A couple of decades ago, you could easily pick the boneyard for an inexpensive engine core that would polish up nicely with a little cleaning and some machine work. Chrysler made millions of big-block wedges and LA-series small-blocks, and by the 1980s, they were strewn on the ground like rocks. Those days are gone, and those "rocks" (at least the ones worth having) have turned into gold nuggets—with a price to match.

On the positive side, technology has marched forward, and the vintage V-8 cores of the 1960s and '70s have been replaced in those same scrapyards by 318- (5.2L) and 360ci (5.9L) Magnum small-blocks from the 1990s. These were used in everything from Ram trucks, to Dodge Dakotas and Durangos. Since they were based on the previous LA series of small-blocks, they easily fit between the fenders of our favorite vintage Mopar machines, making them the perfect candidate for a performance street build-up.

See all 52 photos Fred Hafliger of IMM Engines in Indio, California, handled our build. IMM's specialty is high-performance Mopar.

Isn't the Mopar 360 "Magnum" a Big-Block?

Newbies just getting into the Mopar hot rodding game always ask us if the Magnum is a big-block. After all, the name Magnum graced some of the most potent Chrysler big-blocks of the 1960s. In a bit of a PR move, Chrysler named its redesigned small-block the Magnum when it came out in the 1990s, thus throwing the monkey wrench of confusion into the works for anybody just getting started. Rest assured, the Magnum we're talking about here is indeed a small-block, which factors into its excellent affordability and availability.

How Much HP Can a Magnum Take?

As we'll get into later, the Magnum came in two flavors: the 5.2L and the 5.9L. Both had cast pistons and crankshaft, making them the weak link. The blocks, however, have proven to handle a lot of abuse when stuffed with the proper components, namely forged pistons, as we'll perform here in this rebuild. To that end, we'll jump to the end and say we made an easy 455 hp on pump gas using the stock block and factory rods. This power number is limited the most by the cylinder head flow, manifolding, and valve timing, but those factors are a cost limitation, not a strength issue. The short-block as built here could handle significantly more if needed (proper ring gap aside), and 600 hp would certainly be a safe number for this short-block.

See all 52 photos We found a 5.9L Magnum from a late-model truck at AAMidwest for $250. Compared to early-model LA-Series cores, late-model Magnums have less bore wear and bearing damage due to EFI. This limits cold-start fuel wash and detonation.

While you might frown that the Magnum isn't the basis for a Concours-correct, numbers-matching mill, you'll be happy to know that a good Magnum core can be had from most any local junkyard for under $500. By "good," we mean the block and rotating assembly is serviceable with a few basic clean-up and refurbishing operations. Moreover, because these Magnum engines were all EFI, they don't suffer from the debilitating bore wear and bearing abuse of their vintage carbureted counterparts. Modern engine management was designed to prolong engine life and reduce cold-start wear from fuel wash, not to mention counteract damaging detonation from low-octane fuel. This means these cores are more often than not in great condition, even with over 100,000 miles showing on the clock.

See all 52 photos Since 318ci (5.2L) and 360ci (5.9L) cores look almost identical, you'll want to look for the casting number in the block. This 5.9L core is cast with the numbers "360" on its side.

These engines first appeared in 1992 (5.2L only, the 5.9L in 1993) and were made by the millions through the 2003 model year. The 360ci (5.9L) Magnum had a rated output between 230 and 250 hp. Nevertheless, engineers underestimated its role as a hard-working truck engine, and its thin-deck cylinder heads often had problems with cracking and warping—especially when run on low-octane fuel. This is actually a good thing for us, because not only did that prematurely inflate the supply of good short-blocks, it also brought good aftermarket cylinder heads into play to good effect.

