TheHEMI.com

What were the race hemi engines rated at? street hemi was 425 with 10.5 CR.

No actual figures were ever published, just estimates from all over the place. 500-650-800HP ranges with extensive modification.

Were the race HEMIs, like what came in the '68 Super Stockers,
really much different than a street HEMI? I think they came with
higher compression and a better intake manifold. Maybe they've
got better carbs? Seems like it wouldn't have been a huge bump
over a street HEMI, but on the other hand, who was going to buy
a race HEMI and keep it "stock"?

scottm wrote:Were the race HEMIs, like what came in the '68 Super Stockers,
really much different than a street HEMI? I think they came with
higher compression and a better intake manifold. Maybe they've
got better carbs? Seems like it wouldn't have been a huge bump
over a street HEMI, but on the other hand, who was going to buy
a race HEMI and keep it "stock"?

1964 and 1965 were the factory produced true "race only hemi cars".

Chrysler detuned and mass produced the hemi after that to get the production numbers up so they would remain "super stock" legal.

The race hemi had 12.5-1 CR, street hemi 10.5-1 CR. race hemi had a much more radical cam, different intake, and had headers. Surely this would have bumped the HP up a lot.

The race hemi was rated at 425 horsepower, the same as the street hemi. However, the race hemi's horsepower was grossly underrated. There were a lot of differences between the race hemi and the street hemi, and a significant difference in horsepower output. The major differences were compression ratio, camshaft, intake manifold, exhaust manifold and carburetion. According to the drag racers of that era, the factory super stock race hemis "in race trim" made 550 to 580 horsepower at the crankshaft. I know there was a big difference in how the race hemis ran bone stock and after being "race tuned." I saw two brand new super stock race hemi Plymouths run in Tulsa in 1964. They ran low 12s right from the factory. A few weeks later they were running mid to low 11s. That was probably the result of both chassis and engine tweaking. The major limiting factor was that the rear tires were limited to a maximum seven-inch tread width in the stock classes. Stock street hemis typically turned in the mid to low 13-second range in that era (on the same 7-inch tread width tires), which is convincing evidence that there was a substantial power difference between the race hemi and the street hemi.