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MG MGB GT V8 Factory Originals Technical - For Anyone Interested in my Rolling Road Results.

Hi All, just thought that i would post my Rolling Road results here for those who may be interested.

Spec of engine, 3.5 ltr, 9.75 pistons, Weber 500, Hurricane Cam, JWR offenhauser dual port inlet manifold, RV8 Style Manifolds, Ported Heads, Mallory Dual Point Dizzy, Mallory Promaster Coil, 14"x2" K&N air filter, I think thats about it, Now for the results.

213 BHP (flywheel)

163 BHP (wheels)

Max power at 128 mph or 5750 rpm (4th gear)

Torque 194 lbf-ft

Max Torque at 96 mph or 4310 rpm (4th gear)

Max speed 132mph (4th gear)

Max rpm 5920

Air pressure 982 mbar

Air temperature 17 deg.C

Thats about it, hope this info is of some interest to someone.
I don't know if these results are good or bad, but the guy doing the run seemed impressed.
Can anyone explain in laymans terms why torque seems to be more important than BHP, or should i start a new thread?

thanks for reading this thread, Graham.
gt young

the figures look good and are interesting to read, but do not try the estemated top speed, please, everything more than 125 MPH is beyond the limits of roadholding on an MGB.

I tried it up to 135 MPH years ago (with modyfied rollbars, brakes and suspension) and do not need this experiance a second time, although there was still more 'air in the exellerator pedal', ... you aught to be very tuff...and i failed in this task then. I felt like flying mach one with an old plane not built fot this performance...
The difference between RWHP and BHP is a little strangein the readings, i think. Normally there should not beee more than 30 BHP drop between both the mesurements, as i found out within the past.
What kind of transmission and rear axle ratio is fitted to your car?

Safety Fast!



Hi Ralph, thanks for the reply, the guy that did the test said that the drop between flywheel bhp and RW HP was about 25% in my case and that it was very good, he told me that some cars can lose as much as 50%.
As for my transmission, rover v8 vitesse gearbox, MGC back axle 3.07-1.
Thanks for the interest, Graham.
gt young


How did you engine cope with going up to 6000 rpm, it must have been glowing.

I just had mine plugged into a machine on a dyno and tested/set up. When I heard what the chap did to test it I'm glad I wasn't there!

Liam H

Hi Liam, i was very pleased with the power run, i had a rolling road test a few years ago and that was very different at the end of the run the followers were clattering alot, i thought that it had done some damage but they soon settled down.

This time no bleed down or anything (changed alot since then cam, followers etc), i already knew that it would rev to 6,000 with no problems as i sometimes let it rip on the road.

But with maximum torque at 4,300rpm i will try and resist going over 4,500 in future as there is no point exept for top end speed of course, but i will not doing anything like its top end on public roads, would be too scary a prospect anyway as Ralph as already said.

What sort of set up have you on your car? is it a factory V8 or conversion, what sort of figures did you get from your tune up (if you don't mind me asking) just interested in the differing results with different set-ups. Thanks, Graham.
gt young

It is frightening being there when the car is tested on the rolling road, thought it was going to blow up, he said that it was going to be the hottest the engine would ever get.

I was given figures of 220 fly 172 rear wheels. It did sound good though

GLG Lavis

Hi Graham from Oxfordshire, sound like good figures, what sort of set-up are you running?


gt young

My ste up is pretty much standard - 3.5, Weber 500, offenhauser dual port inelt manifold, tubular exhaust manifolds.

My instructions to the chap who did it were to set up the carb properly and check the condition of the engine, ignition etc.

All was fine, dwell angles great, electrics etc. I got a 6 page report on it all, even stuff like length of spark in each cylinder. Lots of detail.

I built it all up from scratch so the health check was more important to me at that stage and the carb set up - oddly enough it did not occur to ask about the HP!

I will next time, it's quick is all I can say.

Liam H

Hi Liam, your set-up seems simular to mine, just been looking at the photo's you posted on another thread, nice job, are you going to Silverstone next weekend?

gt young

Nope, won't be making it - I haven't built up faith in the car yet! plus two wee ones make it hard - I am going to try to get out and abut next year, and meet some of the names on the BBS maybe?

Liam H

"Can anyone explain in laymans terms why torque seems to be more important than BHP"

I'm as about a layman as you can get, but here's my take on the subject:

The opening sentence in the original article, as I published it, was "Horse power IS what Torque DOES!" For some reason, Curtis cut that from the article when he put it on the internet. He also cut the equation I gave, HP = (torque X RPM)/5252, and the diagram I had explaining the deriviation of this equation.
Dan Masters

Looks like the numbers are in the ball park to what I found out with my car a while back.