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Best Magnum Replacement Cylinder Heads

One of those cylinder heads is the EngineQuest CH318A, a cast-iron replacement head designed ostensibly for the OE replacement/rebuilders market but also conceived as a mild street performance part that, with modest effort, can be modified to produce significant gains in flow. The EngineQuest CH318B casting was designed to be used on a Magnum block, but it has the LA series intake bolt pattern, so it can take any of the wonderful high-performance LA intakes (318/340/360) on the market. This increases the horsepower and keeps a cap on the cost.

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When IMM modifies the EQ heads, they open the valve pocket area, blend it into the throat, put a nice valve job on it, and put larger 2.02-inch intake valves in them. At $1,469 for a pair, it's easily the most expensive part of this build-up, but good heads are essential for making power. For those curious about using them with a Magnum intake, you'll be glad to know EngineQuest also offers the CH318A—an identical casting that retains the Magnum intake bolt pattern.

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Magnum Induction & Camshaft

Pairing your cylinder heads with an intake manifold that's appropriate for the flow capability of the heads and the planned use is critical. This factory-based 5.9L Magnum has since been dropped between the fenders of a 1974 Plymouth Duster owned by HOT ROD tech center technician Chris Arriero; it will see mostly street use with occasional autocross and road course action. The 10.4:1 short-block has a Comp Cams Mutha Thumpr hydraulic-roller camshaft with 0.556/0.542 inches of lift (using 1.6 rockers) and 235/249 degrees of duration, ground on a 107-degree lobe separation angle. When talking about an engine for a hot street car, this is smack-dab in the middle of Goldilocks territory. Chris will be able to run on ordinary 91-octane pump gas without detonating, and the valve timing will provide enough flow to produce serious power without causing ill manners or bleeding off too much cylinder pressure.

See all 52 photos Edelbrock's Performer RPM AirGap dual-plane intake (part No. 7576, $327.52 Summit) is hard to beat for a small-block Mopar on a hot street machine. In fact, it's the main reason we wanted to use the EQ cylinder head with the LA-series intake bolt pattern in the first place.

Our compression, cylinder heads, and cam choice all point to using an intake manifold that will accentuate performance on the street with lots of off-idle grunt, a fat midrange, and a top end that holds on until the limit of our modest valvetrain is reached—about 6,000 rpm. Going with anything bigger means spending a bunch more on everything from valvesprings and rockers, to big headers and a bigger fuel system. Mission creep is the biggest problem the DIY engine builder faces, so we firmly staked out our street territory with Edelbrock's Performer RPM AirGap intake. This piece is a third-generation dual-plane design that maximizes all the benefits of a dual-plane (wide powerband, good street manners, thermal management) while modestly stretching its capability into race territory.

See all 52 photos For our dyno test, we checked out a pair of double-pumper carbs, both of them Street-Q Series units (650 and 750 cfm) from Quick Fuel Technology.

QFT Carburetion

In the universe of carburetors there are many great choices. Chances are, you have several in your garage that you'll probably dust off for a build-up like this, but if you do decide to buy new, one of Quick Fuel Technology's Street-Q units would be a sound choice. The Street-Q series is chock-full of racer features and comes in a bunch of sizes (650, 750, 850, and 950 cfm). They are unbelievably inexpensive (our 650 cfm unit costs just $482), they're offered with either vacuum or mechanical secondaries, and they have the full range of tunability.

Ours was almost perfect right out of the box, only needing a slight drop in primary jet size to get our air/fuel ratio right in the 12:1 sweet spot. By having a square bore footprint and a modular Holley 4150 architecture, it's easy to dive right into a QFT double-pumper. With high-end features like adjustable high-speed air bleeds, four-corner idle mixture, two-circuit metering, large sight glasses on the bowls, adjustable secondary linkage, and downleg boosters, even the serious racer will feel right at home with the Street-Q.

