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Actual HP numbers from vintage Mopar engines.

Bad B-rad

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In the most recent issue of Mopar Action, they have an article on the different types of engine dyno's. (engine/chassis/inertia)
And how some numbers advertised by Chrysler, were accurate, some were BS.
I will quote Richard Ehernberg from the article:

"The 1966 318 poly 2bbl was rated at 230hp @4,400rpm(which was close to valve float)
The 1965 273 4bbl has much higher compression, better heads, much more camshaft, a 480cfm AFB carb (topped with an unsilenced air cleaner) 2.50 inch straight through exhaust(not reverse flow) single plane manifold, and was perfectly happy at 6,000+rpm all day long. It was rated at 235hp @5,200rpm.
All things being equal(same car, same gears,etc) the 273 car would be in the next zip code while the poly 2bbl was wheezing along. 5 hp different, my ***"- Ehernberg

I know that was the authors opinion, but I am sure we have all heard, the 340, was WAY under rated, as was the 426 Hemi.

I have always wanted to find real engine dyno numbers for as delivered, engines, but I have only ever found ones on the 426 Hemi.

Another rating that I have ALWAYS been curious about was the 383 4bbl 330HP, and the 383 MAGNUM/Roadrunner engines at 335HP.
I know cam is different, and that power will come on at different rpm between the two, but 5 peak HP, IMO you could not even feel 5 hp, when installed in a car.

I have no experience, with driving or owning a 440 6BBl, but I was always interstead in the real numbers on that engine also, as I have read this was also underrated a bit. With the claimed reason being the real HP numbers came to close to the Hemi's rating

I will quote the article again:
"Countless other examples, one that comes to mind is the mid 60's 383 4bbl rated at 330 ponies @4,600rpm VS the 1968 Roadrunner 383's 335HP (@5200rpm) the 68 906 heads, vastly improved manifolding, AVS carb, and mainly a camshaft that was virtually full on race, next to mid 60's stuff. Yeah 5 hp."--Richard Ehrenberg

He goes on to offer some proof of the factory fudging with the HP numbers, by showing a chart from 1971 when Chrysler published both gross and net HP ratings,( engines were unchanged) and comparing the 318 vs the 340's numbers.
The 318 lost 33% of its HP rating from gross to net, but the 340(claimed to be underrated), only lost 9%
This looks to lend creditability toward the fact that the 340 WAS underrated.

I have seen videos from Nicks Garage, and he dyno's a stock 426 Hemi, I have seen a few stock 426 Hemi dyno videos, but never a 383 4bbl, vs 383 Roadrunner.
Even a video or 1/4 miles time slips of a 383 Roadrunner, vs a 383 Satellite(or similar weight car)

Has any major car mag ever done a test to see how accurately the ratings hold up?
Or any published chart of real HP number vs claimed HP?
I would be interstead in all of Mopars engines, from slant 6, to 6 pack.
Thanks.
 
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Here's your reference charts, they are Chrysler's own data.
 
The chart#2 is not Chrysler, but published by Clayton, for use with their dyno.

It also goes on to say how the Clayton dyno was not so good at reading HP, more a testing tool, to replicate road conditions, as this was one of the first chassis dyno.
 
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To make a comparison as close as possible, IMO we would have to use engine dyno numbers, not chassis, just to eliminate drive train loss.
I know every engine dyno would read differently, but it would be as close as we could probably ever get.
 
For '71 chart, the gross torque for a 340 and a 440 (low-performance) are both 410 at 3,400. Hard to believe that is accurate.

1971 340 per Allpar:

typo.png
 
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For '71 chart, the gross torque for a 340 and a 440 (low-performance) are both 410 at 3,400. Hard to believe that is accurate.
Also the 383 4bbl LO CR is at 410TQ, good catch Dibbons!!

I could be more of "fudging the numbers"
If you look the 440 HI-PO makes 480 @3200rpm
the 440 lo-po is 410@3400, generally, not always, but most of the time, the low-po offering make MORE torque then the hi-po at a LOWER rpm.


It could be the lo-po, did make more torque, but perhaps, it came on at 2600rpm, and by 3400 was falling way off peak??
Is so why would they rate it at that rpm? They MUST have a reason, maybe to upsell customers to the hi -po version??

All this just goes to show how valuable a real dyno of the stock spec engines, could be.
 
