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How to Build a 916hp Chevy SB2 V-8 Using Modern Fuel Injection

From NASCAR To Bonneville: Here’s how modern fuel-injection systems helped Keith Dorton build a 916-horsepower SB2

Jeff Huneycutt Mar 17, 2017 0 Comment(s)
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When Chevrolet debuted the SB2 V-8 engine back in 1998, it was engineered and produced for a single purpose: NASCAR Cup racing. That meant solid flat tappet lifters, a mechanical fuel pump, magnetic-triggered ignition, and—of course—a carburetor.

But even though the SB2 was purpose-built for stock car racing, crafty engine builders are finding new and interesting ways to use this engine in ways the engineers never intended. In the strictest sense, the SB2 is really just a new cylinder head design for the traditional Chevy small-block with high-flowing ports and improved valvetrain geometry. In fact, you can even mount SB2 heads on a standard small-block, although the pushrod angles are slightly compromised.

The strength of the SB2 is that it flows incredibly well for a small-block with the standard 4.400-inch bore spacing. That’s great for NASCAR racing where the engines run between 7,500 and 9,000 rpm for hours, but street engines rarely rev to those lofty heights. In fact, from 2,000 to 5,000 rpm, the SB2 can be a bit of a dog—to put it politely.

Engine builder Keith Dorton, owner of Automotive Specialists in Concord, North Carolina, practically knows as much about the SB2 as anyone that doesn’t receive a paycheck from General Motors. Dorton got his start at the famous Holman Moody operation and then went out on his own and built winning stock car racing engines for decades with multiple teams. That even includes a win in the 1990 Daytona 500 with driver Derrike Cope. And since the SB2’s debut in 1998, he’s been building the engine for competition in multiple racing classes and series with great success.

These days, however, Dorton has branched out from stock car racing and started doing some really interesting builds for top custom car builders and even land speed racers. After decades spent working within the confines of the restrictive rules for NASCAR, Dorton says that the relatively thin rulebook for land speed racing has been a refreshing change. “I just like racing,” he says. “I don’t care if we are talking race cars or lawn mowers, I’m going to want to beat you at it. Of course, it only gets better the more horsepower you can make.”

So when the Alamo Hot Rod Parts race team approached Dorton to help them break records in the competitive C/Gas Roadster class, he chose an SB2 to plant between the framerails of their ’29 roadster. “The tendency of the SB2 is that it really doesn’t have much bottom end, so it’s not an ideal choice for something like a street engine. But when it is built right, it really pulls just as hard as anything we’ve ever worked with on the top end,” he says. “And by top end I mean 8,000 rpm and above. To me, it’s really a great choice for land speed racing.”

Automotive Specialists first built the SB2 with a single carburetor, but after Bonneville’s Speed Week was cancelled two consecutive years (2014 and 2015) because of poor surface conditions, Dorton and the team decided to make a few upgrades before finally making it to the salt last year.

The updated engine kept its original long-block, specifically a Chevrolet SB2 block, a short 3.380-inch stroke crankshaft from Callies, custom Mahle pistons with a set of ultra-low drag Total Seal rings, and ported Edelbrock SB2 cylinder heads. Dorton worked with Crane Cams to develop a custom grind for the camshaft specifically for land speed racing. We know it is a solid roller, but that’s about all Dorton will reveal.

“The engine ran well,” Dorton says. “But we’ve been doing a lot of research and development in the time since it was first built and we’ve learned a lot of things about fuel injection that we knew would help this engine.”

The updates were all centered on adding port fuel injection to the SB2 utilizing a fabricated intake manifold that Dorton and his crew had been developing. There simply aren’t any bolt-on EFI kits for Chevrolet SB2 engines on the market so the crew at Automotive Specialists had to science a lot of things out for themselves. But surprisingly, using a little ingenuity they were able to build this one-of-a-kind EFI engine using mostly off-the-shelf components.

And this is where it gets interesting for us. This engine shows that modern EFI systems are smart, adaptive, and capable of running practically any engine. To manage all the systems on their one-of-a-kind, no-holds-barred race engine, Automotive Specialists chose Holley’s Dominator EFI ECU, which you can buy all day long for less than $1,800. And Dorton points out that the engine and Dominator ECU was first tuned on the engine dyno in Concord, North Carolina, which is 700 feet above sea level, and then ran at Bonneville’s 4,200-foot elevation with no problems.

“The self-learning aspect of these modern EFI systems is incredible,” Dorton says. “We will establish a baseline for the EFI with this particular engine on the dyno, and then Holley’s Dominator system basically could handle it from there. Here in North Carolina, we’ve got a lot of humidity, and if the barometer ever gets below 29 inches that means there must be a tornado outside. And then you haul to Bonneville, Utah, where there is no humidity, you are nearly a mile higher and the barometer might be 27.50. So the conditions were very different, but tuning was never an issue.