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Pertronix Ignition for Mopar

Driving our ignition system choice was a couple of things. Obviously, we wanted to keep the price down, but we also wanted a stock look. We arrived on the Pertronix Flame Thrower (part No. D7144600, $249.97 Summit) cast-look distributor for both these reasons, but we also liked the fact that it had Pertronix's new Ignitor III ignition module mounted deep inside. This little jewel brings any vintage muscle car into the modern age with stuff like an adjustable digital rev limiter, multi-strike capability all the way up to redline, and five times more spark energy than a points system.

Digging deeper, we liked the adaptive dwell, which like an HEI, expands the dwell time as rpm increases, meaning your coil will have plenty of juice—even at high rpm. It's a mean little distributor, and when paired with Pertronix's Flame Thrower III coil with 45,000 volts (at just 0.32 ohms), it makes for a power-packed combo. Carrying the sizzle to our NGK FR5 plugs was a set of universal 8.8mm Flame Thrower wires. All in, our Pertronix bill came to around $360, but given that we've seen marginal vintage ignitions cost as much as 50 hp on the dyno, it's a price we were willing to incur.

Patriot Long-Tube Headers

It's common practice for dyno operators to use the same set of headers on the dyno for the sake of simplicity. These are often large-diameter, long-tube step headers that easily clear the dyno apparatus, and that produce big numbers on the screen due to their optimized design. In practice, however, these dyno headers rarely fit into real cars like Arriero's 1974 Duster. For that reason, we ordered a set of Patriot 1 5/8-inch diameter long-tube headers with a block-hugging design (part No. H8206-1, $406.97 Summit).

These are specifically for a Chrysler small-block being used in an A-Body, so their various twists and turns are designed to clear steering and suspension components without rubbing on sheetmetal. Being a long-tube design, they also boost horsepower and torque, widening the powerband in the process. An attractive ceramic metallic coating further adds to performance and holds the inevitable corrosion at bay. We think the Patriot long-tubes were a good choice, producing nice power even though they weren't optimized for the dyno environment. The good news is that thanks to our Patriot long-tube headers, the numbers we got for the 360ci Magnum will mirror what it puts out in Chris' Duster.

See all 52 photos Parts and machine work for the 360ci Magnum for Arriero's 1974 Duster cost about $4,000. If you want IMM to build it for you, it will run between $6,000 and $6,500, depending on options.

On the Dyno

With our long-block assembled, loaded on the dyno, and filled with Torco 10w30, Brian Hafliger of IMM Engines ran a tuning loop on the 360ci Magnum, adjusting the total timing to 34 degrees and making a minor adjustment to the primary jetting. With everything up to temp and checking out, it was time to make a full power pull, first optimized with the 650cfm Street-Q carb. We had our sights set on a solid 430 hp—about what a similar vintage Vortec small-block Chevy might produce with similar equipment. What we got was 461 lb-ft at 4,500 rpm and 454 hp at 5,800 rpm. The little Street-Q blew us away, so we were understandably eager to try the larger 750.

Typically, a larger carb on an engine equipped like ours would be worth 5 to 10 hp more at key points in the power curve, but once we had optimized our jetting for the bigger 750, it turned out not to be so. That said, the big double-pumper produced 465 lb-ft of torque at an even lower 4,400 rpm (+4 lb-ft), and 455 hp (+1 hp) at the more elevated speed of 6,000 rpm. Average torque increased by 2 lb-ft, and average power improved by just over 2 hp. That's pretty much a wash—not enough to really feel in the seat of your pants—but since the price difference is only $36, probably still worth the money.

