Old horsepower vs New horsepower rating? - Chevelle Tech
Chevelle Tech join team chevelle as a supporting member  
Chevelle Parts at SS396.com      
GROUND UP & SS396.com         
Official Sponsor of Team Chevelle
     

Auto Insurance

Chevelles.com is the premier Chevrolet Chevelle Forum on the internet. Registered Users do not see the above ads.
Bench Racing Stories, cruising and more.

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old Jun 25th, 06, 10:57 PM
Aaron Aaron is online now
Lifetime Premium Member
 
Join Date: Oct 1998
Location: Florida
Posts: 6,715
Default Old horsepower vs New horsepower rating?

Was watching American Muscle Car this morning and they mentioned how the 426 Cuda was rated at 425 hp while it really was more like 500 hp.

The 396 was traditional a 325/350/375 horse deal. What was there acutual horsepower?

How does this relate to the 454 crate motors now that say 425 horses or the zz4 which proclaims 355 horses?

What is the major difference in determining horsepower.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old Jun 25th, 06, 11:25 PM
Junkyard Dawg Junkyard Dawg is offline
Senior Tech Team
Dave
 
Join Date: Mar 2004
Location: western Missouri
Posts: 5,949
Default Re: Old horsepower vs New horsepower rating?

Quote:
Originally Posted by Aaron
The 396 was traditional a 325/350/375 horse deal. What was there acutual horsepower?

How does this relate to the 454 crate motors now that say 425 horses or the zz4 which proclaims 355 horses?

What is the major difference in determining horsepower.
Would also like to know......
__________________
'71 Malibu 402 big block/TH350 trans - Sold 2 Jan '08
How to tell if your car is a true SS or not:http://www.chevelles.com/shop/ss_ident.html
Reply With Quote Quick reply to this message
  #3  
Old Jun 25th, 06, 11:38 PM
Thad Thad is offline
Senior Tech Team
Huh, what ?
 
Join Date: Jan 2000
Location: Patton PA.
Posts: 1,326
Default Re: Old horsepower vs New horsepower rating?

My take on it the Hemi may have been rated at lower than its peak power to get a softer class in the NHRA, or to fool the insurance companies, or that 500 hp is bullstuff and it really did only make 425 hp. Most stock hemis only ran low 13s anyway.

I do understand that between 1971 and 72 they changed from "gross" to "net" horsepower. My understanding is that gross may have been with headers and no accessories (water pump, alternator, fan) and net was with all the engine driven accessories in place and stock exhaust manifolds. Bottom line that with no changes to the engine itself power ratings dropped about 80 hp. More for some engines less for others.

Not sure how the current crate engines are rated, but a fellow TCer was running bottom 12s with a stock ZZ-454 in a 67 last fall. So I'd be inclined to believe that it was making at least the advertised 440 hp. My 72 with a stock ZZ 502 ran low 12s and I believe it long overdue for a tune. So I think the 502 hp claim is at least legit.

Oh and if you look up the spec.s the same 375 hp 396 in a Chevelle was rated at 425 in a Corvette with the only difference being the exhaust manifolds. Line up a 375 hp 396 and a 350 hp 396 and I'd bet the difference at the finish line indicates more than a 25 hp difference.
__________________
Originally Posted by Bertrand_Russell
One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision.
Reply With Quote Quick reply to this message
  #4  
Old Jun 25th, 06, 11:50 PM
-SS454- -SS454- is offline
Senior Tech Team
Chris
 
Join Date: Aug 2002
Location: Alberta, Canada
Posts: 3,586
Default Re: Old horsepower vs New horsepower rating?

There was a big thing with the insurance companies that if you made more than 1 hp per cubic inch, the costs went up. Which is why you often see power figures that are very close to the cubic inches, but not over.

Another huge difference is gross and net horsepower, net being power with accessories. I think one of the biggest factors, is its just a number rating. Numbers sell.

Despite the belief that the old engines were all these drastically underrated, super monsterous 600 hp engines, they often not nearly as powerful as people believe. Like the Hemi being 500 hp, well I seen a factory dyno sheet on the 426 Hemi, and it made 433 hp, and I think 466 ft-lbs, and I think that was with headers. ZL1 427, ppl think its 600 hp, stock it didnt even come up to 500 hp, after headers (no exhaust), and tuning and stuff, it made 523 hp. 100% bone stock when you put it in the real world, the factory ratings quite a bit off, and they dont make the power as one would expect due to the SAE net standards.
Reply With Quote Quick reply to this message
  #5  
Old Jun 26th, 06, 12:14 AM
Bomber '67 Bomber '67 is offline
Senior Tech Team
 
Join Date: Jan 2000
Location: Garden Grove, CA, U.S.A.
Posts: 3,543
Default Re: Old horsepower vs New horsepower rating?

Ahh yes, another one of those urban musclecar legends that will not die - but it does sound good!

One thing that is well known is that the "Gross Horsepower" ratings of engines back then was fairly bogus. Maybe the street hemi was less bogus than some others, but word on the street was that the hemi could be beat by all manner of lesser motored musclecars. The hemi certainly had a lot of potential, but in as delivered form the actual performance did not measure up to those 500 horsepower claims.

