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Testing Holley EFI on a Big-Inch, Big-Block Chevy Engine

The Big-Block EFI Test: Prestige Motorsports tests two different Holley EFI setups on a new 632ci big-block build

Jeff Huneycutt Jun 29, 2018
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Prestige Motorsports has established itself in the last few years as a major player when it comes to horsepower production. The engine builders in Concord, North Carolina, regularly ship engines all over the world, and they are constantly testing and refining new engine recipes in order to stay on top in the horsepower wars.

Prestige already has several big-block Chevrolet packages for everything from 489 to 598 cubic inches and as much as 725 horsepower. But more is always better, so we stopped by to check out the assembly of their newest 632-cubic-inch bruiser.

The goal of this build is an engine that produces locomotive levels of torque throughout the rev range with the ability to do it all day long. It’s based on a World Products Merlin IV cast-iron block with 4.600-inch bores. That, combined with a forged Eagle 4.750-inch stroke crank, makes for 632 total inches for a street machine engine.

We’ll detail the complete build here, but what’s cool is that the mad scientists at Prestige do more engine testing than practically any other engine builders we know. So while this engine was on the dyno, they wanted to test out different EFI setups to see how they would work on this combination.

Prestige has a longtime working relationship with Holley when it comes to their engine management and fuel-injection systems, so both EFI setups will be run off of the same Holley HP EFI engine control unit for consistency in testing. In both tests, Prestige will also use a Holley single-plane, port-injected intake with a Dominator-sized flange and Holley 66-lb/hr injectors.

For the test, we’ll be running one of Holley’s 2,000-cfm, four-barrel billet throttle bodies on a Dominator flange and testing it against an Edelbrock cast-aluminum elbow with a Holley 105mm single-blade throttle body.

The big 632-inch engine will demand tons of air to make maximum power, so it will be interesting to see if the LS-style 105mm throttle body can keep up with the race-spec 2K Dominator throttle body.

So check out the build and stick around for the testing. This should be fun! CHP

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1. The plan for Prestige’s 632ci big-block is a build that produces enough torque to make a diesel locomotive blush. Plus, of course, when you have a brand-new, 750-horsepower engine on the dyno, it’s the perfect time to do a little EFI testing, right?

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2. The foundation for this build is a World Products Merlin IV cast-iron block. This is the 10.200-inch tall-deck version, which will allow extra stroke and the cylinder walls can handle a bore up to 4.600-inches in diameter—which is exactly what we are using.

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3. The camshaft is a solid roller from Comp Cams. It is ground with 270/280-degrees of duration at 0.050-inch lift on 110-degrees of lobe separation. With the 1.7:1 ratio rockers, gross valve lift will be 0.715-inch for the intakes and 0.717-inch for the exhausts.

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4. If you spend most of your time in stoplight-to-stoplight traffic or maybe the occasional dragstrip blast, this may not be necessary. But for extended power runs like road racing, or if you are pushing the limits with power-adders, you may need to add piston squirters. These squirters thread into a 0.1360-inch hole Prestige has machined into the bearing saddle and directs a constant stream of cooling oil to the underside of each piston.

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5. To feed oil to the squirters, a groove approximately 0.040-inch deep is cut into the bearing saddle from the oil feed hole to the threaded opening for the squirter. Once the main bearing is installed, the backside of the bearing will cap the groove to force the oil along the groove and into the squirter.

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6. To get to 632 cubic inches, you need a lot of swept area for the pistons. The crankshaft is a forged unit from Eagle with a 4.750-inch stroke. For comparison’s sake, the 502 big-block has a stroke of just 4.000 inches.

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7. For the rest of the rotating assembly, Prestige went with Eagle for the 6.700-inch long connecting rods and with JE for the forged pistons. The flat-top piston forgings are 4.600-inch diameter with a short 1.125-inch compression distance to help fit a long rod despite all that stroke. That short compression distance puts the pin bore up into the bottom ring land so a support rail for the oil ring is necessary. Speaking of the pin bore, these pistons use a standard 0.990-inch diameter wristpin and the ring grooves are cut for 0.043/0.045/3mm rings.

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8. The Merlin IV block is designed with four-bolt mains for all five of the nodular iron main caps. Here, the 1/2-inch bolts are torqued to 100 ft-lb with motor oil lubricating the threads.

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9. After hanging the pistons on the rods, the rings and piston skirts are given a light coat of oil before getting squeezed into the correct cylinder bores.

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10. And finally, the short-block is locked in and ready to go.

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11. The Canton 9-quart steel oil pan uses baffles and a windage tray to help keep the oil around the pickup tube and minimize power-robbing windage.