5.9L Magnum Small-Block Dyno Results QFT 650cfm Carb QFT 750cfm Carb RPM: TQ: HP: TQ: HP: 4,000 453.9 345.7 449.6 342.4 4,100 458.1 357.6 458.2 357.7 4,200 460.2 368 461.8 369.3 4,300 460.8 377.3 462.6 378.8 4,400 461.3 386.5 465.8 390.2 4,500 461.7 395.6 465.2 398.6 4,600 460.3 403.2 464 406.4 4,700 459.4 411.2 460.4 412 4,800 456.6 417.3 458 418.6 4,900 451.6 421.3 451.5 421.2 5,000 447.7 426.2 455 433.1 5,100 444.8 431.9 450.3 437.3 5,200 440.6 436.2 445.1 440.7 5,300 435.2 439.1 431.3 435.3 5,400 426.5 438.5 432.3 444.5 5,500 421.1 441 426.4 446.5 5,600 411.9 439.2 420.9 448.8 5,700 413.6 448.9 415.4 450.8 5,800 411.7 454.7 410.1 452.9 5,900 402.3 451.9 404.6 454.5 6,000 397.9 454.5 398.6 455.4 Ave: 439.9 416.5 442.2 418.8 Show All

See all 52 photos Before beginning any engine build, you'll want to clean and inspect the block. Since salvage cores are plentiful and cheap, Magnum cores with cracks or severe wear should be discarded. At this point, our 5.9L block has been cleaned, inspected, and magged.

See all 52 photos A check of the bores revealed they were well preserved. Our 4-inch bore was brought back to life with a clean-up from a ball-brush hone. Only after the bore is established and the main and crankshaft journals are checked should rings, pistons, and bearings be ordered. For an engine of our expected power level, it is not necessary to perform more costly operations like deck equalization, torque-plate honing, or hot honing.

See all 52 photos Our late-model Magnum core took fresh main bearings in the standard size (King MB5534SI, $43 from Summit). Even with a core in good condition, the bearings should always be replaced.

See all 52 photos Here, the main bearing caps receive fresh King bearings. Note how the main caps are numbered and that the center cap is the home of the thrust bearing, identified here by how the bearing wraps around the side of the cap.

See all 52 photos You'll need a short-block gasket set (FelPro CS98982, $58 from Summit) which contains new front and rear main seals, oil pan gasket, water pump gaskets, and fuel pump gasket. Here, the rear main seal is getting a dab of RTV silicone to hold it in place. Care should be taken not to get any on the seal lip or else leaking will occur.

See all 52 photos Before the crank goes in, a good assembly lube should be used to coat all the bearing surfaces.

See all 52 photos Since our power level will always be well below 600 hp, we decided to reuse our factory cast-iron crankshaft. Before dropping in the crank, polish and clean all the bearing surfaces. Once in place, the crank should glide easily without binding.

See all 52 photos We also reused the factory main caps and bolts; they are fine for this power level and saved us some money. The bolts were cleaned and lubed with 30-weight oil, then torqued to 85 lb-ft.

See all 52 photos A critical operation you'll want to perform is checking the crankshaft endplay once the main caps are torqued down. You want to see between .004 and .008 inch of play. Ours specced out at .004 inch.

See all 52 photos A new double-roller timing set is cheap, and it's good insurance for a stable valvetrain. This Mopar Performance timing set (P5249267, $69 from Summit) was bolted on with a mechanical fuel-pump eccentric on it.

See all 52 photos Before we began, we found ourselves at a crossroads: Do we save money and stick with the stock cast pistons—limiting our compression, valve diameter, and valve lift—or do we step up to forged slugs? This forged piston from Icon (IC741-STD) would bump our compression ratio to 10.4:1 (from 9.1:1), giving extra room for our 2.02-inch intake valves and allowing a higher-lift cam. Being the same weight as stock, they don't require the rotating assembly to be balanced either, saving us a bit more cash. At just $627 a set, the Icon pistons were a no-brainer.

See all 52 photos IMM cleaned up our stock forged rods and press-fit the pins with this tool. You'll want a real machine shop to do this for you; IMM charges $55 for this operation (set of eight).

See all 52 photos The Icon pistons come with a Keith Black ring set (1/16, 1/16, 3/16) which includes file-fit ductile-iron top and plasma moly second rings. For our naturally aspirated 4-inch bore street motor, we want about a 16-thousandths gap on the top ring and 20-thousandths on the second ring.

