If nothing but the best will do for your Hemi buildup, look no further than the Wilson billet manifold.
Stock SRT8 vs Wilson Billet for a Modified 6.1L
Stock SRT8 Intake: 489 hp @ 6,200 rpm
Wilson Billet Intake: 510 hp @ 6,800 rpm
Largest Gains: 19 hp @ 6,500 rpm
The Wilson billet intake easily bettered the factory SRT8, and (unlike other designs) did so without any significant losses in low-speed power. What the Wilson intake needed was actually more engine.
Stock SRT8 vs Wilson Billet Intake for a Modified 6.1L
Stock SRT8 Intake: 453 ft-lbs @ 5,100 rpm
Wilson Billet Intake: 451 ft-lbs @ 5,100 rpm
Largest Gains: 16 ft-lbs @ 6,500 rpm
In terms of peak torque production, the two intakes were within 2 ft-lbs of each other; the Wilson design came on strong after the torque peak.
Test 6: Single-Plane vs Edelbrock Dual-Quad Intake for a Modified 5.7L
This test was as much about the intake manifold design as it was about the method of fuel delivery. In this test, we compared an Edelbrock Dual-Quad intake with a pair of carbs to a single-plane intake with a 4-hole, EFI throttle body. The test engine was your basic 5.7L Hemi equipped with the usual modifications. The Mopar Performance crate engine was augmented with a new cam and ported heads. The original cam provided with the crate engine was replaced by an XFI 273H-14 grind from Comp Cams. The healthy XFI cam offered a .547/.550 lift split, a 224/228-degree duration split and 114-degree LSA. The cam required the use of a set of 26918 beehive springs and 762 retainers to provide the necessary coil-bind clearance and RPM capability. The last thing you want is to limit the performance of your cam with valve float. To ensure adequate flow for the new power potential of the modified engine, the stock 5.7L heads were given the once over by the guys at Total Engine Airflow.
Having run it on a number of other occasions, we knew what to expect from the MP single-plane intake provided with the crate engine. The design offered plenty of peak power (479 hp at 6,900 rpm in this case), but often lacked torque production lower in the rev range. The peak torque production of 404 ft-lbs at 5,300 rpm only hinted at the limited mid-range power production, but it became much more evident after we installed the dual-quad intake from Edelbrock. Not just any dual-quad intake, Edelbrock designed a dual-plane, RPM Air Gap, dual-quad manifold for the late-model Hemis. The new intake was designed to accept a pair of 500-cfm Edelbrock Thunder Series AVS carburetors. As we have come to expect from their namesakes, the Air-Gap design promised plenty of performance by isolating the charge air from contact with the heated engine. The real key to the power production was the dual-plane design. After installation of the Edelbrock dual-quad Hemi intake and carbs on our test Hemi, the peak horsepower output dropped slightly compared to the racy single plane, but was still adequate at 463 hp at 6,600 rpm. The peak torque output jumped, however, to an impressive 420 ft-lbs of torque at 4,900 rpm. The dual-quad intake outperformed the single plane up to nearly 6,000. Now toss in the cool factor and you have some very compelling reasons to top your Hemi with a trick induction system.
All of the powerful original Hemis had multiple carburetors, so it was only natural for Edelbrock to design a dual-quad intake for the modern Hemi.
The dual quad improved power production compared to the single plane up to nearly 6,000 rpm, but the single plane pulled ahead slightly on the big end. For most dual-quad Hemi owners, they will appreciate the look and extra grunt offered by the dual-quad setup much more than any missing horsepower past 6,000 rpm.
Single-Plane vs Edelbrock Dual-Quad for a Modified 5.7L
MP Single-Plane Intake: 479 hp @ 6,900 rpm
Edelbrock Dual-Quad Intake: 463 hp @ 6,600 rpm
Largest Gains: 20 hp @ 6,900 rpm
The dual quad offered improved performance and horsepower production up to 5,900 rpm, but the single-plane MP intake pulled away thereafter. The short-runner single plane was designed to improve power production higher in the rev range, but nothing looks as cool as a dual-quad Hemi!
Single-Plane vs Edelbrock Dual-Quad for a Modified 5.7L
MP Single-Plane Intake: 404 ft-lbs @ 5,300 rpm
Edelbrock Dual-Quad Intake: 420 ft-lbs @ 4,900 rpm
Largest Gains: 24 ft-lbs @ 3,700 rpm
The dual-quad intake from Edelbrock more than looked the part. The design improved torque production by as much as 24 ft-lbs, with substantial gains up to 5,800 rpm. The additional torque offered below 6,000 rpm will be much more useful than the loss in power above that point.
Test 7: Mopar Performance Single-Plane vs Speedmaster Downdraft IR Intake for a Mild 5.7L Hemi
Right off the bat, we should stress that the individual-runner intakes looked so amazing that most Hemi enthusiasts will chose it over any other intake based on looks alone. Nothing screams “look at me” like a downdraft EFI system with eight massive butterflies and full-radiused, polished air horns. These intakes are, however, not for the faint of heart, as tuning them for use as a daily driver can be difficult and time consuming. It’s not impossible. Just be prepared to spend some time getting the thing to idle, take throttle, and drive down the road with civility. The WOT stuff is easy by comparison; there is never a shortage of airflow from one of these systems. Many enthusiasts think that the massive airflow potential of these individual-runner intakes is the reason they make so much power, but the reality (for this test) is runner length produces the power. The single-pane MP intake offered more than enough flow to satisfy the power needs, but just check out the power differences lower in the rev range as airflow is less critical. Power gains that occur through the entire rev range are generally a function of runner length.
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