How much horsepower did the....

[moparsinbarns]

How much hp did the 70 Cuda's 340, 383 and 440 have?

[Big Lebowski]

275 hp, 335 hp, 375hp

[Mike DC]

Big Lebowski's got the official hp ratings all nailed down.

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Off the record, the numbers often got distorted, though.  (They sometimes got inflated to help sell an engine or make it compare better against a competitors' model.  Or they sometimes got deflated to sell a higher-priced engine option or keep a racing rulebook from outlawing it.)

Here's some wild guesses for what the true numbers might have been (watch this thread derail now . . .):

340 magnum = maybe 320-330 hp? (It's an absolute screamer when you rev it up high enough.)

383 magnum = 330-340 hp  (But it feels like more than that. Way more low/midrange torque than the 340.)

440 magnum = 350 hp  (Most torque of all. Needed bigger heads though.)

[69_500]

Hmmm, so you think the factory over rated the 440? You think the 375 hp, is more than it was actually putting out? Or was that a typo Mike?

[Jon Smith]

  i think they were overrated, 440 cars were rated at 290hp in 72(SAE net) and they weren't really any slower than the earlier ones (faster in my limited experience of stock 440 cars)
to be honest i think everything except the 340s were overrated, i've seen an old dyno test of a new "335hp" 383 that made about 285

[Mike DC]

All those #s I posted above are assuming you ignore the factory's 5500-rpm redline, and just rev the motors until they get unreliable or the power peaks over.   

I say that about the stock 440 magnum because I've occasionally read about some Mopar engine bigwigs saying that.  My gut feeling is the same thing.  In dead-stock shape a 383 magnum will push a car almost as hard as a 440 magnum.

(Same principle that got the 426 Hemi stuck with a low official hp rating:  The "425 hp @ 5500 rpm" rating was technically true, but the engine's actual power peak was more like 525 @ 6700 rpm.)

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Assuming two engines both have the same cylinder heads, then theoretically a 4-liter engine @ 8000 RPM is burning the same amount of gas as an 8-liter engine @ 4000 RPM.  Of course the torque numbers of the 8-liter motor are gonna be a whole lot better, but the hp number is probably very similar.

Rev a smaller 383 up to 6500 rpm to stuff the heads as full as a 440 can do at 5500, and the HP number are gonna be close. 
(Yeah, I agree the 440 would win if you're comparing 5500-rpm readings on both motors, but the 383's power peak is higher up.  And I've seen the 383's stock valvetrain handle 6500 as long as everything's in working order.)

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All this is not to say that I think a 383 is truly "equal" to a 440 though. 
The 440's got more torque and more raw potential, you just need some Indy heads get ahold of it.

[moparsinbarns]

Thanks

[Big Lebowski]

It's all about compression, the early Max Wedge had it all at 13-1. '67 to '69 440 HP's were a good 10-1, 440 Six-pack was 10.50-1, but then came the smog reductions...'71 was 9-1, '72 was 8.5-1, then oh boy 8-1.

  The book says '67 383 2bbl. 335 HP, and the '72 440 Six-pack 290 HP.

[Mike DC]

         
Yeah, that's true too. 

The compression numbers on these motors were fluctuating.  They were usually rising in the mid-60s and then dropping in the early-mid 70s.  That really affects the final hp numbers.

       

[tan top]

in one of the mopar magazines they done a stock  build up on a 1970- 440 MAGNUM 4bbl , with cast hp manifolds and a factory blue print , a good few years ago  it only  made 350 HP  gross, compared to the advertised number of   375 HP gross. a former Chrysler technician who used to work in the dyno lab said the reasons the ratings differed was[ no power robbing accessories were connected plus we adjusted the ignition ,for total spark advance ] and the engines that were tested were loose . they did make that number, and some times more, plus it was something about the dynos were not  corrected to the same industry standard like todays dynos.  i don't think it was (gross or SAE nett)  it was about  automotive  rating standards that different dyno manufactures that take into account air pressure and temperature etc, on different days and calculate an average, so for example back in the day  in stead of a 440 making  X amount of HP at sea level and the the same engine making less power higher altetude the dyno's computer would adjust it to what ever rating  standard it was set  for by the manufacturer ,some thing like that i think.  there can be 50hp or more difference in todays dynos depending on what rating thay are corrected to ,i think  that includes chassis dynos , for me the only true dyno is the  T/S mph at the end of the 1/4 mile compared to the cars weight , thats just my

[Big Lebowski]

Yep, and back then gas was way higher octane, 90 something octane? A can of race gas can make anything run like a Hot Rod. My Charger gets the good stuff.

[cobradriver]

now my charger is equipt with the 383 2v,   so tell me what the diff between the magnum 383 4v, or 383 4v?....i have been told its all  about the heads....and all i needed to do was swap out the heads...kinda a bolt on deal....it has a after market holly 4v with a edelbrock intake...i cant wait to get my handsinto redoing this car....but it may have to wait till i get back from iraq......4th tour in my 17 years.....god i cant wait to retire....be the walmart greeter guy with the hot charger,.....lol

[71charger_fan]

Back in the day you used to see people talk about putting 440 heads on a 383. Even some car magazines fell into that trap. But, in reality, 383 heads and 440 heads from the same model year are the same piece. Most of the vendors in the magazines simply sell them by casting number. 906s, 452s, etc. Personally, for today's use, I think the 452 is a better choice than the 906 as the 452s generally came from the factory with hardened valve seats. I think you'll find most of the performance difference between a 383-2v and a 383 Magnum of the same year can be made up simply by switching to dual exhausts and a four barrel. That little carb and one narrow exhaust pipe really chokes those things.

[Ghoste]

Not in 1967. 

[cobradriver]

and that is pretty much what has happened to this car so far....it has a holly 750, with an edelbroke intake....the vacum advance unit on the distributor is really close to the intake....almost seems like its pinching the vacum line....what is a really good street intake carb set up on a 383?....just for the street...i want power but not gonna be running the strip....yet....hehehe

[OttawaCharger]

It was my understanding that the 383 2v (G code) had a lower compression than the 383 4v(h code) which also contributed to the HP difference. 

[71charger_fan]

I did say most, not all the difference.

There was an interview with a retired Chrysler dyno operator in one of the magazines years ago. What he said boiled down to the engines made what marketing told them to have them make. You certainly wouldn't want to overrate an engine. Not if your company had any hope of being competitive in NHRA stock class racing. See if you can find out what HP NHRA assigned to the various engines at the time. I believe their numbers were a little more real world. Didn't they refactor the 426 to 500hp?

[Vainglory, Esq.]

It's also possible that they used the "hemi test" on some of these engines.  They ran each hemi up to 425 horsepower and shut 'em off.  If they had gone higher in the RPM scale, each one of those engines would have rated higher.

[John_Kunkel]

Hmmm, so you think the factory over rated the 440? You think the 375 hp, is more than it was actually putting out? Or was that a typo Mike?

Back in the day, the insurance companies felt that these motors were actually underrated and adjusted the hp ratings accordingly. Cars were given an insurance code based on the hp/weight ratio using the corrected hp numbers and the 440HP came out over 400 hp; the Hemi close to 500 hp.

The difference in the various hp ratings comes about because of the different methods of measuring hp, prior to '72 the hp rating was gross hp but in '72 they went to the net hp rating which lowered the numbers considerably. Coincidently, '72 was the year for an across-the-board drop in compression ratios so the hp numbers took an even bigger hit.