“With the dramatic variation in weather at Bonneville, that’s a big help. For example, we set a record mark somewhere around 4 o’clock in the afternoon when it was nearly 110 degrees. And then you go to impound and have to make a backup run first thing the next morning. You may be making that return run right after sunrise with the air nice and cool. You can’t even drive the car around in the pits or impound area, but the engine management system handles the changes right there in the run, and we didn’t have a problem.”

Owing to the SB2’s ability to move incredible amounts of air in the upper rpm ranges, the fuel-injection conversion utilizes not one but two of Holley’s 2,000-cfm universal Dominator-flange throttle bodies mounted on a custom intake manifold. With the throttle bodies it is a snap to hook up throttle position and manifold absolute pressure sensors, but some of the other sensors took a little more work.

In land speed racing, aerodynamics are just as important as horsepower, so the engine and entire driveline must stay tucked behind the ’29’s sheetmetal in order not to ruin the car’s admittedly poor aerodynamic qualities. To help keep the engine as compact as possible, Dorton chose a damper from ATI with magnets built into the shell to trigger the crankshaft position sensor, eliminating the need for a separate flywheel bolted to the front of the damper. Likewise, the cam gear was also machined with inserts for magnets to trigger the cam position sensor. Finally, the individual Holley coil packs are mounted on top of the valve covers to be as close to the spark plugs as possible.

Keith’s son Jeff handles most of the engine tuning and says that the extra adaptability port fuel injection, individual coils, and computer controls means that engines can be more efficient and squeeze out even more power. “On this engine, we monitor the air/fuel ratio on each bank and exhaust gas temps for each cylinder,” he says. “So, by pulling that info, and with an individual coil for each spark plug, we can configure ignition timing for each cylinder and even adjust the amount of fuel each cylinder receives. In some situations we’ll vary the ignition timing per cylinder as much as four degrees to get the best fuel burn. Obviously, you can’t do that with a carburetor.

“After making the switch to fuel injection, we were able to squeeze about another 20 horsepower out of this engine. Now, of course, this engine was at nearly 900 horsepower before, and we’re making 916 now at 9,300 rpm. But when you are hunting for every bit of power you can find, that’s still a pretty big deal.”

Dorton does caution that when swapping to EFI, it is crucial to make sure your fuel system is up to the task. Automotive Specialists has built naturally aspirated and supercharged carbureted engines making 900 horsepower before, and knows that the fuel pump must be able to supply 400 pounds per hour of fuel to make that level of power.

But to keep the 66 lb/hr Holley fuel injectors operating properly, Dorton found that the fuel supply had to be cranked up—way up. After significant testing, he found that this engine needed a big Aeromotive electric fuel pump providing a full 1,000 lb/hr fuel supply to keep those big injectors happy. The message here is not to cut corners when it comes to your fuel pump and plumbing.

So how did the Alamo Hot Rod Parts race team and their EFI SB2 do at Bonneville, you ask? Pretty good … until racing happened. Dorton tells us that they were shooting to break the record in C/Gas Roadster, which was approximately 231 mph, although another team quickly broke the record and bumped the mark up to 234.

After a few shakedown runs and a gearing change, the team made a very impressive run at 238 mph—a 4-mph bump over the record. That got the team an invite into the impound lot where the car would be held until it could make a return run the next morning to back up the time and officially set a new record.

Unfortunately, although the roadster definitely had the speed to bring home a record, the real world got in the way. “In order to set a record, you have to make a return run in the opposite direction the next day, and the average of your two runs is your speed,” Dorton explains. “The course the next morning just wasn’t in the best condition and our driver spun out.

“But hey, that’s what makes racing at Bonneville so much fun. The salt changes every day and you just have to deal with it. We’ll take what we learned and go back next year to make another run at it.

“There’s always going to be records to break.”

Fuel Injected 900 Horsepower Chevy Sb2 001 2/11

1. Although we’re sure the team of engineers at GM never envisioned a port fuel injected setup when they first designed the SB2 engine for NASCAR racing, we think it’s a pretty good look for this powerplant.

Fuel Injected 900 Horsepower Chevy Sb2 002 3/11

2. To move enough air through the Chevrolet SB2 at 9,300 rpm, engine builder Keith Dorton of Automotive Specialists found he needed dual 2,000-cfm Holley Dominator-sized throttle bodies mounted on a custom intake manifold.

