How much horsepower does a 727 take to operate..........

[cdr]

tires on a chassis dyno can make a big difference , on my Motorcycle dyno a street tire designed for a cruiser, low speed tire, would dyno 5 hp less & 5 lb torque less than a high speed tire, so at 100 hp, 5 hp loss is a lot on a 500 lb motorcycle.  

[68pplcharger]

tires on a chassis dyno can make a big difference , on my Motorcycle dyno a street tire designed for a cruiser, low speed tire, would dyno 5 hp less & 5 lb torque less than a high speed tire, so at 100 hp, 5 hp loss is a lot on a 500 lb motorcycle.  

That is true because you can add or subtract rotating mass depending on the wheel/tire combo

[Kern Dog]

I wonder how difficult it would be to rig up a test for spinning a trans, drive shaft, axle and rear tires. ALL of this driven by some electric motor with the only goal to be the determination of the power required to get it all up to speed. THIS would highlight the exact amount of power loss any engine sees.

It would eliminate many variables. It seems that most transmissions would have similar numbers, same goes for drive shafts and axles. The one variable might be tire and wheel, since smaller and lighter tires/wheels would require less HP to spin.

[1974dodgecharger]

tires on a chassis dyno can make a big difference , on my Motorcycle dyno a street tire designed for a cruiser, low speed tire, would dyno 5 hp less & 5 lb torque less than a high speed tire, so at 100 hp, 5 hp loss is a lot on a 500 lb motorcycle.  

U r correct cdr.....the dyno operator. On my car always tell me if u want bigger numbers I would n3ed to ditch ky 20s in the rear......he said I probably have. 20hp loss....no big deal to me im not chasing the numbers purely. ..

[metcoll]

my 440 bored 30 over with six pack pistons, lunati 240/250 @50 520/547 cam 452 heads that were rebuilt mild porting standard valve rpm intake 750 dbl pump holley through headers which would should dyno 440-450 on engine dyno...we put it on a dynojet and dynode 330 @ the wheels...this is through a 727  with 4200 stall & 4.56 gears..

[Kern Dog]

My 440/493 with Edelbrock heads, 2" headers and a 292/509 cam was close to the 500/500 engine that the MOPAR dealers were selling at one time. MIne should have made 500 HP at the crank but only registered 369 at the wheel through a 727, an 8.85 with 4.10 gears and a 28" tire.

[BSB67]

tires on a chassis dyno can make a big difference , on my Motorcycle dyno a street tire designed for a cruiser, low speed tire, would dyno 5 hp less & 5 lb torque less than a high speed tire, so at 100 hp, 5 hp loss is a lot on a 500 lb motorcycle.  

U r correct cdr.....the dyno operator. On my car always tell me if u want bigger numbers I would n3ed to ditch ky 20s in the rear......he said I probably have. 20hp loss....no big deal to me im not chasing the numbers purely. ..

No estimate on my RWHP from my earlier  question?

[cdr]

oops #2   

[1974dodgecharger]

I still say 30 to 35 percent loss with 727 tranny.

How much loss with a manual transmission?

I rebuilt my tranny, whole rear end, and I'm an amateur on the lowest scale.  My 383 day ode on engine stand at 500hp. My power to rear wheel is 383hp with my manual.  I say 25 percent and yeah I'm sure a better build can do 20 percent loss.  I saw guys claim 600hp with their 727s and only put down 300hp at bests and there is a YouTube video with a blown 440 with nearly 700hp put down 450hp to wheel......and I like to go to Dyno sessions a lot and saw roughly same results over and over with our classic  molars that's why I think a lot of folksy ONG like Dyno especially old classics results r always disappointed.  


I'm doing another Dyno session in 2 weeks to tune my methanol and nitrous together to see what I get and how much is gained each one and test my cut outs.

How much additional hp loss for the driveshaft, rear end, and axles and tires?

The car in my sig, what do you think the rear wheel hp is?  

