View Full Version : BHP- Fact or Fiction?

03-02-01, 09:10 PM
I am in the process of building a DAX Tojeiro and will be considering ordering my Engine shortly. I have the chassis jigged up to fit a Chevy small block,Tremec 5 spd, through to Jag 3.31 powerlock final drive.
I am amazed at the different BHP and TORQUE figures some of you guys state that you think?? you have.., QUESTION FOR THOUGHT though..HOW MANY of you HAVE had your Cobra Dyno`d and can sleep at night with the comfort knowing that YOUR vehicle is punching out the BHP and TORQUE that you was lead to believe when you purchased your engine.!
Love to hear from you, - wonder what the best and worse scenarios would be? Are these figures we are lead to believe, when we spend our hard earned cash-
FACT or just FICTION???.... Get your Answers in now.

04-02-01, 11:46 AM
I was in Atlanta, Georga, USA in September last and I went shopping for a Camshaft for my Chevy 350. I put this question to the guy and his reply was that when Chevy were making 350's in the late 60's and early 70's, they were reconed to produce 1 horsepower per C.I. It was really just a rule of thumb. So using this rule, every 350 C.I produced 350 H.P. Then the rules changed. Some legislation came into effect which standardized the horsepower into what we know today. Therefor some of the die-hards and also older literature regarding these engines maintain that the figure of 350 H.P ie 1 H.P per C.I is still relavant today. As it turned out when the standard was changed there was a huge outcry because somebodies beautiful, powerful shiny Chevy, and Ford V8's had lost, on paper, about half its power. As you can imagine, ther were alot of @?&&*$ off people around.
That is the explanation given to me. If anyone knows different, it would be interesting to know other theories.


04-02-01, 11:50 AM
Well, A bit of faction and fict ;-)

When I bought my engine from a bloke in Nottingham at All American Autos, he told me he was building a 350HP chevy with new this, new that etc. I should have know when the engine turned up that he was rubbish as the engine has a broken water jacket, not very good for a new engine.

After a lot of hassle, he replaced the engine, or rather just dropped it off at GD for me to get it installed. The second engine was only firing on 7, and the pressure on each bank was very low. After some investigation, we found out that the pushrods were bent, and had been used before. Anyway I digress, just think twice before you buy from All American Autos.

On to the BHP figures. This chap at All American told me the engine would produce around 350BHP. I was very sceptical after the problems I have had with the engine, so I took it to a local rolling road in Northampton.

The engine was putting out 180BHP, nowhere near the 350 he told me it would. We finally managed to get the engine up to about 250BHP after a lot of messing around etc.

Over this winter I have had the engine re-built by Ken Coleman of Engine Data. We have used turbo pistons, etc etc. The engine has been blueprinted and balanced and normally aspirated porduces 350BHP. With the blower at 12psi, we produce around 520-530 BHP, and then add the intercooler on and it adds about another 50BHP.

These figures are purely vapourware at the moment as the engine has not been dyno'ed. The engine will be dyno'ed at the end of the month and I will let you know what the actual figures are.

I reckon the figures will be spot on as Ken has been doing this for a long time and has the experience to know what an engine will do based on the components he has selected.

Best Regards


04-02-01, 07:41 PM
When I ordered my engine from Real steel I took the option of them running it up on their dyno it cost an extra £200 (fuel.fresh oil&filter.etc,)but I now have a print out showing me exactly what I got for my pennies.(BHP.Torque.Carb air flow.Oil pressure.etc,)
Having said that I know it's not telling me what's at the wheels but then what the heck I'm happy

06-02-01, 11:27 AM

When you say your engine initially put out 180bhp was this at the wheels ? If not what did it put out at the wheels ? It seems to me that you loose a hell of a lot of horsepower through a Tremec/T5 & Jag rear end. I have chatted to guys from the Australian Cobra Club and some of them have had engines dyno'd at over 400bhp at the flywheel(one example was a Ford 351 Windsor with an Edlebrock rpm package). When installed in the car they where getting about 280bhp(208kw) at the wheels through a manual box and Jag rear end. My Dax has a mildy modded Ford 351 Cleveland/Tremec which put out 230bhp(170kw) at the wheels. Even though the carb needs jetted properly. I figure this is over 300bhp at the flywheel. All this talk about flywheel horsepower is bollocks anyway it's what goes to the road that matters. I think a better mesurement is performance. I have timed my car 0-100 in about 11 secs. Can't complain at that. There was an article in Car & Car conversions recently about a Dyno Day with a Lotus seven club. This rolling road was able to measure rolling resistance by slipping into neutral at high revs and measure resistance as the revs dropped. This way they could predict flywheel horsepower from wheel measured horsepower. There was a Ginetta(I know its not a seven) with a Rover V8 that put out 210bhp at the wheels but predicted flywheel power was over 280bhp. Don't know what kind of box/rear end this has but I reckon it's probably not as heavy duty/power consuming as a typical Cobra transmission.

