Hemi Horsepower

[Kevin68N71]

I was just watching a new episode of American Muscle Car.  They took some of the most popular engines--but not the exotic ones--of the musclecar era and put them on an engine dyno to see what they would do. 421 Pontiac, 409 Chevy, 427 Ford, etc.

All of them met or exceeded their horsepower ratings.

Now, I know the hemi was always underrated at 425hp for insurance reasons, but when they tested it, it got
820 HP!

This was on a non-modified, completely stock engine.  GEEZ!  I had never heard that or imagined.  I thought maybe they put out 600hp.  Is this right?  Can this be right?!

I wonder what the real HP of my 440 is.

[bordin34]

I have heard that the Hemi they used was a ringer.

[Kevin68N71]

You might be right.  I always thought that about 800hp would get your front wheels up in the air, and a street hemi stock in say a Road Runner is not going to do that.

What got me into muscle cars in the first place was a ride in a primer and purple 1969 Hemi Super Bee, stock, with a 4 speed.  We went flat out on Colorado Blvd in Denver through the gears.  The horizon definitely was dipping below the hood but we were not wheel standing!  Incredible power, but I don't think anywhere near 800hp.

Again, 600-650 sounds right...come on guys, I know there are some guys with Hemis on here, and have dynoed them for sure.

Please share...

[firefighter3931]

That motor was definately a ringer.  The best SS hemi builds make that kind of HP and run 70 grand to build....Barton, Macallum and several others are the big players in that arena.

True world numbers for a bluprinted factory spec '70 vintage 426 hemi is around 460-465 hp with a dead nuts tune on it. 

The Hemi was/is a great race motor but an average street motor in it's detuned state...that's the reality whether folks choose to accept it or not. 



Ron

[HKCharger]

is the 440-6 a better street motor stock vs. stock hemi?

[Kevin68N71]

Some people will say a 440-6 is better as its only a tick slower than the hemi but stays in tune much better.  Further, its cheaper.  OF course, that is for the street, the hemi goes much further in terms of what you can build.

I am surprised at the 465 number though.  To me, that indeed seems low.

Of course, a nice 440-4bl with a/c has a nice ring to it too.  Plenty of power and you're not sweating to death.

[69fuchs]

Hemis have a bad reputation caused by brain dead people that couldn't tune a lawn mower,  let alone a detuned race engine.

  My car runs just fine with the tune I gave it 10 years ago (including seven of eight spark plugs).  It is a 1970 engine with a stock hyd cam.  This engine has the same deck surfaces, line bore, rotating assembly,  cylinder head cc and porting that it was born with 38 years ago. 

So what is the number?  380 hp at the rear wheels, 470 at the flywheel. 

It runs 12.82@107 on the dragstrip and it weighs 4080 #

This is through the exhaust manifolds and 2-1/4" tail pipes.

[sick dawg]

my 472 crate hemi is rated at 525, but when it was fired up for break in on the machine it turned out 610 at the flywheel. Big surprise.

[Kevin68N71]

Hemis have a bad reputation caused by brain dead people that couldn't tune a lawn mower,  let alone a detuned race engine.

  My car runs just fine with the tune I gave it 10 years ago (including seven of eight spark plugs).  It is a 1970 engine with a stock hyd cam.  This engine has the same deck surfaces, line bore, rotating assembly,  cylinder head cc and porting that it was born with 38 years ago. 

So what is the number?  380 hp at the rear wheels, 470 at the flywheel. 

It runs 12.82@107 on the dragstrip and it weighs 4080 #

This is through the exhaust manifolds and 2-1/4" tail pipes.

You know, this is about the fifth time that I know of that American Muscle Car has stated BS.  I am about to stop watching.

That said, I am surprised at only 470hp.

For YEARS I have heard how "grossly underrated" in horsepower the hemi engine was.  According to your performance figures, the rated 425hp of the engine is only 10% off your horsepower as observed.  That is not grossly underrated.

If that is the case, why have we heard this all these years?  They always said it was for insurance purposes.  I can't believe there would be a significant difference between 425hp and 470hp.

[mikesbbody]

That motor was definately a ringer.  The best SS hemi builds make that kind of HP and run 70 grand to build....Barton, Macallum and several others are the big players in that arena.

True world numbers for a bluprinted factory spec '70 vintage 426 hemi is around 460-465 hp with a dead nuts tune on it. 

The Hemi was/is a great race motor but an average street motor in it's detuned state...that's the reality whether folks choose to accept it or not. 
I agree with ron but i cant comment on the hemi since ive never own one  :icon_smile_dissapprove:ed the 440 was considered a more street friendly motor (less tuning required etc) but would i take a hemi over a 440? in a heart beat! also, kevin "just" 470 h.p is alot from a unstroked stock motor ever notice how ford and gm rated their H.P at alot higher rpm's than mopar did...


Ron

[firefighter3931]

is the 440-6 a better street motor stock vs. stock hemi?

I'd say it is....easier to tune and stays  in tune. Better low end throttle response and overall drivability.