Here is more info, if that helps:

http://508charger.yolasite.com/

hard to say I like to estimate it as a whole with 727 and whole rear end etc...with a run of yours at 11.67 e.t.  with those 3.23 gears im sure you have more than 500HP....engine wise.

[440]

I'll take a Stab at BSB67's car and say about 430 - 450 RWHP?

[BSB67]

I still say 30 to 35 percent loss with 727 tranny.

How much loss with a manual transmission?

I rebuilt my tranny, whole rear end, and I'm an amateur on the lowest scale.  My 383 day ode on engine stand at 500hp. My power to rear wheel is 383hp with my manual.  I say 25 percent and yeah I'm sure a better build can do 20 percent loss.  I saw guys claim 600hp with their 727s and only put down 300hp at bests and there is a YouTube video with a blown 440 with nearly 700hp put down 450hp to wheel......and I like to go to Dyno sessions a lot and saw roughly same results over and over with our classic  molars that's why I think a lot of folksy ONG like Dyno especially old classics results r always disappointed.  


I'm doing another Dyno session in 2 weeks to tune my methanol and nitrous together to see what I get and how much is gained each one and test my cut outs.

How much additional hp loss for the driveshaft, rear end, and axles and tires?

The car in my sig, what do you think the rear wheel hp is?  

Here is more info, if that helps:

http://508charger.yolasite.com/

hard to say I like to estimate it as a whole with 727 and whole rear end etc...with a run of yours at 11.67 e.t.  with those 3.23 gears im sure you have more than 500HP....engine wise.

So I've gone back and re-read your posts (and many of the others) to see why you think 30 to 35%.  I really don't have any science or theory to add to this thread that has not been already been kicked around.  

Your last response is what made me go back to look at your other posts, as your last post shows that you are not that much of a student on this subject. Please don't take offense, as I think you have indeed made some good observations, but have come to the wrong conclusion.  It sounds like most of your info/observations come from observing chassis dyno results, probably at events?  Is this correct? If it is correct, my conclusion would be different than yours.  Instead of a 30 to 35% power loss, I suspect that people (owners) are wrong in what they believe is the actual engine hp output to begin with.  There are several possible reasons for this: 1) They are guessing at engine hp (magazines, buddy's stuff, someone told them, they figured....) 2) the engine dyno results were somewhere between happy, and very happy (pretty common),  3) there are other non-drivetrain parasitic losses going from the engine dyno to the car (water pumps, fans, power steering, 4) The exhaust systems are usually different, possibly way different between the engine dyno and chassis dyno, and finally, 5) the in-car engine tune-up is not right.   These can add up to large hp discrepancies that some explain away as drive train losses (way better than saying that my "500" hp motor actually makes 450 hp).   And all of this is assuming that both dynos are being corrected to the same standard conditions.

Before chassis dynos got so popular, people would actually run their cars at the track.  Because the car normally performed below expectations, just like on chassis dynos today, the excuse was "poor traction" (verses drive train loss).  Of course, mph is independent of et, and no matter how poor the traction, you can get fairly accurate hp info from the track mph.  Back then with track data, as today with chassis dyno data, people find excuses to explain the results, verses accepting the reality that their engine simply does not make the power they thought.

So here is my observation.  When I have good engine information, good engine dyno information, good engine chassis dyno information, and actual track data w/ atmospheric data, they usually align and show the hp loss due to the drive train is 17% to 23% on auto cars.  I'm sure there are cars outside this range, but I would say that these would be the exception.