Fuel Injected 900 Horsepower Chevy Sb2 003 4/11

3. To maintain the best possible aerodynamic profile means everything has to fit underneath the relatively tight confines of the ’29 roadster’s hood. Here, you can see the fabricated camshaft position sensor extending through the timing cover. Instead of separate flywheels to trigger the sensors, Dorton used a cam gear and an ATI damper with magnets embedded in them to monitor camshaft and crankshaft positions.

Fuel Injected 900 Horsepower Chevy Sb2 004 5/11

4. Valvespring oilers become necessary when you are running 9,300 rpm (or more) at WOT for over 5 miles. These lines feed the oilers that are actually machined into the valve covers.

Fuel Injected 900 Horsepower Chevy Sb2 005 6/11

5. Individual Holley coil packs allow the Dominator ECU to be set up to vary the timing on each cylinder according to its needs. Jeff Dorton, who handles the engine tuning, says it is sometimes necessary to vary the timing between cylinders as much as four degrees in order to get optimal power.

Fuel Injected 900 Horsepower Chevy Sb2 006 7/11

6. Dorton helping to put the final touches on the 370-cubic-inch SB2 after it has been squeezed between the framerails of the ’29 roadster.

Fuel Injected 900 Horsepower Chevy Sb2 007 8/11

7. On the dyno, Keith Dorton (left) runs the engine controls while son Jeff Dorton (right) monitors the fuel maps. Dorton said a big advantage of the modern EFI systems and engine controls is you can build and tune an engine in North Carolina at 700 feet of elevation, then haul the engine out to Bonneville—which is nearly a mile high in elevation—and still trust the computer to make the necessary tuning changes.

Fuel Injected 900 Horsepower Chevy Sb2 008 9/11

8. Besides improved engine control, Dorton says he chose to swap to EFI with a Dominator EFI ECU running engine controls because the team really wanted to add traction control. The Holley unit easily adapts to work with an external traction control module as well as extensive data logging with a Racepak unit.

Fuel Injected 900 Horsepower Chevy Sb2 009 10/11

9. In order to keep the big 66 lb/hr injectors happy, Dorton found it was necessary to bump the fuel supply way up. After extensive testing he finally settled on a high-flow Aeromotive electric pump, which you can see just in front of the engine, because it is capable of supplying over 1,000 pounds of fuel per hour.

Fuel Injected 900 Horsepower Chevy Sb2 010 11/11

10. Jeff Dorton (left) monitors engine controls from his laptop the first time the SB2 is fired up in its new home.

Automotive Specialist’s 370-Cubic-Inch SB2
RPM Torque Horsepower
5,000 438.1 417.1
5,100 449.7 436.7
5,200 459.2 454.6
5,300 466.5 470.8
5,400 477.9 491.4
5,500 484 506.9
5,600 492.8 525.4
5,700 494.9 537.1
5,800 499.5 551.6
5,900 505.8 568.2
6,000 511 583.8
6,100 518.8 602.5
6,200 522 616.2
6,300 529.7 635.5
6,400 530.5 646.4
6,500 540.4 668.8
6,600 540.9 679.7
6,700 546.3 697
6,800 546.7 707.8
6,900 549.4 721.7
7,000 554.4 739
7,100 552 746.2
7,200 553.8 759.2
7,300 549.1 763.2
7,400 552.6 778.7
7,500 549 784
7,600 554 801.6
7,700 550.9 807.7
7,800 555.7 825.3
7,900 554.2 833.7
8,000 557.5 849.2
8,100 555.3 856.5
8,200 555.9 867.9
8,300 553.6 875
8,400 552.6 883.8
8,500 549.9 890
8,600 545.3 893
8,700 542.6 898.8
8,800 539 903.1
8,900 533.9 904.7
9,000 530.8 909.7
9,100 523.6 907.3
9,200 521.4 913.3
9,300 517.3 916.1
The official peak power number for this build is 916 horsepower at 9,300 rpm, but the SB2 is obviously capable of more. The problem is that while the land speed race team Dorton built this engine for does have the budget for big power; they don’t have enough scratch to recover from big “booms.” So Dorton set the redline at 9,300 to protect the valvesprings over a 5-plus mile top-speed run. Still, it is more than enough to hit 238 miles per hour, with possibly more under ideal track conditions.

Sources

ATI Performance Products
Baltimore, MD 21207
877-298-5039
www.atiracing.com
Aeromotive
Lenexa, KS 66214
913-647-7300
http://www.aeromotiveinc.com
Automotive Specialists
Concord, NC 28027
704-786-0187
www.automotivespecialists.com
Holley
Bowling Green, KY 42101
866-388-5120
www.Holley.com
Edelbrock
Torrance, CA 90503
310-781-2222
www.edelbrock.com

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