You know, this is about the fifth time that I know of that American Muscle Car has stated BS. I am about to stop watching.

That said, I am surprised at only 470hp.

For YEARS I have heard how "grossly underrated" in horsepower the hemi engine was. According to your performance figures, the rated 425hp of the engine is only 10% off your horsepower as observed. That is not grossly underrated.

If that is the case, why have we heard this all these years? They always said it was for insurance purposes. I can't believe there would be a significant difference between 425hp and 470hp.

American horsepower is just a TV show....you don't believe everything you see on the tube do you ? 

Sure the HP was undervalued a bit....for insurance purposes of course. 

The stock hemi cam is quite conservative so with a cam swap and some descent tuning the 426 was indeed capable of better performance. 

Hemis have a bad reputation caused by brain dead people that couldn't tune a lawn mower, let alone a detuned race engine.

My car runs just fine with the tune I gave it 10 years ago (including seven of eight spark plugs). It is a 1970 engine with a stock hyd cam. This engine has the same deck surfaces, line bore, rotating assembly, cylinder head cc and porting that it was born with 38 years ago.

So what is the number? 380 hp at the rear wheels, 470 at the flywheel.

It runs 12.82@107 on the dragstrip and it weighs 4080 #

This is through the exhaust manifolds and 2-1/4" tail pipes.

Aaron, i've said this before ; your car is an extremely well tuned combination and Kudos are well deserved 

As good as yours runs even you would have to agree it is not typical of the average street hemi. 




Ron

[firefighter3931]

So what is the number?  380 hp at the rear wheels, 470 at the flywheel. 

It runs 12.82@107 on the dragstrip and it weighs 4080 #

This is through the exhaust manifolds and 2-1/4" tail pipes.

I just ran the numbers using the Moroso slide rule. 107 mph @ 4100 race weight = 380 rwhp

380 rwhp + 15% drive line loss (std trans) = 447 flywheel horsepower.

So, there you have it....it is what it is. A very good running and well tuned street hemi 



Ron

[69fuchs]

Ron, the car has a slushbox with a stock hemi converter......not quite as efficient as a stick shift.

I got the flywheel numbers from virtual engine dyno

http://www.virtualengine2000.com/index.htm

[firefighter3931]

Ron, the car has a slushbox with a stock hemi converter......not quite as efficient as a stick shift.

I got the flywheel numbers from virtual engine dyno

http://www.virtualengine2000.com/index.htm

Oops, my bad   ....for some reason i was thinking your car was a stick. 

In that case ; 380hp + 20% = 475 hp

I've seen quite a few 426 "stock spec" type builds show anywhere from 450-465 crank horsepower....different dynos & different operators will skew the results somewhat, of course.

I'd say that yours is better than average....impressive actually, for an untouched 40 year old factory built engine. 



Ron

[Rolling_Thunder]

is the 440-6 a better street motor stock vs. stock hemi?

I think the 440+6 is a better street engine

[charger_fan_4ever]

I was just watching a new episode of American Muscle Car.  They took some of the most popular engines--but not the exotic ones--of the musclecar era and put them on an engine dyno to see what they would do. 421 Pontiac, 409 Chevy, 427 Ford, etc.

All of them met or exceeded their horsepower ratings.

Now, I know the hemi was always underrated at 425hp for insurance reasons, but when they tested it, it got
820 HP!

This was on a non-modified, completely stock engine.  GEEZ!  I had never heard that or imagined.  I thought maybe they put out 600hp.  Is this right?  Can this be right?!

I wonder what the real HP of my 440 is.

Its all about the dyno operator. Have 2 different guys run the dyno and you will see 2 different sets of #'s. Track times don't lie

Most of those magazine articles and shows probably tell the operator what they want to see on the sheet. If you notice some mag's always go to the same dyno operator.

[zerfetzen]

Didn't Chebie's 1970 454 get rated at 450hp, and wasn't that underrated?  This would mean that the stock 454 and Hemi are close, or that the 454 put out more power?  That can't be right.

I am anything but a Hemi expert, always been a 440 fan, but didn't it go something like this?

Hemi: Rated 425hp
Actually produced 500hp
Finely tuned (timing, carb, etc.) got 600-650hp.

I'm probably wrong, but thought I've read that a few times over the years.  Just chipping in my 

[zerfetzen]

I was just thinking (like I said before, definitely no hemi expert here) that I heard before that a Hemi could handle tons of advance timing compared to other motors.  If we couple that with how leaded gas back in the day wouldn't detonate like modern crap gas because it had a lot higher octane, the stock Hemi could be advanced quite a bit, then tuned appropriately there.  That's just a guess.

[Kevin68N71]

I was just thinking (like I said before, definitely no hemi expert here) that I heard before that a Hemi could handle tons of advance timing compared to other motors.  If we couple that with how leaded gas back in the day wouldn't detonate like modern crap gas because it had a lot higher octane, the stock Hemi could be advanced quite a bit, then tuned appropriately there.  That's just a guess.