Stock '80 SD1 3.5 + LT77 5-speed, Edelbrock (Weber) 500 cfm carb, Edelbrock Performer Intake, MGC 3.07 gears, RV8 headers, pertronix ignition, K&N 14" filter with "Extreme" top. Carb rejetted 2 stages lean from out-of-the-box configuration.

HP @ 4740 rpm: 143 @ wheels
Torque @ 2500 rpm: 188

I've since installed an MSD ignitor box to help clean up emissions and get it to run smoother but haven't taken it back for another run yet. Will be interested to see if it makes a difference.
Simon Austin

I always thought that :

Torque : effort in, measure of energy input.
Horsepower : energy out, measure of work done.

I think that is the same as Dan's article says?


Liam H

WOW! Dan, thanks for that, i have read your article a couple of times and i think it's sinking in (it's still early)if you consider yourself a "layman" i don't hold out much hope for the rest of us (well me anyway). Thanks again.

Simon, thankyou for your reply that was the sort of information i was looking for, as i have no idea if the set-up that i have is "delivering what it should" (although the guy doing the tune said he "was impressed") you are never really sure until you see figures from other simular set-ups. Thanks again.

Liam sorry you won't be able to attend Silverstone next weekend, maybe next year.
I am glad that you understand the difference between Torque vs Horsepower, but i note that you say; "i think that is the same as Dans article says". I will have to read it a few more times, but i am a bit thick, and it is still early. Thanks again.

Graham young


I'm in Blackpool,which rolling road did you use, I'm after maximising mid range torque, ad need a rolling road locally.

'Horsepower sells cars, but torque wins races' C Shelby.

Just finished watching Le Mans...the Audis are alleged to have nearly 1500nm of torque, I reckon that's nearly 10 times what our V8's are putting out !
M Barnfather

Just washed car ready for Silverstone took it for a steady run round to dry off any moisture before i put it back in the garage.

I noticed that it was running about 10 deg hotter than usual, checked it out when i got back home and found that the heater valve is leaking, that power run will certainly find any weak spots, still if that is all that it showed up i am happy, and still plenty of time to get a new one and fit it before the trip to Silverstone.

Just thought i would share that with you all, thanks, Graham.
Graham young

I know, I know, Mr. Masters.
The difference between hp and torque is:
hp #'s is for bar stool/pub racing
Torque is what you really need, or what really counts.

If you are a laymam, then, I do not know what I am.

Bill Guzman

Hi Mike, i used Mini Sport in Padiham (near Burnley) the guy is well respected, and has a very good reputation, no bullsh*t with him if there is something not right he will tell you, and will not try to mask the problem.

He is self employed at Mini Sport and only tunes cars three day's a week Thursday, Friday, Saturday, the rest of the time he runs his other buisiness building Ford racing engines (which ones i don't know)Mini Sport don't let anyone else tune cars so when he is not there they don't do any, even when he is on holiday.

If you are interested the cost for a modified v8 is 100.00 including vat, he allows 2 hours, but if, as with mine he couldn't improve over how it was he won't charge you the full ammount, he only charged me the cost for a standard 4 clyinder 60.00 inclusive, so can't grumble, also he is more than happy for you to stay with the car and pick his brains. All in all a good guy.

Telephone 01282-778731

Thanks, Graham.
Graham young


That sounds very reasonable....and not too far away....I wonder if he is any good at re-chipping ECU's (mines an EFi, and needs a re-chip for the mods I've done).

I think a call is in order !
M Barnfather


Horsepowers sell cars... right.
Torque winns races... also right.

If you only go for top speed you need horsepower, the more the better (although you will reach the limits of the poor MGB very soon).
If you go for top speed in a 'flash of time' you need torque and the right gearing. Horespower will be a gift too.
Just think upon top speed of the B, i got problems at 135 MpH, a friend tried it on a race curcit and got problems at 142 MpH, another driver around here was proudly reporting of his perfect car, capable of 130 MpH with the ST front spoiler.
Very nice readings but what are they good for?

