1970 factory configurations
LS6 Chevelle versus Hemi ’Cuda
The LS6 has the higher published horsepower figure: 450 versus 425 for the Hemi. That answers the rating question, but it does not settle a race. Production figures also need care: an engine-option total and a U.S.-market car count cover different populations.
Compare the factory figures
This comparison concerns the 1970 Chevrolet 454 LS6 and Plymouth 426 Hemi applications. It does not substitute a later Corvette LS6, a racing engine or a modified surviving car. The table follows Chevrolet's AMA engine sheet, printed page 4 (PDF page 131), its powertrain sheet, and Plymouth's revised brochure specification page.
| Specification | Chevelle LS6 | Hemi ’Cuda |
|---|---|---|
| Displacement | 454 cu in | 426 cu in |
| Horsepower @ RPM | 450 @ 5,600 | 425 @ 5,000 |
| Torque, lb-ft @ RPM | 500 @ 3,600 | 490 @ 4,000 |
| Compression ratio | 11.25:1 | 10.25:1 |
| Carburetion | One four-barrel | Two four-barrels |
The cited tables publish engine ratings without explicitly labeling a gross/net standard in these columns. Keep that limitation visible when comparing them with other years or modern measurements. Chevrolet also states its atmospheric correction conditions in the sheet's footnote. These pages do not establish an identical test setup for the two manufacturers. See gross versus net horsepower for why a universal conversion percentage is unreliable.
The badges describe different ordering choices
For Chevrolet, SS454 identifies the equipment package; LS6 identifies the optional engine. An SS454 badge alone does not distinguish LS6 from LS5. ChevelleStuff's option history explains that distinction and the required transmission choices. Plymouth's brochure lists the Hemi as optional on the ’Cuda. Neither name authenticates the equipment in a particular restored car.
Read the Chevelle LS6 profile and Hemi ’Cuda profile for their option, source and identification records. Original paperwork and matching vehicle evidence matter more than a modern listing's headline.
What the production counts mean
ChevelleStuff's option table reports 4,475 LS6 engine options and 8,773 Z15 SS454 packages. It does not supply an LS6 body-style breakdown. The larger package total cannot be substituted for LS6 production, and neither total establishes an LS6 convertible count.
Hemmings reports 666 Hemi ’Cudas for the U.S., including 14 convertibles. The resulting 652 hardtops is a subtraction, not a separately quoted factory subtotal. Do not relabel this U.S. figure as worldwide production.
These sources support distinct, qualified counts. Dividing one by the other would obscure their different scope; neither tells you how many cars survive today or how many retain their original engines.
Which was faster?
This evidence does not establish a winner. A useful performance comparison needs dated tests with transmission, axle ratio, tires, vehicle weight, modifications and test conditions. A peak power rating cannot supply those missing variables, and picking the quickest published run for each car would not create a controlled comparison.
For now, use the factory table to compare the advertised engines and the profiles to examine each car's evidence. The interactive comparison tool can line up catalog records; it does not turn them into a head-to-head road test.