Actual HP numbers from vintage Mopar engines.

[BSB67]

But why would anyone OVERRATE?

To sell more cars.

 

[GrabberOrange69]

I know my 70 383/330 4bbl 70 Challenger was a dog compared to my 71 340/275 Cuda but on the other hand, the Cuda was faster than the road runners. It did have headers on it but everything else was stock.

The 340 was a hot ticket in small block land. Could easily devour lessor big blocks from the big 3.

 

[oldbee]

To put this thread to rest, my high school buddy had a'68 Satellite 383 auto; he always lost to my Bee. 5hp makes a difference sometimes. Reaction time,etc plays into it also.

 

[Bad B-rad]

To sell more cars.

Man, now that you say it, it seams obvious, LOL!!!

I would think that type of marketing would backfire, as soon as people with the underrated engines started to lose street battles to engines they should (on paper) beat.

 

[Bad B-rad]

To put this thread to rest, my high school buddy had a'68 Satellite 383 auto; he always lost to my Bee. 5hp makes a difference sometimes. Reaction time,etc plays into it also.

Only if the true ratting of the Satellite was 330, and the Bee 335.

We have seen they definitely played with the numbers on some engines, so how do we KNOW what ones are true and what ones are fudged a bit?

I suspect the Bee was true 335HP and the the Satellite had less.
Or the rpm that they ratted the HP was not peak.

 

[Bad B-rad]

So Chrysler rated the 383 Road Runner at 335HP,
Hot Rod mag got 338Hp from as close to stock as they could get:
https://www.hotrod.com/articles/mopp-0209-383-engine-restore/

 

[Bad B-rad]

It made 338HP
But only 394 Torque?
Down from claimed 420ft lbs, I wonder why?

 

[Bad B-rad]

Looks like Mopar was honest with the 383 RoadRunner engine.
but liars on the Hemi, and 340!!
Well with the Hemi, they just rated it below peak, but the 340,made about 320hp
and the 340 6 Pack made 356HP at 5,500rpm.
https://www.hotrod.com/articles/bad-mopars-340-beat-ford-chevy-shocking-new-data/

 

[Sixpactogo]

Only if the true ratting of the Satellite was 330, and the Bee 335.

We have seen they definitely played with the numbers on some engines, so how do we KNOW what ones are true and what ones are fudged a bit?

I suspect the Bee was true 335HP and the the Satellite had less.
Or the rpm that they ratted the HP was not peak.

From what I remember, the 5 hp was added because of the HP exhaust manifolds. Satellite would have had the log manifolds. Whether they actually verified it or guessed it, Who knows? Maybe the clutch fan and the HP exhaust combo added a couple ponies.

 

[Nate S]

A lot depends on what you really want. Ultimately, acceleration depends upon net torque to the rear wheels over time. Horsepower figures are almost exclusively “peak” which is just a little piece of the story, they are the part that’s focused on though.

If we say that modern horsepower numbers are pretty accurate we can use some of the commonly found formulas to show how that maps to quarter mile speed. A typical one is (.00426 x mph)^3 x weight = HP.

You can then take one of these cars when new as tested by a car magazine and calculate out the horsepower. So a 66 satellite with a 383 tested by car life did 91 in the quarter at 4160 lbs. that calculates out to 242 hp.

The very best Hemi cars in road tests hit 105 in the quarter. That calculates out to 372 HP at the same weight. A typical 440 magnum hit 99, that’s 312 hp. ‘64 426 wedge Fury 95.5, that’s 280. Roadrunner is about the same. Go find your favorite old road test and have fun.

This is a remarkably accurate way to judge actual factory hp back then. You can find formulas that are a bit different from .00426 but they are all pretty similar. You can also take modern cars and plug them in. You’ll find they are pretty close to advertised HP.

Also note how similar these are to the chart up above.

 

[Dibbons]

That horsepower formula in post #30 is for flywheel HP or rear wheel HP or other?
My 1965 273 Valiant four-door ran 108 MPH (12.72 best ET) at 3150# which works out to 306.66 HP. Sounds about right.

 

[SlinktRR]

I dyno'd a mostly stock rebuild 71 383 with a .484 purple cam. It had 324bhp, which is pretty close to the 300bhp rating from factory.

 

[Fran Blacker]

Couple of guys I knew raced each other. A 454/450hp Chevelle And a 340 Duster with Marsh (sp) soft compound tires. 454 got smoked no traction off the line, gave up at the 1/8 mile, cost him $50 this was 1970 money. Chevelle ran 12.8's at Ct dragway with 7" slicks.

 

[Nate S]

That horsepower formula in post #30 is for flywheel HP or rear wheel HP or other?
My 1965 273 Valiant four-door ran 108 MPH (12.72 best ET) at 3150# which works out to 306.66 HP. Sounds about right.