See all 52 photos IMM likes to place the top ring gap under the intake valve relief and the second ring gap at the exhaust valve relief, making them roughly 180 degrees apart.

See all 52 photos Before installing the pistons in the block, press in the new rod bearings (King CR805SI, $22 from Summit) and smear a dab of assembly lube on them.

See all 52 photos This handy ring compressor is used to guide the rings into the bores; a piston knocker is used to urge the assembly into place. Beforehand, you should apply a thin film of 30-weight oil to the cylinder bores. Note that it's critical to observe both the rod cheek and intake valve orientation along the engine's north-south axis (rod chamfers along crank throws, piston reliefs matched to valves).

See all 52 photos Once again, the factory rod bolts were cleaned and reused. After inserting new rod cap bearing shells, the bearings were lubed and the caps attached with a speed wrench. A film of 30-weight oil should be applied to the bolt threads and the underside of the bolt head before torquing to 50 lb-ft.

See all 52 photos While you might be inclined to believe all cam and timing gear manufacturers are perfect, mistakes do get made in manufacturing. Don't just line up the timing gear dots and let it eat; the time you don't verify the valve timing with the cam card is the time you'll invite mechanical carnage.

See all 52 photos We won't go into detail on how to set up and check camshaft timing here, but we will show you that the math worked out just as advertised with the cam checking in with a lobe separation angle of 107 degrees.

See all 52 photos We'll be reusing the oil pickup from the salvage core but replacing the oil pump with a high-volume Melling pump (M72HV, $70 from Summit). This pump will deliver 20 to 25 percent more volume than stock. IMM likes to increase the pressure threshold of the pump by adding a shim (actually a washer) between the spring and the plug.

See all 52 photos We'll be reusing the oil pickup from the salvage core but replacing the oil pump with a high-volume Melling pump (M72HV, $70 from Summit). This pump will deliver 20 to 25 percent more volume than stock. IMM likes to increase the pressure threshold of the pump by adding a shim (actually a washer) between the spring and the plug.

See all 52 photos Here, Fred Hafliger of IMM Engines pours Torco break-in oil directly into the lifter valley.

See all 52 photos Modern hydraulic roller lifters can be reused with no problem on a stock rebuild, but in a performance street application like ours, new ones are good insurance. This set of 16 Mopar Performance lifters (part No. P5249862, $129.97 from Summit) is getting a shot of assembly lube before being dropped in. They're being paired with a hydraulic-roller Comp Mutha Thumpr cam (0.556-/0.542-inch lift with 1.6 rockers, 235/249 degrees duration at .050 inch lift).

See all 52 photos Links bars ensure that the roller on the lifter is aligned parallel to the surface of the cam lobe. The stock ones can be reused as shown here.

See all 52 photos The lifter link bars are locked in place by the link bar spider (reused from the original core). It bolts to the centerline of the block in three places.

See all 52 photos These iron EngineQuest CH318B Magnum heads were prepped by IMM Engines and are designed with an LA-series intake bolt pattern. IMM has machined them for larger 2.02-inch intake valves, given them a larger throat diameter, and they've been hand-blended in the bowl area. They cost $1,469 (pair) and flow around 266 cfm at 0.600-inch lift.

See all 52 photos We've discovered that Hughes Engines also offers several cool versions of the EngineQuest CH318B cylinder head, including a Super-Prepped Ram CNC head ($2,300.20/pair, assembled), which comes with 2.02-/1.62-inch stainless valves and bronze valve guides. The added CNC work has the potential to push output well above 500 hp, depending on compression, fuel octane, and camshaft specs.