I know Chrysler under-rated HP numbers back in the late 60's / early 70's because of the insurance companies. Probably GM and Ford did the same. I don't know how much they were under-rated but one engine builder I used to know told me the 426 Hemi was rated at 425 hp but was closer to 465 from his testing. Quarter mile time slips were way more important to me. My driving record had more to do with my insurance rates than the R/T badge on my Charger so I never was too concerned with rated HP. It was just another set of numbers for bragging rights. Who knows how accurate any of them are these days. I have chatted with guys over the years that did a little porting on the heads and put on a high rise manifold and now somehow they have 650 hp. No dyno needed.
 
I suppose the numbers were accurate for the rpm stated. But what if you raise/lower the rpm?

IOW, suppose they advertise an engine's HP as 425 at 5200 rpm but if you continue to 6200 it's 450. Both numbers are accurate.
 
The 383 in my 66 Charger (300 HP) entirely stock was a strong runner. They were advertised at 10:1 but likely less than that.
I believe the factory numbers to be pretty accurate.
It was capable of getting rubber on a 1-2 shift at around 35 or 40 mph.
 
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.
 
70 383hp was 335. My cousin had a 70 Gran Coupe 383 with headers one of the fastest cars I've ever ridden in.
Not all factory engines are created equal.
 
For me its just a matter of wanting to know, to know the actual net HP number it made, and know why they rated at the rpm, they did, and so on.
Most of the time, at least today they rate an engine at PEAK HP and the rpm it made that number.

We all know peak number is not as important as an across the board number.
A engine that peaks at lets say 200hp, and has a torque curve like a upside down "V", is not as impressive, or fun to drive as one that makes 175 peak, but has a nice flat torque curve.
Finding out the true #'s also really wont change the past at all, but for me its about wanting to know, and learn about our Mopars.
Some guys love to know what options you could get with what engines on what cars, or how many of a certain model came in what color, or drive train option. (ie: 1 of 16)
Those things don't interest me as much as maybe they way Chrysler did some of the things they did, and WHY they did it.
 
I have heard a lot of people say that on the street a 440 would take a Hemi, but at the strip, the Hemi wins.
What is fast on the street, is sometimes different then fast in the 1/4.
When we used to mess around from stop light to light, we go 0-65 maybe 70, and then shut it down, no one wanted to get hurt, or hurt anybody, so we rarely took it to the speeds you can do at the drag strip.
 
The couple of engines that people say were underrated were probably close to accurate for corrected gross hp, and too high for corrected net hp. The factory hp numbers were were someplace between a little happy to really happy.

Either collect some magazine test data and plug it into your favorite hp calculator, or look up what Chrysler published as the "real" hp numbers.
 
I have heard a lot of people say that on the street a 440 would take a Hemi, but at the strip, the Hemi wins.
What is fast on the street, is sometimes different then fast in the 1/4.
When we used to mess around from stop light to light, we go 0-65 maybe 70, and then shut it down, no one wanted to get hurt, or hurt anybody, so we rarely took it to the speeds you can do at the drag strip.

When this condition exists, its normally due to traction/60 ft times, not horsepower.
 
I understand this, but it leads a lot of people to say one car is faster, then another.
And it may be faster, in one type of test, and not as fast in another.
Like car set up for 1/8, vs 1/4 mile.
That was the conditions that I was making reference to.
 
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GM did the same thing , the 396 L78 was rated in the corvette at 425hp, in the chevelle at 375hp.
only difference was in the corvette at 6400rpm, in the chevelle at 5600rpm, marketing purpose only
 
GM did the same thing , the 396 L78 was rated in the corvette at 425hp, in the chevelle at 375hp.
only difference was in the corvette at 6400rpm, in the chevelle at 5600rpm, marketing purpose only

That I can understand GM's reason, as the Corvette is suppose to be the top dog.
It has to have a little more then the everyday working man's car.
I think GM did the same thing in the 80's with the turbo Buick, and the IROC Z.

But why would anyone OVERRATE?
I can maybe understand the underrating, for insurance, or to "SNEAK" an engine by some sanctioning bodies.
 
GM did the same thing , the 396 L78 was rated in the corvette at 425hp, in the chevelle at 375hp.
only difference was in the corvette at 6400rpm, in the chevelle at 5600rpm, marketing purpose only


L78 Nova 4 speed. What a beautiful thing.
 
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