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551 hp and 515 lb-ft of torque from a worked over LS1

Expansion Plan: The LS1 is a great engine that can be made even be better with just a touch more displacement!

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Everyone loves to get the latest and greatest. It’s human nature and it afflicts gearheads just like everyone else. Yeah, a top-of-the-line LS7, LS3, or even the new-gen LT mill under your hood is something worth aspiring to, but there are a ton of other LS options out there just begging for some attention. One of these is the LS1. Yep, the engine that changed everything just over 20 years ago is still a great mill with a ton of potential. The good news is that since people are focused on the new and shiny they to ignore these earlier LS variants, and that means they are out there for a reasonable price.

Turning a Gen I 350 small-block into a 383-inch mill has been a staple of the hot rodding world for decades, so it shouldn’t come as a shock that it’s a great way to coax more power of older Gen III LS1 (346-inch) mills. All it takes is a slight hone of the cylinder walls and a 4.000-inch stroke crank to get that LS1 displacing 383 glorious inches, more than its 376-inch LS3 cousin. Of course, everyone focuses on power, but the real benefit to a stroker is torque. Yep, torque is where it’s really at for a street car since very little time is spent in the top of the rpm range. With that in mind, we decided to work this project with a goal of having killer mid-range torque, and since this engine was destined for 1955 Chevy we didn’t have to worry about hood clearance and could utilize a torque-producing truck-style LS intake manifold. If you have the room under your hood, and aren’t as concerned with peak hp numbers, then it’s certainly an option that should be looked at. So follow along as we teach an old dog a new trick or two.

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1. Our starting point was this old LS1 pulled from a C5 Corvette. LS engines are plentiful in salvage yards and are great starting points for buildups. All we really wanted of this engine was the block, the rest of the parts found a new home in an iron 5.3L LS build.

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2. The best part of this engine is the aluminum 5.7L block, which makes this engine pretty close to 350 cubic inches. And, just like the Gen I 350 small-block, it’s just a hone and stroker crank away from a bump up to 383 cubes. The block was sent over to Rancho Machine who took the bores from 3.898 to 3.905 inches. More displacement means more torque, and the extra cubes will make a bigger cam even easier to live with.

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3. The main gain in displacement came from the Scat 4.000-inch stroker crank. The forged 4340 crank offers a lot of bang for buck and came shot-peened, heat-treated, precision ground, and ion nitride treated for added strength. Scat also goes further by lightening the throws and gun-drilling the mains, as well at adding lightening holes in all of the rod journals. This crank came as part of fully balanced rotating kit from Summit Racing (PN SCA-1-44000BI) that included the crank, rods, pistons, rings, and bearings needed for our 383 LS build.

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4. We opted for a 24x reluctor wheel, but the kit is available with the newer 58x reluctor as well in case you’re running a newer ECU. You can also see some of the nice finish work on the crank, such as the chamfered oil holes. For main bearings we used the supplied Clevite pieces (PN MS-2199H).

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5. For connecting rods the kit came with Scat 4340 6.125-inch I-beam rods. The rods arrived polished and shot-peened to eliminate stress risers and featured hollow dowels and large 7/16-inch cap screws. As an added bonus they came profiled and clearanced for our stroker application. The one-rib cap design adds even more strength due to additional bearing support.

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6. The Scat rotating kits come with various pistons (depending on application) and ours included a full set of forged aluminum Race Tec pieces. The flat-top pistons (+3.30cc) featured two valve reliefs and came with a full set of rings.

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7. Once the pistons were all mated to the Scat rods (and the rings fitted and installed) we could begin sliding them into our freshly honed bores using an adjustable ring compressor.

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8. With all of the piston/rod assemblies installed we could torque down the ARP 8740 12-point chromoly cap screws.

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9. OK, the cam makes the engine, so this is one area where we wanted to “choose wisely” as they say. What we came up with was a Comp XFI XE-R cam (PN 54-448-11 and grind XER287HR). We’re running a cathedral port head so there’s no need for the large split as seen in cams for engines like the LS3. This cam also bumps the lift up quite a bit to 0.605/0.609-inch but keeps a fairly street friendly LSA of 112. The aggressive lobe design means it will like running in the upper rpm ranges.

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10. Once we installed the cam plate along with a new timing set from Comp (PN 3158KT) our short-block was done.

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11. When rebuilding an engine it’s always a good idea to toss on a new oil pump, especially when it’s as inexpensive ($67) as the GM one we bought from Summit Racing (PN 12678151). We misplaced a box of fasteners, but fortunately we had some ARP bolts from another project laying around. Note to self: be more organized next time.

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12. Some gaskets on an LS engine are reusable, but head gaskets don’t fall into this category. To seal the deal we used some Fel-Pro pieces that were in the master gasket kit we picked up (PN 2817). You can save some cash by using torque-to-yield factory style bolts, but we’re big fans of the reusable, and much stronger, offerings from ARP (PN 234-4316).

