Actual HP numbers from vintage Mopar engines.

[BSB67]

I have seen lots of cars pick up substantial e.t improvement from a converter or rear gear swap. The mph changes only slightly. And they didn't add one single horsepower to the engine.
In my personal experience, I have changed rear gear a few times and seen virtually no change in et, (kinda depends on the torque characteristics of the engine) but I did a converter swap that picked my car up from 6.50s to low 6.30s with no other change.

Bad, or low dollar converters will eat power and, if that is the case, it will show up on the mph.

 

[BSB67]

Bad-B-rad, For the three examples that you've given, there are very rational explanations for what you displayed in these previous post as evidence that calculators are not accurate. But frankly, I'm exhausted.

Yes, mph/hp calculator formula/tables are estimating tools derived from empirical evidence. It has its limitations, which are reasonably understood. When a dyno number is not BS, and the car is running correctly, the hp results between the dyno and mph/hp calculator is usually close, but more importantly, the relationship is very consistent. When you get dyno/calculator result for a car that doesn't follow these trends, it is not the calculator that's wrong.

Dynos are tools as well. Very complicated tools. Intentionally, or unintentionally, dynos can give dramatically different results from one to the next.

Pick your poison, but be sure to keep your eyes open.

Here is what Ma Mopar says.

 

[Bad B-rad]

We both have different views on the HP calculator(based on weight distance, and MPH) and that is fine with me.

It just hard to make sense of the fact that by inputting the data (weight and MPH)my 67 383, (2bbl Newport engine, with 4bbl intake)in a 1966 Charger has more power then a 1967 Hemi Charger.
The cars weight about the same, all are 727 autos, one with 3.23,mine was sure grip3.23, IDK if test car was SG or open, and the other was 4.10 sure grip.

67 charger 426 w/727, 3.23 rear [email protected], from Car Life mag 2/67
67 charger 426 w/ 727, 4.10 rear 14.20@103 , from Hi Performance Cars 3/67
66 Charger 383 w/727, 3.23 SG rear 14.2@98 from posts #75and 76

I had always figured it was because of traction, I had the better wider tires, then the test cars.
The stock 67 Hemi Chargers were on like 6.35 wide tires??

BSB67, I think you are a very knowledgeable guy, and from what I have seen, post good useful information.
I have tried to back up my posts with examples, and links to WHY I have come think the way I do on this subject.
But I don't think either one of us is gonna change the others mind, on this topic and I am perfectly fine with that. So I am gonna just let this one be, as you said, I too am exhausted , and much rather enjoy discussing ANY OTHER topic at this point!!!