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MG MGB Technical - How Much Grunt From Your B?

Hi,

My B has been rolling roaded at Dynoplot and is pushing out 115bhp. they tell me that this is impressive for a B. What bhp are other modified B engines pushing out? as i would like to compare and see if and where other people may be getting more power from.

Cheers Joe
joseph phillips

Joe
What's your specification on your engine?
I have done a stage 2 head, 715 cam and 1860 rebore, so hope to be getting reasonable outputs when I get it set up on a rolling road. That will also include an upgrade to K&N airfilters and lumention upgrade. Which r/r did you use?
Martin

Martin,

Mine is a standard capacity with:
Stage 3 head. Gas flowed, ported, polished with larger inlet and exhaust valves.
Skimmed head and block 11.5:1 compression
Triple branch mild steel manifold, stainless steel back box
45 Weber, ITG air filter and Pipercross cold air feed.
Piper 285 cam
pipercross oil filter(instant oil pressure at start up. At last found one that works)

It produces 115.1BHP at 5531RPM

The R/R used was Dynoplot and they said that it was the most powerful B they had tested.

Oselli said that I should expect around 125BHP if i go up to 1950cc at the cost of 1200pounds!! Think that can wait.

Martin,

Who did the work on your cylinder head?
joseph phillips

Has anyone had their crankshaft hardened? If so how much does it cost and what are the benefits?
joseph phillips

Joseph, was that bhp figure at the wheels or at the engine?
Chris Betson

I'm going to get RRed in the next couple of days just for the hell of it. I'll let you know the results so you have something for comparison :o)

Anyone used Stealth Racing? http://www.stealthracing.co.uk/
They're just down the road from me.

Cheers,
--
Olly
Oliver Stephenson

I had my crankshaft hardened. I don't remember the cost but it wasn't much. THe advantage is a slightly smoother engine. I'm not sure if it's noticable or not really since I did it during an engine rebuild.
Steve Simmons

I had my stock engine on the dyno after putting on some K&N filters. 66 horses at the wheels. Look out, here I come!
Dana Wilson

Chris,

The power is at the Flywheel. It is 88.5BHP at the wheels.

Mine was done on a hot day so i might get it tested again when it is a bit cooler.

Cheers
joseph phillips

Joseph,
What year is your MG and where did you run the Pipercross cold air feed?
Frank

Joe,

To answer your original question, my B was dyno'd at 103Bhp at the rear wheels. BUT - the dyno was not 100% accurate at the time, but 'prety damn close'.

The engine has re-conditioned SU carbs's
K&N filters
an 1860 bore
a fast road head (pete burgess)
stock exhaust
stock dizzy (new)
Piper 270 cam


Its time I got it tested again as this was a year or two ago just after the engine was rebuilt. (The rebuild and test was done by Peter Burgess)

Richard
Richard

I achieved 104 equesterinos with a x-flow at 10.5:1, 1 3/4, Elgin ".017" cam, hardened and cross drilled crank, 60 over, 1:55 rollers, K&N,Peco, Aldon 2 dizzy. Fastest MGB 4 lunger I've ever had the pleasure of driving.
vem myers

Joseph,
Question: How does a rolling road test give both rear wheel AND flywheel horsepower figures?

I'm curious because I too have an MGB that registered 88HP@5400rpm at the rear wheels on a chassis dyno. My engine formula differs dramatically from yours however. Only 9:1 compression with .020" overbore, dual HS4s, Kent 717 cam, Mike Brown head with std. valve sizes, Maniflow LCB exhaust header.

I was told to expect a 25 or so HP drop from ENGINE HP at the rear wheels for "a car like a MGB", but that's a crude estimate. It would however work out very close to what you are quoting (113). How did they come up with a FLYWHEEL figure?

Kelvin Palmer

Frank,

My MG is a 71 GT. The cold air feed runs from directly behind the grill and you have to enlarge the hole on the right hand side (passengers side) of the radiator. You need to get the feed right at the front behind the grill of the gain is virtually nothing.

Kelvin,

My print out has the BHP at the wheels and at the flywheel. I think that they calculate the BHp at the flywheels by deducting a certain percentage loss through the transmission. I dont know exactly what that percentage is for a MGB but mine is 115.1 at the flywheel and 88.5 on the road. If you work out the percentage drop then it should be reasonably accurate to apply to other MG B's i would have thought.

Vem,

What benefits do you see from the hardened and cross drilled crank? Can you rev it a little harder?

Cheers
joseph phillips

My '71 was also done at Burgess'. It has a standard 1798 engine and camshaft, 25D4 distributor (with contactless set), standard carbs and exhaust manifold with a Burgess "Fast Road" cylinder head and K&N filters. After much fine adjustment, Peter got just over 90 bhp at the wheels. Before the head was changed it was about 67 bhp. As Mr B. says, the most gains are to be had in the head. Not bad for the money.

Mike
Mike Howlett

I might be imagining this but I seem to remember the chap I used telling me that the clever rolling roads calibrate for the friction losses to work out the flywheel bhp by spinning the wheels in neutral?
Steve Postins

This thread was discussed between 03/06/2003 and 04/06/2003

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