Zerfetzen, your numbers are kind of along the lines of what I always thought.

Again, since when is 10% "seriously underrated" as I have heard and read for 30 years about this engine?!?!

[last426]

is the 440-6 a better street motor stock vs. stock hemi?

Several folks replied that the 426 is harder to keep in tune.  I just don't get it.  My 3rd generation with hydraulic tappets and, as all, mechanical secondaries, stays rock steady.  On the contrary, I would think that vacuum secondaries are more variable.  And both hemi and 6 bbl had dual points so they are even in that respect. 

In my first 71, a 440, I used to street race against a green superbird 6 bbl (this was around 1972-3). My 4bbl would win maybe half the time.  I don't race my hemi, but it sure seems faster than both of those cars.  But I now am at sea level and before was in Reno at 4500 feet.  you can see both cars at my website, http://www.marlia.com/charger/index.html. Kim

[firefighter3931]

Track times don't lie

Truer words were never said ! 

Most of those magazine articles and shows probably tell the operator what they want to see on the sheet. If you notice some mag's always go to the same dyno operator.

The dyno at Westech in California is noted for being a "happy" dyno....that's the one that Mopar Muscle uses in all  their magazine buildups. I've yet to see one of those builds thrown into a car and thrashed at the track to see if the (dyno) numbers are consistent with real world experience. 

Hemi: Rated 425hp
Actually produced 500hp
Finely tuned (timing, carb, etc.) got 600-650hp.

I'm probably wrong, but thought I've read that a few times over the years. Just chipping in my

The rated number would be correct....that's what the factory says they made. The 500hp number is off and the 1/4 mile ET's and trap speeds bear this out.


The race hemis with 12.5-13 :1 compression, big solid cam and Holley carbs were probably in the 580-600hp range. The mid-low 10sec ET's in a lightweight 68 Dart/Barracuda factory race car back up those numbers.




Ron

[charger_fan_4ever]

West tech

That was the dyno shop i was looking for. Thanks Ron

Totally agree with what you said about the race hemis in the dart/barracuda. For a 3000lbs car you need around 550-600fwhp to go mid to low 10's.

I've been in the drag world with a foxbody mustang for the past 4 years. Dunno how many times i heard guys say their 350 chev put out 500hp and had the sheets blah blah, but could barely pull off a high 12 on a dead hook in a 3000lbs cars.

Love to have seen what that claimed 800 hp hemi would run.

I have seen a pick up of 35hp with an additional 8 deg timing and more fuel pressure. I've always heard that the stock Hemi's were not well tuned.

Since they don't have a fp regulator other than timing what do they "tune" I assume the carter carb? I'm clueless when it comes to anything other than a holley or demon.

[Mefirst]

The race hemis with 12.5-13 :1 compression, big solid cam and Holley carbs were probably in the 580-600hp range. The mid-low 10sec ET's in a lightweight 68 Dart/Barracuda factory race car back up those numbers.

Ron

I don't think one can really compare the "Race" Hemis with the "Street" Hemis, then again the "Street" Hemi was a detuned "Race" Hemi, so the street version was more or less handicapped, and thats why it got beat by the 440 Six-Pack

Id like to see a comparison between a 426 Hemi (street) and a 440 Six-Pack where both engines are blueprinted and tuned to absolute perfection using ONLY stock parts, no exotic after market parts, then place both engines in the same car and see which one would be the best power dynamo...

/Tom

[max]

in a mopar artical several years ago Tom Hoover was asked what a street Hemis true HP was and he said that if everything was right it would be around 470-475 and the race Hemi was around the 540-550 range.

if you look at the new 426 crate Hemi it is listed as a supposely dyno proven 465 HP engine with the so called 9.1 compression which is about what the stock 1966-1971 Hemi engines had except they claimed 10.25 back then and the crate engine is using a dual plane single 4 bbl carb.

so if you were to take a crate engine which is basically a stock built 1966-1971 Hemi and just bolt on a 2x4 intake then there would be your 470-475 HP as Tom Hoover described and his artical was printed a good while before the 426 create engine was built.

there was alot of muscle car engines that were under rated in HP. just look at the advertised HP and the RPM range it was under. most of the RPM ranges were around the 4k mark and the engine still had more RPM range left in it.

i think in one artical i read claimed the stock 440 4bbl should have been rated at 410 instead of 375 and the 6 pack version should have been 430 instead of 390. coarse the 340 was the one that was truely under rated. the claim for a 340 4bbl was 270 HP and the later articals i have read showed a stock built 340 4bbl pulled 325 HP.

but again dynos can be very happy so it's hard to say if those #'s above were on happy dynos.

[Mike DC]

In regards to the "stock" Hemi hp number,


I've read at one time or another that the 425hp number actually WAS the real number - at 5500 rpm or whatever they quoted it. 

The factory's deception was that the motor wasn't done at 5500.  It was still gaining hp until the tach got near 7 grand, and that might have been 500 hp on a cold day in top tune.