[Volaredon]

1st post here. been wondering the same thing, found this forum via  a Google search to see how much power loss thru a 727 vs 904.
I  recognize some of you guys from FABO, the /6 forum, Moparts, etc at which I have posted for years.
My truck; 85 D150, "SLANT 6" (yeah I know) but it has a 727. 3.2 geared 8-1/4
I'm asking because I am tired of guys saying to "ditch that 727 and put a  904 in there".   a 727 oughtta be all but "unkillable" behind a slant. So I want to leave it there. it IS a truck, it will be mostly daily driver but sometimes pull a light popup camper or utility trailer with a garden tractor and a push mower or 2, ~30 miles at a  time..... (though my camp trips are 10x that far from home) I have a replacement slant in the machine shop as we speak waiting for teh "Tim Taylor... more power" treatment. Keeping the /6 "just because" most people wouldn't.  Unsure at the moment the extent I will build it up.... thinking of adding a draw thru home brew, junkyard parts sourced turbo setup.... that idea is still out for debate.  I have burnt up more 904s in daily driver use than I care to remember in plain ol' daily drivers, I have always had better service from 727s in general....
but if (as some say) it takes 100 hp to run a 727 then how does this thing accelerate (at all) and even pull itself at much more than a crawl? The stock slant only has about 100hp to begin with.  my new one will be hopefully about double that.
I have also heard various percentages of engine power, is the answer? so lets pick a number. 25% seems a commonly heard figure. So then a 727 robs 25 hp from my slant, where  it would consume 100 hp from a 400 hp big block? (assume for just a minute, that I could yank the slant and drop in a big block and bolt it up to this same trans, though we all know it can't happen) so chassis, tires, gear, trans and converter would all be the same  between the /6 and a BB. That does not seem logical either.  Each drum, planetary weighs the same no matter which engine is in there. It takes the same amount of HP and torque to overcome band friction and get things moving from a standstill. Right?  In this scenario, same TC so same amount of fluid being displaced and such so that should stay constant, right?  Aerodynamics the same, as we're still talking the same 85 D150 no matter which engine is in there.

I plan to retain the 727 and the 3.2 gears. Unfortunately I know of no A518 or 46RH that was cast with a slant 6 bellhousing. so "if" there were to be a trans swap down the road, it would be to something with an OD gear.... meaning probably a manual of some sort.  Otherwise the 727 stays.


Since this is my 1st post here, a little about me.  53 yo, from Kankakee IL, I work as a fleet mechanic for the miserable state of Illinois.
I had a Charger as my 1st car.. a '76 Charger SE (basically a Cordoba)   I tried in vain to buy my brother's '68 when he went to sell it... my favorite Charger is a toss up between that '68 and the '73-74s.  and have never owned anything besides a Mopar.  Hope I don't have to either.  Newest vehicle owned to date... (still have, its the wife's daily) an 01 Durango with a  360. Have never, and hope to never own a FWD anything.

[XH29N0G]

Volaredon, 

First off, someone else will know about the 727 vs 904.  I don't.  But there was one thing about your post that struck me and that was the 100hp loss (compared to a loss that is proportional to rotations).  My assumption is that (1) the loss for any given (constant) rotation rate (speed) should be the same regardless of engine, but the loss will (2) vary with rotational speed (3) might be different for different gears, and (4) vary a little bit with the rate at which the rotational speed increases during acceleration. 

Point 1 would mean you would be pretty near 0 HP loss at low RPM and is why you can move and point 3 is what lets you drive in 3rd gear without losing as much power. 

[BSB67]

As rpm and load go up, the power consumed by the transmission will go up too.  Is it linear?, I don't know.

Going from an engine dyno to a Mustang chassis dyno, mine lost 21%.

[cdr]

As rpm and load go up, the power consumed by the transmission will go up too.  Is it linear?, I don't know.

Going from an engine dyno to a Mustang chassis dyno, mine lost 21%.

Hey Russ, what all was on the engine for the Flywheel dyno, ? stock ex manifold, water pump, fan ,, ECT

[BSB67]

Good question. No fan, no alternator, minus full exhaust.

[c00nhunterjoe]

While i cannot give you a hp number, i can tell you that going from a traditional heavy duty 727 to a protrans, it is worth 2 tenths in the quarter mile on a 10 seconds car.