Chatting with my Dad....

[Bluemonster71RT]

My Dad and I were chatting about horsepower ratings from back in the 60-70's and how the manufactures under rated a lot of the numbers for insurances reasons and what not. I asked if the engineers used dynos or did they just math it? I suppose they did an extreme amount of number calculations as computers were not yet a huge factor. Someone here must have some insight to this.  When they built these engines for production, did they have accurate dynos or did they do most of it by number crunching and maybe thats why the numbers they reported were off, because they were merely averages? 

[Chryco Psycho]

They used dynos but like anything a dyno reading can be tweaked , , I use Mustang dynos typically as they are the most accurate & repeatable but they are heartbreakers reading 15% lower than a dynojet for example !
There were also 3 ways of measuring Hp , in 70 it was gross , so the engine was running Nothing , they had external water  pumps to circulate water , not Alternator , power steering etc .
in 72 they went to SAE Net hp which was representative of as installed in the car with all of the draw from water pump , power steering , alt etc .
The Mustang & many other dynos read RWHp which is measured on roller at the tires so after all drivetrain losses are included , so making 400 RWHp is huge power = to close to 700 gross hp .
Reading can also be altered by temp & altitude corrections .
The bottom line is which # is "real" ?? I can tell you 400 RWHp on a Mustang dyno  is a massive improvement over factory HP 

[Bluemonster71RT]

Excellent info! Thanks. That must of been exciting times making those engines when they were new(ish) and that HP battle was on.

[Chryco Psycho]

Still is exciting times , I love to use today Tech & make these engines better than they ever were !
It is my ongoing passion to get as much as possible from any engine I build , I have built numerous engine now with 700+ gross HP & 750 + gross tq & still able to get 17+ MPG from them , I hate to leave anything on the table right down to 50 HP loss using a Carter / Eddy carb vs Quick Fuel / Proform & custom grind cams  , if you are paying for power why throw any away . Many people here can tell you how much differently an engine performs using the wrong or right cam !

[jimynick]

Excellent info! Thanks. That must of been exciting times making those engines when they were new(ish) and that HP battle was on.

They were, and that was with us looking in at it. There's some old Hot Rod mags where they featured factory experimental engines and the engineers sure had fun. Check them out as they ran the gamut from Chev hemis to DOHC heads and beyond. They knew what they were doing for the day. 

[Bluemonster71RT]

 I know its still exciting today but the 50's - 70's I think was the summit of what was possible for the technology that was had. If the emissions and insurance issues never happened, I could only imagine 1000hp street cars back then. Where would it of stopped? Noooooo seat belts lol.
Now it can be simulated so much easier and there is a real solid chance that engines will perform as calculated. Sometimes results can be a case of instant gratification. I just and fascinated with all the manual work done to maximize and control explosions for power and efficiency. As well as I am thrilled that even a 4 cylinder engine can put out over 300hp today. That is because of the data of yesterday being fully worked. We have 1000hp street cars now too, with lots of safety features. Never thought that would happen.