Champ Pans||105.28|
|Fram oil filter, Tough Guard||TG3506||Summit Racing||7.97|
|Autolite spark plugs, 8||5245||Summit Racing||15.76|
|Fel-Pro head gasket||9292PT||Rock Auto||13.80 ea.|
|Fel-Pro intake gasket||13121||Summit Racing||19.97|
|ARP head bolts||134-3609||Summit Racing||199.97|
|ARP crank bolt||234-2503||Summit Racing||34.57|
|Lucas 5W-30 oil||10049||Summit Racing||7.97 ea.|
|Meziere electric water pump||WP119||Summit Racing||494.85|
|Harbor Freight inspection camera||61839||Harbor Freight||79.95|
Automotive Racing Products (ARP); 800/826-3045; ARP-bolts.com
American Racing Headers; 631/608-1986; AmericanRacingHeaders.com
Comp Cams; 800/999-0853; CompCams.com
Edelbrock (Russell); 310/781-2222; Edelbrock.com
Harbor Freight; 800/423-2567; HarborFreight.com
Holley Performance Products; 270/781-9741; Holley.com
Lucas Oil Products; 800/342-2512; LucasOil.com
Rock Auto; 866/762-5288; RockAuto.com
West Coast Racing Cylinder Heads; 818/705-5454; ProHeads.com