06-02-01, 05:13 PM
Bhp figures are a waste of time in my opinion.
If u look at some figures in some books/mags etc.
What u find is a load of boll$%^* most of the time.
e.g. a cossie engine in full tune at say 400bhp is only a fraction quicker than one at 300bhp if u look at the (here comes the magic word)TORQUE!!!!
Figures theres not a deal of difference.

In my opinion the winning combination is high torque-correct gearing-
the weight of the car and last how u get the power onto the road!!

BHP is just a bi-product of rev-ability and torque.

If u dont agree the look at it this way:-

Put a 160 bhp fireblade engine which revs high into a 5-tonne truck
Then try a 165bhp Rover v8 in and lets see which one will actally move!!!!

Ya see bhp what a load of crap.

Its those three little letters that get the unwise to reach for their wallets though

06-02-01, 05:38 PM

Couldnt agree with you more, its the torque which equates to acceleration and top speed.

Mind you, my supercharged engine puts out about 500lb foot torque.

I once read an article which detailed in laymans terms what the difference between horses and torque was, I will try an dig it out.

Best Regards


07-02-01, 10:09 AM
I agree with the comments about torque. However surely the max torque isn't the only important consideration. The torque curve is important which is reflected in the BHP figure. If you compare like for like an engine with a broader torque curve will give better performance throughout the rev range and hence have a higher BHP rating.

08-02-01, 08:22 PM
Agreed but the torque has too be there.Fact!
In my eyes the ideal engine would be one to give good flow
right through.
I don't like 16 valves much cause i like to feel a bit of "punch"
(caused when then engines flow/timing/cam r just right)
But they rev higher which gives a broader "canvas" to paint your
curves on.
My rover engine is only really good for upto around 5500 for street
use but i have put the (i hope)right parts on to work from 1500-5000
so it should all come in together
So really if someone could put together a light revy 16v v8(say chevvy)
My guess that it would be a good engine in standard form.

The other way of thinking is weight.
Stick a revy engine in a v.light weight car and u have your speed back

So do u go for swing or roundabout?

For longevity give me torque any day!(i've never seen a 12000rpm bike engine do
200,000 miles!!!)

09-02-01, 04:38 PM

All the figures quoted were at the wheels.

Regarding loss through the transmission, at the start of the session we were seeing losses of about 45bhp through the transmission, and when the dif oil etc warmed up it got down to about 30bhp loss through the transmission.

Best Regards


13-02-01, 06:11 PM
Interesting subject - claimed power figures. When I had my new engine built (a small block Chevy 400c.i. + 0.30"), I insisted it was properly dyno'ed. O.K. so it is not cheap (approx. £450 per day + fuel/oil/parts) but given the overall cost of engines generally, I considered it the most important bit. Also, do remember there are 3 sides to engine dynoing:
1. The engine gets "run in" throughly and properly
2. The carb. can be jetted & set up, as well as the ignition curve/distributor
3. You get accurate power figures; not Mickey Mouse guesses.

In my case, that resulted in a genuine 451 bhp & 516 lbft torque. You may be interested to know, this propelled my AK 427 to 173mph at Le Mans last year with a bit more to come !!!
Best wishes
Simon Winfield

15-02-01, 04:19 PM
If only it was as simple as how much bhp or torque the engine produces.
The engine is one of many factors. Weight is a huge consideration, gear ratios, dif ratios, traction on the line, internal friction are all features that go into taking a Porsche at the lights.

Horsepower and torque are important in different situations. Earlier on someone mentioned a V8 moving a lorry, great if you want to move a lorry! but I am happy with bhp moving my ultra light Cobra, and when I want to pull trees over I’ll use a Landrover.


16-02-01, 03:22 PM

Someone didn't read the whole post!!

Ya know the blade engine bit...

Like er.. light weight bit...

Anyway if i have enough torque to beat a porche AND pull a tree down
I wouldn't need to buy any other car!!