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13. Our early LS1 came with GM 853 heads. These are decent castings but they leave a lot of performance on the table. Besides, we used them on a past iron LS1 engine build we did. For more flow and power, we decided to top our 383 with a pair of Trick Flow GenX 215 cathedral port CNC competition ported heads from Summit (PN TFS-30610001-C01). These came fully assembled with 64cc chambers, chromoly steel retainers, and 13.5-degree valve angles to decrease shrouding.

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14. Our new Holley retrofit oil pan calls out for an early LS1 F-body windage tray, but we’ve found that you can cut down a later windage tray and it will work just fine. The pan instructions also says it shouldn’t work on a 4.000-inch stroke, but it will, just barely.

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15. When running a 4.000-inch or under stroker crank we just love the Holley F-body style oil pan (PN 302-2). This is one of the best pans in terms of frame and steering clearance on the market for those doing LS swaps into classic Chevys. It comes with an anti-slosh baffle, but Holley also offers a real-deal trap-door style baffle system for those doing more serious handling stuff.

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16. And with that our 383 was a long-block.

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17. There are lots of directions you can go when you get to the rocker stage. Choices range from bone stock GM rockers, to stock rockers with upgraded trunnions, or even fully aftermarket roller tip rockers like these Ultra Pro Magnums from Comp (PN 1675-16). These pieces are rock solid with extra-strong trunnions and the roller tip will function better with our cam’s higher lift numbers.

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18. For valve covers we opted for a set of natural cast finished Holley pieces (PN 241-88). These are a huge visual improvement over factory valve covers since they ditch the added clutter of the coil pack brackets. If you need a bit more room Holley also offers a taller version of these.

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19. This 383 LS1 is destined for a 1955 Chevy so we have plenty of hood clearance to work with. Because of this we had more intake manifold options. This is a street car, so we were willing to sacrifice a little top end power for a bit more low-end grunt. We could have used a GM truck intake, but referring to them as ugly is a bit of an understatement. Instead, we chose a FAST LSXrt 102mm truck style intake (PN 146602B), which should boost our low- to mid-range torque and look good doing it.

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20. We also teamed up this FAST 102mm billet throttle body with the LSXrt intake. Airflow into our stroker LS won’t be a problem.

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21. To feed our 383, fuel was added by a pair of FAST high-flow billet fuel rails (PN 146028B-KIT). These feature a larger internal diameter that helps damp the pressure pulses and the rails have increased volume. These will work with LS truck/SUV injectors but can be configured to work with LS2 style injectors like the FAST 46-lb-per-hour pieces (PN 30462-8) we’re running.

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22. All engines create crank vibrations, so a good damper is pretty important. We went with a TCI Rattler torsional vibration absorber (PN 870030) to counteract these vibrations. The Rattler isn’t really a damper, which converts the vibrations into heat energy. Instead, it uses internal rollers to release energy back into the crankshaft. It’s SFI 18.1 certified so it’s perfect for the street or track. With the Rattler installed, we were ready to haul our 383 LS1 over to Westech to see how it would shake out.

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23. Once mounted to the Superflow 902 engine dyno, and completed with a Meziere electric water pump and Hooker 1 7/8-inch LS swap headers, we were ready to run the 383 LS1 through a break-in cycle. Oh, when we run aftermarket intake manifolds and fuel rails we usually have to make a fuel crossover line to connect the two fuel logs. But, this time we were able to run one of FAST’s new pre-made fuel rail crossover (PN 54028FRC), which was a real time saver.

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24. Our 383-inch LS1 now out-displaces an LS3 (376 cubes and rated at 436 hp in factory crate engine form), so we expected some solid numbers and we weren’t disappointed. The stroker knocked out a best pull (at 28 degrees of timing) of 551 hp at 6,300 rpm with a strong torque number of 515 lb-ft at 4,800 rpm. Having over 400 lb-ft on tap from 3,200 rpm onward will really make this a fun car to drive on the street. This excellent mid-range torque is one of the benefits of the truck-style intake and, on a street car, it more than makes up for any loss in top end power.

Photography the Author

Sources

Don Lee Auto
Cucamonga, 91730
909-989-1573
www.donleeauto.com
Trick Flow Specialties
Tallmadge, OH 44278
888-841-6556
www.trickflow.com
TCI Automotive
Ashland, MS 38603
888-776-9824
www.tciauto.com
Summit Racing
Akron, OH
800-230-3030
http://www.summitracing.com
Westech Performance
Mira Loma, CA 91752
951-685-4767
www.westechperformance.com
Fuel Air Spark Technology (FAST)
Memphis, TN 38118
877-334-8355
http://www.fuelairspark.com
Scat Crankshafts
Redondo Beach, CA 90278
310-370-5501
www.scatcrankshafts.com
Fel-Pro
Southfield, MI 48034
800-325-8886
www.felpro-only.com
Competition Cams
800-999-0853
http://www.compcams.com
ARP
Ventura, CA 93003
800-826-3045
arpdiesel.com
Clevite
662-893-2860
us.mahle.com/mahlemotorsports
Holley/Hooker
270-781-9741
www.holley.com

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