See all 52 photos The IMM-prepped EQ Magnum head supports flow for over 400 hp with larger stainless Ferrea 6000-series 2.02-inch intake valves. The exhaust valves are smaller-diameter 1.60-inch semi-tulip Ferrea valves, which pick up flow everywhere compared to the larger 1.625-inch stock nailhead valve in the stock Magnum head. Both valves are 0.035-inch longer than stock to maximize valvetrain geometry with the higher-lift cam. IMM cuts the spring seat pocket to an additional depth of 0.100 inch for a 1.325-inch-diameter beehive spring with a 1.75-inch installed height.

See all 52 photos A set of FelPro 1008 head gaskets (0.039-inch compressed height) was used with the cleaned-up stock fasteners torqued to 50, then 105 ft-lb (twice) using 30-weight oil on the threads and under the bolt heads. Start your torque pattern at the center and spiral out for the most even clamping load.

See all 52 photos Unlike LA-series heads that use a pedestal-style rocker arm arrangement, the Magnum series V-8 has stud-mount rocker arms and guideplates to stabilize valvetrain motion. We're using Comp guideplates (part No. 4825-8, $19.41, Summit) and hardened 5/16-inch screw-in studs (part No. 4504-16, $61.99, Summit). These get torqued to 25 ft-lb with 30-weight oil.

See all 52 photos Chevy rocker arms (Comp part No. 17002-16, $172.97 Summit) and 6.900-inch long Ford pushrods (Comp part No. 8313-16, $200.99 Summit) make for strange bedfellows in a Dodge engine, but the extra lift from the 1.6 rocker ratio and the extra pushrod length means more flow and better valvetrain stability. Combined with LS beehive springs, you can see the combo clears with room to spare at full valve lift.

See all 52 photos A new or remanufactured water pump can be had from Summit or Rock Auto for $20 to $30 and will depend on your accessory drive and vehicle. This long-snout unit works in Chris' 1974 Duster.

See all 52 photos When setting preload on a hydraulic roller valvetrain, take all the slack out of the rocker with the lifter sitting on the heel of the cam, tighten the polylock one turn, then lock it in with the Allen wrench.

See all 52 photos Now is a good time to prime the lube circuit and check the supply of oil to the valvetrain. A cordless drill with a hexagonal drive extension fits into the oil pump drive, and a simple mechanical oil pressure gauge monitors pressure. We saw a strong 60 psi on the gauge with a steady stream of oil dribbling from the pushrod weep holes. Now's the time to investigate and fix any lube problems before you put fire in it.

See all 52 photos The beauty of the EngineQuest CH318B cylinder head is that it allows us to use a common LA-series intake manifold on a later Magnum engine, which means you'll need LA-series intake manifold gaskets (Felpro part No. 1213, $23.60 Summit). Cyclo Ultraweld High-temp RTV sealer goes around all water passages.

See all 52 photos After setting the intake gaskets in place on the RTV, put more on the top side of the gaskets around the ports, water passages, and on the ends of the block. You won't want to wait long before setting your intake manifold on top.

See all 52 photos After loosely snugging all the manifold bolts, tighten them up after an hour once the RTV has had a chance to firm up. This will improve the seal over going full torque while the RTV is still wet.

See all 52 photos The Edelbrock AirGap intake includes several pipe plug fittings that need to be installed using liquid Teflon (sparingly) and an Allen wrench.

See all 52 photos The oil pump drive is installed next. Apply assembly lube liberally to the distributor gear before dropping it in and indexing it with a thin pair of needle nose pliers.

See all 52 photos We went upscale with a pair of ribbed and polished cast-aluminum valve covers from Mopar Performance (part No. P5007618, $239.97 Summit). They have the Magnum bolt pattern, plenty of room for our larger valvetrain, and fit the 5.9L perfectly.

See all 52 photos Firing our NGK FR5 plugs (one heat range hotter than stock) is a set of universal 8.8mm Flame Thrower ignition wires from Pertronix (part No. 808280, $57.97 Summit). We opted for a custom set so that we can avoid arcing as we route our wires around a set of Patriot long-tube block-hugging headers.