With out ragging anyone else up let me give u another good example

Lotus Elise...

Fine off the mark "but what i hear u say no top end!"

Not enough torque in the engine dept.!!!!!!!!!!!

If u geared that car to do 160mph it would do 0-60 in 13 secs!!!!

Then it would never get to 160 like most (ordinary) cars in top
gear it would'nt rev past 4000rpm..

I wonder why?

My last example.

take an engine that will rev to 30,000 rpm but only has 20ftlbs of
torque it would never even start cause it wouldn't have enough torque
to spin its own crank!!!!

Then take an engine that has 100ftlbs of torque but will only rev
to 1000 rpm (thats 60mph in a chevvy powerd cob) ticking over in top gear!!!!!!!!!!!!!!!!!!!!!!!!!

Now does that put this to bed?



16-02-01, 07:12 PM
For those anoraks who don't know and wish to. Hopefully this message will self destruct in 2 days. Please.

Torque is defined as:

Force x Moment Arm = Torque
In the English system, torque is measured in "foot-pounds", "inch-pounds", or even "ounce-inches".

In the Metric system, torque is measured in "Newton-meters".

8.851 inch-pounds = 1 Newton-meter
1 foot-pound = 12 inch-pounds
16 ounce-inches = 1 inch-pound
1 Newton = 1 kilogram-meter per second squared
A 1 horsepower (746.0 watt) motor operating at base speed of approximately 1750rpm produces 3 foot-pounds of torque. The formula is as follows:

(horsepower x 5250)/rpm = foot-pounds

(Foot-pounds x rpm)/5250 = Horsepower

16-02-01, 10:16 PM
LAST EDITED ON 16-Feb-01 AT 11:21 PM (GMT)[p]LAST EDITED ON 16-Feb-01 AT 11:17 PM (GMT)

Someown told me about a shovel analogy, however the names have been removed to protect the innocent and I can neither confirm nor deny the previous or subsequent comments and have no prior knowledge or the fact or anything. Thats the disclaimer bit done then!!

Torque is the shovel, BHP is the number of times you have to use the shovel to move a given amount of horse muck.

The bigger the shovel the lower the BHP needed to atain the required result, the smaller the shovel, etc etc.

Technical Equation as follows.

Shovel * Width * Length / quantity and consistency of horse muck=BHP, however as the consistency of Horse Muck is not a constant (I speak from experience unfortunately) the equation will loop and loop and loop and loop........................
Best Regards


18-02-01, 11:59 AM
Torque, the best example I know.

A man wakes up with a hard on a needs to go for a pee, so off he trundles to the loo. As he pushes said member down to the required angle of attack his feet slip back from under him. Thats torque.

18-02-01, 01:26 PM
No its not its boasting!

Your last reference to "Torque" should have been "Talk"

18-02-01, 02:47 PM

06-03-01, 09:24 PM
Well....This certainly seems to have put the cat amongst the pigeons so to say! I am still trying to decide whether to import a crated ZZ4 or to purchase one from Repower or Reel Steel. Have you guys had any dealings with these ? Cheers Peter

17-03-01, 09:35 PM
how do you know if it will do 30,000 rpm at 20lbs ft torque if it won't start

20-03-01, 06:19 PM
I bought a brannie 351w with complete edelbrock performer rpm kit and tremec 5 speeder from brian at repower.

The claimed is 400bhp and 418ftlb - whilst not yet dynoed (waiting for 2000 miles run in) - My SRv8 (jag based) goes like stink, takes porsches at lights and can probably pull up trees too.

I to will be interesed in seeing the actuals - will they match the bhp and torque curves shown on the edelbrock website????

Will advise 0-100 times later - its certainly big grin territory however long it takes.

As for Repower and Bryan - good service - I can't fault them (Bryan - you owe me a drink).

p.s. 5th gear on the Tremec is very tall and makes good use of the V8 (any V8) torque for cruising - 100mph at 2,700.

22-03-01, 07:13 PM
I have used Real Steel, and know others who have done so as well. They are honest and very knowlegable, all the Hot Rod brigade use them. Don't expect cutomer sevice al la Marks & Spencer, but they are enthusiastic and helpful.
You will also do well to beat them on price outside of the States as well.


