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Holley Ultra HP Carburetor atop an LS Engine

Best Of Both Worlds

Aug 22, 2013
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If you're a consistent reader of this magazine, then you've no doubt seen us extol the virtues of the LS family of engines ad infinitum. Our love affair with this amazing engine is based on science, and not just an infatuation with the "latest and greatest." After all, what's not to love about a lightweight aluminum engine that puts out so much performance per cubic inch? But there is a downside to this engine that many gearheads find daunting, and that's the computer and associated octopus of wiring required to get an EFI-fed LS engine in a car and running. Sure, thanks to the aftermarket it's easier today than it was, but many, especially those already well-versed in how to fiddle with a carburetor, prefer the simplicity of the older small-block Chevy engines. Well, it's possible to greatly simplify the addition of an LS engine to your Camaro by forgoing the EFI and feeding the LS with a carburetor.

Ls 2/24

To see what's involved and dyno-check the power potential of rolling old school with a carb, we followed along with a stroker LS3 build over at Don Lee Auto in Rancho Cucamonga, California. For this build, owner Tim Lee, wanted the benefits of LS power but preferred to not deal with trying to wire and tune an ECU.

01. Our starting point was this new Chevrolet Performance 376ci (6.2L for the metric crowd) aluminum block. Since displacement is power, we honed the bore out to 4.070-inches and decided to run a 4-inch-stroke crank, which will team up to give us 416 inches of glorious LS power.

Ls Engine 3/24

02. What stick you decide to stuff in the engine will ultimately determine its personality. Go super aggressive and you'll make more power, but it won't be happy cruising around town. We consulted with the cam gurus over at COMP and came up with a profile that should yield gobs of power and have nice enough manners for a Sunday cruise. The final specs on the XE-R cam were 238/240 with lift numbers of .605/.609 on a 112 LSA.

Comp Cam Xe 4/24

03. The heart of any stroker is the crank. For this build, we decided to try one from Eagle. This 4340 steel ESP LS crank came Magnafluxed, sonic-tested, and stress-relieved for longevity and improved bearing life, plus it won't break the bank in terms of cost. This 58x reluctor-equipped crank (PN 442740006100) set us back just over $800.

Eagle 4340 Steel Esp Ls 5/24

04. We also picked up a set of Eagle's connecting rods. The 6.125-inch billet 4340 steel H-beam rods (PN CRS612503D) came in a weight-matched set and priced just under $500. For pistons, we went with forged Mahle PowerPak flat tops (PN L92105070F04, $690). They came with a Grafal anti-friction coating on the skirts and are phosphate coated to reduce pin galling. The crank, rods, and pistons came in a balanced and ready-to-install kit from Eagle.

Eagle Connecting 6/24

05. After file-fitting and installing the rings, we slid the rod and piston assemblies into place and torqued them to spec. Made from 4032 low-expansion aluminum, these flat-top pistons should yield us an 11:1 compression ratio.

Mahle 7/24

06. Before the heads could go on, we needed to install the lifters along with the GM plastic lifter trays. We went with offerings from COMP (PN 850-16, $210) since they drop in just like the factory lifters and are easy on the wallet.

Comp 8/24

07. For heads, we went with these RHS cathedral port pieces (PN 54320-05TS). The 232cc heads came with 68cc combustion chambers, and their Clean Cast technology creates "as cast" ports that are comparable to ported heads. The fully assembled heads featured 2.055-inch intake and 1.600-inch exhaust valves.

Racing Head Service 9/24

08. To ensure a failure-free seal between the heads and the block, we installed a pair of Fel-Pro MLS head gaskets (PN 26192PT). We also ran a set of ARP Pro-Series head studs (PN 234-4317, $330).

Fel Pro Mls Head 10/24

09. We then turned our short block into a long one by installing the RHS heads and torquing them in place. We should note that by the time you read this these cathedral port LS heads will be discontinued by RHS. They have a new, higher flow, small-bore head coming out that's based on the LS7 design. We can't wait to check them out!

Racing Head Service Heads 11/24

10. To finish off our valvetrain, we went with a set of COMP Ultra-Gold aluminum rocker arms (PN 19024-16, $460). These CNC-machined rockers are some the best COMP offers and won't fail when pushed hard. For pushrods, we ran COMP Hi-Techs (PN 7956, $135).

