SDPC 5.7 HEMI Dyno Tests Reveal Surprising Results
In recent years, different engine swaps have begun to catch on, other than the typical Chevy LS or LT. One of those is America’s other pushrod V8: The Gen III HEMI. And while bigger is better, like the 6.4-liter or 6.2-liter supercharged Hellcat engines, the 5.7-liter HEMI is still a great option for those on a tighter budget who are still looking for modern performance. The team at SDPC (Scoggin Dickey Parts Center) has been dyno-testing different HEMI crate engines and performance parts, and recently compared different intake manifolds during 5.7 HEMI dyno testing, receiving some surprising results.
SDPC, located in Lubbock, Texas, has been around for almost a century now. What started as a dealership in 1929, founded by A.L. Scoggin and J. Ray Dickey, has boomed to one of the highest volume parts departments and the largest Chevrolet Performance dealer in the world. While they’re best known for being a dominating force in moving Chevrolet crate engines, they also have a long history of selling aftermarket parts, including Ford Racing and Mopar Performance parts.
SDPC Expands Its Performance Reach
When Gordon Paden joined the team in 2019, he helped lead the way in expanding SDPC’s well-known GM performance reputation to the Gen III HEMI platform. Paden is no stranger to performance cars and trucks. He has a long history of gas and diesel tuning, and currently owns a slick black Charger powered by an SDPC Raceshop-built HEMI with a Whipple, consistently running deep in the 9s in the 1/4 mile.
When it came time to dyno test the 5.7 and 6.4 naturally aspirated HEMIs on SDPC’s in-house engine dyno, the team consisting of Paden, Dane Arnold, and Kurt Urban decided to test what changes, if any, benefited the smaller 5.7 HEMI when it came to intake manifold selection. We all know that the 5.7 truck intake is a poor performer and a swap to the 6.4 truck intake is a better choice, but what about the car intake manifolds?
Inside the 5.7 HEMI Test Engine
The 5.7 HEMI dyno test engine is an off-the-shelf crate engine direct from Mopar Performance, part number 68303088AC, that the SDPC Raceshop pulled from their own shelves in the warehouse. This is the same engine you find under the hood of an R/T Challenger with a manual transmission. For this test, the engine has no MDS, the cam phaser was locked out, Kooks long tube headers, and an SDPC Stage 3 camshaft was installed with 223 degrees of duration on the intake and 331 degrees of duration on the exhaust, 0.596 inches of lift on both, with a 111-degree lobe separation angle.
“After posting these results last year, I had a ton of people commenting and messaging me, stating that they had seen the same results on their cars when hot-swapping the intakes at the track.” Gordon Paden – SDPC
Dyno Results Challenge Common Rumors
With this combination, the little HEMI cranked out an impressive 497 horsepower at 6,300 rpm and 473 lb-ft of torque at 5,000 rpm. This is a big jump from the baseline run with the stock cam, which made 383 horsepower and 424 lb-ft of torque. The next step was to see what an intake manifold swap does to these already impressive numbers.
If the 5.7-liter trucks benefit from the 6.4 truck intake swap, the 6.4 car intake would certainly help during 5.7 HEMI dyno testing, right? Not so. Another round of dyno testing with the 6.4 car intake manifold showed a loss after 4,800 rpm, with only small gains low in the rev range. While this may sound surprising, the reason Paden wanted to test this combo is because of what he had already seen with other racers seeing disappointing results at the track with this intake manifold swap.
Additionally, further testing confirmed these findings during the 6.4-liter dyno testing. When the 5.7 intake was swapped onto the 6.4-liter HEMI during cam testing, the results remained similar, rather than showing a loss, reinforcing the same conclusions that the 5.7 car intake is a good intake in stock form. It just goes to show, the old adage that “bigger is better” may not always be the case.