24-03-01, 01:38 PM
>I bought a brannie 351w with complete edelbrock performer rpm kit and
>tremec 5 speeder from brian at repower.
>The claimed is 400bhp and 418ftlb - whilst not yet dynoed (waiting for
>2000 miles run in) - My SRv8 (jag based) goes like stink, takes
>porsches at lights and can probably pull up trees too.
>I to will be interesed in seeing the actuals - will they match the bhp
>and torque curves shown on the edelbrock website????
>Will advise 0-100 times later - its certainly big grin territory
>however long it takes.
>As for Repower and Bryan - good service - I can't fault them (Bryan -
>you owe me a drink).
>p.s. 5th gear on the Tremec is very tall and makes good use of the V8
>(any V8) torque for cruising - 100mph at 2,700.

I would also be interested in the actual dyno figures when you have them. Do be aware that U.S. dyno figures are always higher than U.K. figures because an english dyno will be a 'true' nett figure. The Yanks do strange things when calculating water pump drag, mechanical fuel pump drag, etc.
'Ultima Sportscars' openly admit that the engine in one of their press cars is rated by the Yank's at 534 bhp, but is in reality closer to 450 bhp.
You say you'll get it dynoed when you have run it in. One of the main purposes of putting an engine on a dyno is to allow it to be run in properly under safe, measured conditions in the first place. #
Let us know the results whenever. Good luck.

02-04-01, 08:16 PM
Update coming up from your favourite Cobra Bloke (artistic license, and if anyone disagrees, I shall delete them from the user database)

The engine is built, and naturally aspirated runs at around 360hp, don't know the torque so we won't have to start on that one again, on 8:1 compression. It arrived with Ken as a quivering mess and looked rubbish, it now looks like a proper engine with Edelbrook performer RPM heads, Victor jnr manifold, turbo low compression pistons, the works!!!!

The supercharge is being mounted shortly and the Dyno is booked for the 11th and 12th, so I shall let you all know how we get on.

Its being run on the Wednesday to bed in etc normally apirated and ensure everything is OK, and we willl be putting the Charger on Thursday, without the intercooler first, then with the intercooler to find out what difference it makes.

We are also testing the GD heads as they are only rated to something like 500-550 BHP, so we shall see if the restrict the flow and I might have to go from a 2 1/5 inch system to a 3 inch system, who knows..

There has been a lot of interest in this application, and a full article will go up on the site and in Snaketorque.

All the best

Cobra Club Web Bloke with a Supercharged GD!

PS Short Stroke engines are all front and no grunt, everyone knows a long stoke is much better!!!!! (stir stir stir) }>

02-04-01, 09:15 PM

This equation seems a bit off to me, maybe I am not seeing it right but...

(horsepower x 5250)/rpm = foot-pounds

(550hp x 5250=2887500)

2887500/4000rpm=721.875 lb/ft torque, and with the best will in the world, I don't think that this is right, if it is then I have built myself not just a fun car to drive, but an undrivable car thats not fun. If its right then errm, buy shares in the Brown Trouser Company.


Cobra Club Web Bloke with a Supercharged GD!

03-04-01, 08:02 AM
yeah but he who has a longer stroke will not last so long! he he he he he !


(ps best of luck).

04-04-01, 06:34 PM
This may help, but then it may not. Have a ponder.

1 HORSEPOWER(HP)=33000ft lbs/min
=550ft lbs/sec
You may be able to do something with this.

22-04-01, 09:52 PM
Well that certainly provoked alot of response. After alot of deliberation i have decided to sod the expence, after all you might as well do it once and do it properly. I have ordered a 420bhp / 418 lb torque 5.7 ltr Chevy 350 from Repower. This will be fitted with Edelbrock Performer RPM aloy heads with swirl polished valves.
Edelbrock Performer camshaft and timing set
Edelbrock Performer high rise dual plane RPM intake manifold
Aluminium roller rockers, hardened push rods
Keith Black pistons, high volume oil pump
Block will have oil passages enlarged and deburred
plus loads of dressed up goodies

I will also be uprating the package to a billet flywheel and heavy duty clutch
to match up to the Tremec 3550 gearbox

I am also thinking of uprating to a MSD billet distributor andhigh output coil etc., and Possibly the Edelbrock aluminium water pump
Its all knowing where to draw the line.
This little lot is going to cost me about £7.5 K, but after shopping around and even thinking of importing the unit Repower seem as competitive as any
Would be interested if any of you guys have used the MSD distributor and or waterpump for any comments
Here`s counting down the days Peter

23-04-01, 09:07 PM
You built the bloody thing. No, seriously I agree that doesn't seem to work. I must admit I couldn't tell you why not.