View attachment 978057 View attachment 978058

That would be rear wheel horsepower.

 

[Bad B-rad]

I was figuring that it must be CRANK HP.
Because I just had my wife use the hp calculator on my 2016 R/T (5.7)
Stock its factory rated at 370HP. I have 6.4 intake (SRV) and exhaust manifolds,with 6.4 cats, and a stock SRT catback exhaust, Mopar CAI, and custom tune for the added parts.
I had guessed (with out calculator) I was at 410-415.
and it came out to be 428HP

I think stock most 2016 5.7 are at 310-315RWHP

numbers I used was 106 MPH and 4800 lbs
runs 1/4 @ 12.9

 

[69Coronetrt]

From what I remember, the 5 hp was added because of the HP exhaust manifolds. Satellite would have had the log manifolds. Whether they actually verified it or guessed it, Who knows? Maybe the clutch fan and the HP exhaust combo added a couple ponies.

4bbl manifolds are 4bbl manifolds regardless of the model. There are 2bbl and 4bbl manifolds but no unique 383 HP manifolds. Meaning a 330 horse Satellite and a 335 horse Road Runner use the same manifold. The biggest difference between the two was the cam and valve train.

Regarding advertised HP ratings specifically the 335 horse rating in the Road Runner and Super Bee....

Consider the competition in the same category. Compare the CID and the horsepower ratings of the Ford 390 in the Fairlane and the Chevy 396 in the Chevelle. Also look at the rating for the 389 GTO, 400 Buick GS and Olds 442. Which manufacturer had the smallest CID? Which HP to CID looks 'the best'?

 

[Dibbons]

My only "street racing" was on a two-lane country road in my parents new '71 Road Runner 383 auto with 3.23 open rear and G60-15 Polyglas tires as a junior in high school. Beat my classmate's Mercury Cyclone 390 GT (rated 325 HP) by half a car length. Photo parent's Bahama Yellow Road Runner today:

 

[BSB67]

That would be rear wheel horsepower.

Actually, I don't think so. I think this, like other formula that I know more about, are net-actual flywheel hp (verses gross-corrected flywheel hp from an engine dyno). Net actual can look a lot like RWHP, depending on several factors.

 

[33 IMP]

Roger Huntington was a famous auto writer/tester from the sixties and seventies who did testing on the muscle cars of the day, using a fifth wheel I believe. He was sure many of the muscle cars of the day were under rated by rating their horsepower at a lower rpm than actual peak. His list of top 10 underrated were all bigblocks but he did have a number for 340 4bbl.
340 factory 275 @5000
Real 320 @ 5600
Unfortunately he didn't test the 340 sixpack.
Below are excerpts from his top ten list, rated first, then his calculated. ( the whole list is posted on fabo under the title " real horsepower of muscle cars" from 2010)
#8 440 magnum 375 @4600, 410 @5400
#4 440 6 pack 390 @ 4700, 430 @5600
#2 hemi 425 @5000, 470 @6000.
Number one was the L88/ZL1 (big surprise) and the list included just about every hipo big block from the big three.
To me, the most comical was the 390/428 cj from ford. The 390 was a complete dog, rated at 335hp, ruined by 396 chevelles, and destroyed by roadrunners. But the 428cj was rated at the exact same 335hp, and was very competitive with any but the very top tier of muscle car.

 

[Dibbons]

In 1984 I was a state traffic officer in Los Angeles driving an E48 Dodge Diplomat (318 four-barrel) which could not even merge on the freeway with traffic flow if the on-ramp was uphill. The same cars at the CHP Academy were quick (the mechanic at the academy had some tricks up his sleeve).
Per Allpar:
Most Diplomat 318 squads (including municipal cars) seem to have been fitted with a standard two-barrel carburetors, as well as the usual electrical, suspension, and transmission upgrades, for use as detective cars and low-performance patrol duty. The state police tended to favor the four-barrel carburetor, which added some horsepower but had about the same torque; Danny Moore reported that cars equipped with the 318 four-barrel had roller cams and 360 heads.

Police could also order a slant six model, useful in cities (where Motorola was more important than motorpower) and detective work, in some years. Slant six powered M-bodies could (in 1981) muster a 21 second 0-60 time, with a top speed of under 100 mph. Gas mileage was around 18 mpg, far higher than the 318 four-barrel V8s, which got around 14 - 15.5 combined city-highway miles per gallon.

The V8 models, with 318s and four barrel carbs, were doing 0-60 in around 12-13 seconds; 100 mph came up in around 40 seconds, with quarter mile times of around 19-20 seconds. (Times are from MSP tests.) The 318 four-barrel was rated at 165 hp and 240 lb-ft of torque.