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12. World Products knows horsepower fanatics are going to stroke most of the tall-deck blocks they sell so the block comes notched and doesn’t require grinding, but you must check to make sure your oil pan gasket doesn’t hang over the notches. Here, we had to cut the gaskets back to make sure they aren’t exposed inside the crankcase. If they are, the felt gasket will disintegrate and clog up the screen over the pickup tube.

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13. The cylinder heads for this project are AFR’s aluminum rectangular port heads with giant 357cc intake runners. The intake and exhaust runners, as well as the combustion chambers, are all CNC cut, and the 121cc combustion chamber design means Prestige can use the flat-top JE pistons while still running pump gas.

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14. Prestige put the heads on their SuperFlow SF-1020 flow bench to check the flow, and these heads turned out to be quite impressive. At 28 inches of water, they moved 349 cfm at 0.500-inch valve lift and 410 at 0.800 through the intake ports right out of the box using the included 2.300-inch stainless valves.

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15. The intake manifold looks like your standard carbureted single-plane, but it is set up with injector bungs for fuel injection. This is Holley’s high-rise intake with a Dominator-style flange for tall-deck big-blocks. We’re going to run it with both fuel-injection setups for the testing.

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16. That beautiful hunk of billet aluminum on top of the engine is Holley’s universal 2,000-cfm throttle body with a Dominator flange. It uses four 2.250-inch bores to flow lots of air but also to help smooth it out as it enters the intake manifold’s plenum area. We tested the 2K Dominator throttle body both with and without a 2-inch open spacer from High Velocity Heads.

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17. Here’s a closer look at how the Holley intake works with a fuel-injection setup. Both the fuel rails and the 66-lb/hr injectors are from the Holley catalog, and everything bolted up with zero issues.

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18. In some photos you may notice a crank trigger on the front of the engine, but it was disabled for our testing. An MSD distributor is used to route the spark to the correct cylinder. The Holley HP EFI ECU, however, maintains all the engine controls.

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19. Scorpion rocker arms in the stock ratio (1.7:1) are used to activate the valves. The springs, retainers, locks, and stainless valves all came as part of the setup on the AFR heads.

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20. Here’s a look at the engine setup with the 2K Dominator throttle body on the big-block with a 2-inch open spacer. The engine definitely liked the spacer underneath the throttle body. Although it only made three more peak horsepower (773.7 to 776.8), the spacer did help make a bit more horsepower from 4,300 rpm on up.

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21. After finishing up with the 2K Dominator throttle body, the testing continued at Prestige as they bolted up this cast-aluminum elbow from Edelbrock. This style elbow is popular on engines with turbos or centrifugal superchargers where you are routing air from another point in the engine compartment. This isn’t exactly a low-profile elbow, but it has been designed to maximize airflow. You can’t see it in this photo, but the design includes a cast-in internal divider that helps smooth airflow through the elbow and reduces turbulence.

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22. Attached to the elbow will be a Holley 105mm EFI throttle body. Although Holley doesn’t provide cfm ratings for this throttle body, we’ve seen similar setups with an elbow flow 1,100-1,400 cfm, which puts it a bit behind the previous throttle body’s 2,000-cfm capability. Still, we’re interested to see how it compares when it comes to making horsepower because the list price for this unit is only $550 while the 2K Dominator throttle body lists for around $1,000.

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23. On the dyno, the setup using the 2K Dominator throttle body did the best—as you might expect since it has the highest cfm rating—but the elbow and single-blade throttle body held up very well. We saw a difference of 14.5 peak horsepower (762.2 to 776.8), but throughout the power range the difference really only averaged out to around eight horsepower. If you are all-out racing, that’s admittedly a big deal. But for most street/strip applications, considering the cost savings, we don’t think it’s a huge difference. The 105mm throttle body/elbow setup made more than 700 horsepower from 5,100 rpm all the way until we pulled the handle back at 6,200. Maybe more impressive, we never saw less than 630 lb-ft of torque from 2,800 rpm all the way up!

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Photos by Jeff Huneycutt

Sources

Air Flow Research (AFR)
Valencia, CA 91355
877-892-8844
AirFlowResearch.com
World Products
877-630-6651
worldproducts.net
Scorpion Racing Products
Fort Lauderdale, FL
954-779-3600
http://www.scorpionracingproducts.com
JE Pistons
Huntington Beach, CA 92649
714-898-9763
www.jepistons.com
Canton Racing Products
North Branford, CT 06471
203-481-9460
www.cantonracingproducts.com
Holley
Bowling Green, KY 42101
866-388-5120
www.Holley.com
High Velocity Heads
865-573-9151
www.HighVelocityHeads.com
Eagle
Southaven, MO 38671
662-796-7373
http://www.eaglerod.com
MSD
El Paso,
915-857-5200
MSDPerformance.com
Prestige Motorsports
704-782-7170
www.prestigemoto.com

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