Thomas
__________________
El Caminos a pair: '67 Bomber, '65 496
Avanti, Corvette and more
Reply With Quote Quick reply to this message
  #6  
Old Jun 26th, 06, 4:47 AM
Q-ship Q-ship is offline
Tech Team
Karl
 
Join Date: Mar 2002
Location: Largo.FL
Posts: 954
Default Re: Old horsepower vs New horsepower rating?

I just got through reading in the Auto Math book by John Lawlor the Hemi was underated but only because they didn't do the math for Horsepower above 5000 rpm when that engine clearly still made torque above that rpm. He showed that the true Hp peak is 6000 and there using Chrysler torque numbers it made 470 hp @ 6000. By the way most all the manufactures did this at one time or another, it is just that most want to believe the numbers are way higher than they really were. The Hemi with headers and a good tune probably did make the magic 500 or damn close, just like the ZL-1 and the LS-6. I mean come on does anyone really believe that the differnet 455's from all the other GM guys only made 350 to 370 hp when they made 500 to 510 lbft of torque, these engines were more likely in the 390 to 420 range.
__________________
Life's journey is not about arriving at the gate well preserved, it's about skidding in sideways, all used up and worn out yelling........GOD, what a ride!!!!

Where patience fails, force prevails

Stapp's Ironical Paradox "The universal aptitude for ineptitude makes any human accomplishment an incredible miracle."
Reply With Quote Quick reply to this message
  #7  
Old Jun 26th, 06, 9:34 AM
pdq67 pdq67 is offline
Guest
Paul
 
Join Date: Jan 2001
Location: Columbia, MO, USA
Posts: 14,685
Smile Re: Old horsepower vs New horsepower rating?

I have a REALLY old mag somewhere that gathered up all this info and they came to the conclusion that a 375&425hp/396 was actually right at 410hp.

As for the bad-boy motors, it was where they ran the numbers. Like the 12.5 to 1 CR. L-88 was only 430hp vs the 11 to 1 CR. tri-power equipped, 435hp/427.

They dropped back on the rpm to pull this one off is all.

And one way under-rated motor was the Ford 428 CJ at 335hp or some such low hp number!!

I think the article said that Olds did get their "W" motors about right-on if I recall right for back then...

pdq67

Last edited by pdq67; Jun 26th, 06 at 9:50 PM.
Reply With Quote Quick reply to this message
  #8  
Old Jun 26th, 06, 10:08 AM
pop d top pop d top is offline
Tech Team
 
Join Date: Dec 2003
Location: Las Vegas, NV
Posts: 443
Default Re: Old horsepower vs New horsepower rating?

Quote:
Originally Posted by pdq67
...As for the bad-boy motors, it was where they ran the numbers. Like the 12.5 to 1 CR. L-88 was only 430hp vs the 11 to 1 CR. trip 425hp/427.

They dropped back on the rpm to pull this one off is all...pdq67
I'd read in one of my Vette history books that the L88 was deliberately advertised at 430 to discourage street driving yokels from buying it...the pitch would go something like, "It's only 430 HP you have to use racing gas and it's only got one 4bbl carburetor. You can buy this 435 horse TRIPOWER 427 for much less, use just premium fuel and have 5 horses more for less money, and less hassle! And look how good that triangle shaped aircleaner looks. C'mon, more horses, less money you want the tripower right?" Real gearheads knew the difference but your average car nut would look at the numbers scratch their head and buy the tripower. Chevy only wanted REAL racers to buy the engine so they wouldn't have the service/warranty problems they knew a street driven L88 would give them.
__________________
SKIP (Pop D Top)

'69 El Camino (for my daughter)
'69 Camaro convertible (for me)
'67 Sting Ray coupe (for fun)
'70 Concourse Wagon-to be 2 doored (just cuz)
Reply With Quote Quick reply to this message
  #9  
Old Jun 26th, 06, 3:36 PM
Rowdy Rowdy is offline
Team Member
Vegas TC Ambassador
 
Join Date: Feb 2005
Location: Las Vegas, Nv.
Posts: 3,279
Default Re: Old horsepower vs New horsepower rating?

I was always led to believe that the early horsepower ratings were at the crank, while '71 and later ratings were from the rear wheels. Makes sense to me when defined as "gross" and "net".
Reply With Quote Quick reply to this message
  #10  
Old Jun 26th, 06, 4:21 PM
-SS454- -SS454- is offline
Senior Tech Team
Chris
 
Join Date: Aug 2002
Location: Alberta, Canada
Posts: 3,586
Default Re: Old horsepower vs New horsepower rating?

net isnt at the wheels. Its at the crack, its just with accessories (fans, alternator, etc). Not sure if it includes full exhaust though, I dont think it does.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply
Chevelle Tech > Information Exchange > Bench Racing      Current Topic: Old horsepower vs New horsepower rating?
Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Horsepower and road-racing... Derek69SS Pro Touring 25 Apr 19th, 06 8:36 PM
396 horsepower rating? bradford Engine 5 Apr 17th, 06 9:37 AM
Horsepower per Dollar ratio..... red68chevL Bench Racing 6 Sep 28th, 05 7:22 PM
Horsepower ratings in 1966 bobstarap Performance 10 Feb 1st, 05 8:56 PM
Diesel Fuel octane rating dwebb210 2001 31 Oct 17th, 01 10:13 PM


All times are GMT -4. The time now is 10:36 PM.


Is there a site like this for?    El Caminos Camaros Novas Impalas GTO Chevy Punch All Chevys

2009 Team Chevelle - AutoForums