Comp Cams Ultra Gold Aluminum Rocker 12/24

11. LS engines aren't what we call "pretty," but they can easily be made to look a lot better than stock. One way are these new valve covers from Holley (PN 241-91, $175). They retain the location of the coil packs but are a lot better looking than their stock cousins. They are also a touch taller than stock and will work with all ignition coils that have 72mm bolt spacing.

Holley Valve 13/24

12. To hold the oil and facilitate a drama-free installation into a classic Camaro, we installed this 5.5-quart Holley Retro-Fit oil pan kit (PN 302-1, $400). The kit included the sump baffle, pick-up tube, sump plug, oil filter stud, and oil passage cover. For this pan we did have to go to our local GM dealership and buy an LS3 dipstick (PN 12634547) and tube (PN 12625031).

Holley Retro Fit Oil Pan 14/24

13. To run a carbureted intake we needed to go with a suitable intake gasket. In this case, what we found were these Fel-Pro pieces (PN 1312-3, $60 a pair). You can also see how we had to clearance the edges of the LS3 valley cover to clear the runners on the new aluminum intake manifold. The valley cover was secured using stainless six-point fasteners from our ARP accessory bolt kit (PN 534-9605, $370).

Fel Pro Intake Manifold 15/24

14. For maximum performance, we picked up this Edelbrock single-plane Super Victor LS intake manifold (PN 28097, $500). The carb-mount pad is 1.12-inches taller than their Victor Jr. and the port exits are increased a bit for more flow.

Edelbrock Single Plane Super Victor Ls 16/24

15. To top off our engine, we went with Holley's new Ultra HP carburetor (PN 0-80804HB, $785) since the 850-cfm size is perfect for our stroker. The carb features ultra-lightweight aluminum construction along with "bright dipped" billet metering blocks and 4150 base for more strength than cast pieces. The bowls feature internal baffling to limit fuel slosh when launching hard or cornering. As a bonus, it's easy to adjust the fuel level due to glass fuel level windows in the bowls.

Holley Ultra Hp 17/24

16. When this engine finds its way into a Camaro it's going to need a throttle plate, so we decided to check out this hot-off-the-shelf offering from Lokar (PN TCB-4150, $150). They are known for turning out beautiful and functional billet widgets, and this was no exception. The first step was setting the 4150 aluminum throttle plate in place.

Throttle 18/24

17. And here it is with the dual springs and cable mount attached. The Lokar piece also came with provisions for a transmission kick-down cable.

Holley Ultra Hp Carburetor 19/24

18. When building an LS engine from scratch, most people forget that they need to buy a set of coil packs. Until recently that meant going to the GM dealer to shell out around $100 per coil for stockers. Now, Granatelli Motor Sports is offering these direct replacement coils (PN 28-0513CP, $575), which are rated at 80,000 volts and have a lifetime warranty. We paired this up with a set of Granatelli's 8mm "near zero OHM resistance" plug wires (PN 28-181HTY) They flow about 25 percent more power than stockers and have 500-degree boots to help ensure survivability.

Granatelli Motor Sports Coil 20/24

19. And with that our 416 carbureted stroker was done and ready for some quality time on the engine dyno.

Ls 21/24

20. After strapping the 416 to Westech Performance's Superflow 902 engine dyno, we filled the mill with 6 quarts of COMP's 10w-30 Muscle Car oil. This is perfect for cars without catalytic converters, as it's loaded with zinc and phosphorous.

Comp Cams Engine 22/24

21. Running a carburetor on your LS build does negate the need for an ECU and the myriad of wires that accompany it, but the coils still need something to tell them when to fire. Enter this MSD 6LS ignition controller (PN 6012, $320). This small unit came with a wiring harness, which plugs into the crank sensor, cam sensor, and the coil packs. It also allows for the optional use of a MAP sensor. It was easy to install and is programmable via a computer port so that timing, rev limiter, step retard, and idle timing can easily be adjusted.

Msd 6ls Ignition 23/24

22. After a few pulls we had the 416 mill dialed in with a best pull of 617 horsepower and 553 lb-ft of torque. At 3,500 rpm, the torque was just shy of 500 lb-ft with peak at 5,200. When the engine was making peak horsepower at 6,500 rpm, it was still pumping out 500 pounds of twist. That makes for a nice, flat, and fun torque curve.

Dyno 24/24


Westech Performance
Mira Loma, CA 91752
Mahle Motorsports
Fletcher, NC
Racing Head Service
Memphis, TN 38118
Eagle Specialty Products, Inc.
Southaven, MS 38671



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