If the V8's suspension is modified to coope with the power and you like to have a competetitive car that still looks like a B or a B GT, don't be fooled by the figures. More than 130 MPH with a roadgoing B V8 will be lethal sooner or later!
If you like spoilers or headlight cowls for street use, just go for another (more modern) car.
Just calculate your transmission and rear end and you will find out what Caroll Shelby had on his mind in the erly 1960's and who of us needs a MGB V8 that can be driven at more than 120 MpH with joy?


I tried differnt rolling roads without any changes to my car's engine configuration. Readings were from 221 to 173 RWHP. I am not sure whether the operators knew about the programming of their rolling road or whether the programmers did know enough about the engines. And when HP at the fly is quoted, is it a calculated SAE reading, a BHP or DIN reading, the Italian way of mesurement or on what basics or scalation are these results monitored?
(SAE explanes the drop of HP through the drive train, it does ot even include engine auxillaries that are needed to run an engine, pumps, generators, distributers, ventilators... !)


I'm with you all the way Ralph.

The thing I love about the V8 is it's ability to pull hard at low revs, some years ago my brother had a Celica , quite a good modern coupe at the time, but typically Japanese...all revs and no torque, when we drove in convoy he used to complain that I shot off like a rocket from motorway services, and it took him miles to catch up....but I seldom go above 4000rpm in the V8, and just didn't realise how slow off the mark other cars are.

Interesting point about rolling road readings....I'm not the slightest bit interested in some theoretical calculation of power loss, just wheel torque, thank you !

I've heard before that readings can vary depending on the skill of the operator, best use the same road each time, and for comparison purposes only.
M Barnfather


He definatly is into re-chipping, just give them a call tell them what you have got, and what you would like to achieve, or you could call in on a Thur, Fri,or Saturday, watch him at work and talk to him direct before making your mind up, like i say he is very open and passionate about what he does, and loves a challenge.(and NO i am not on commision ha,ha).

On the topic of rolling roads he say's that some rolling roads are way too "generous" and with his "what you see is what you get".


I have no intention of going anywhere near the top speed potential even of my car, the 132mph in 4th that i qouted on my thread was a reading from the rolling road, no wind resistance etc, i doubt it would reach that on the road (but i will never find out even at Silverstone this weekend) i have had it upto 125mph and i did not like the feeling of lightness in the steering that was enough for me, its the accelleration up to a given speed that i enjoy the most.

Graham young


that is exactly what i ment. The bonus is the power on demand due to the torque of this fantastic V8. Practical and theoretical top speed are just figures and do nothing for the fun we have with this nice little cars.
What do they say on the other side of the pond... nothing beats cui but cui. Who cares upon top speed? Who is on the run? Just enjoy the fun and what did they say during the last years of MG-Rover "Life's too short", not a faulty diagnosis in my opinion, when the V8 is waiting for you!

It is not the top speed that makes the V8 that enjoyable, i learned, it's the torque that makes it always a fun to drive and the outstanding performance of the V8 that still takes you to performance readings at normal motorways driving conditions, where upon many modern cars (and their makers and drivers) of this size only can 'dream upon'.
It is not the top speed that counts as i learned, it is simply the kind of agility that i did nof find anywhere else on a comparable normal car of this size (and price range), not even in my Alpine 310A up to now. May be there are some i never noticed, but do they have that 'honest character' or personality that an MG can offer? Are they able to become a member of the family or are they just companions for a couple of years?

The B V8 is simply a perfect cruiser, although historical by now, still one of the best interpretations of a Grand Touring Sportscar, the kind of car Paddy Hopkirk always asked for during his days at the Special Tuning Department at Abingdon.

With the V8 noone must ask for horsepowers, i think. When it is maintained well, it is one of the best classical cars money can buy.

I am in love with my GT V8 since spring 1979 and can't get enough of it.



Good luck at Silverstone...I did the last 'parade laps' there, and was put at the front of my lot with a video camera, I'll lend you the DVD if you like...I'ts hardly Spielberg, but I fixed the mike in the over-rider above the lots of sound, and vicious acceleration.

I only managed 100 on the main straight, but was conscious of the words of wisdom from my better half 'It's nearly 200 miles drive to get back home'

Email me at mgbv8mike(AT)spamcop(DOT)net with your address and I'll lend you a copy.
M Barnfather

Well, I don't have any offical figures, but I got out for the first time on the A19 last night, waited until I was doing 35 in 3rd and then floored it.

24 hours later my eyes have only just returned to their sockets. You can still see the imprint of my ribs in the driver's seat.

Liam H

This thread was discussed between 15/06/2007 and 27/06/2007

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