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MG MGB Technical - LOW END GRUNT

Hi,

How can i get low end grunt on my MGB GT '68.
I've read that fast road heads and big bore exhausts only really increase grunt at high revs but i don't thrape the car much over 3000rpm. I was thinking of getting a peter burgess ecotune head which says it increases power by 30% at 3000rpm. Can anyone recommend any fairly cheap things i can do <£300ish
Mr MG

fibreglass everywhere!

Stuart Robson

Try a V8 engine.

Mike
Michael barnfather

You could research porting a cylinder head and then attempt it yourself. I think this is about the only real way of increasing torque short of a camshaft change etc. It has been done with a dremel and concentration before....

You might try K&N air filters and a change in needles, but these won't be noticeable i'd have thought.

A camshaft change can be done with the engine in-situ but if you can't do it yourself = .

basically you can have what you want, but only if you throw cash at it...

~PHIL
Phil

According to the Factory Special Tuning manuals for the MGA and early MGB: "If most importance is placed on initial and middle range acceleration an improvement of 2 or 3 bhp may be gained in the lower ranges by fitting camshaft Part No. 1H603 [later book says part # 484184]." I beleive this cam was originally fitted to the Riley 1.5. Cam specs are Intake 5/45, Exhaust 40/10; valve lift .322". "Top end performance will only be slightly impaired between 5,000 and 6,000 rpm. If desired, the head may be tuned by port polishing as laid down in Stage 1."
So maybe the Econotune head and this cam?
Marvin Deupree

Mr. MG-
A Peter Burgess Econotune head and a Piper 255 camshaft should do nicely for a low-rpm boost. However, that'll cost more than 300 UKP.
Steve S.

Never tried it, but theory suggests you could advance the valve timing with an offset woodruff key and bring the torque peak lower in the rpm range. This isn't an area I'm very sharp with, so maybe one of the experts could comment on the idea.
Matt Kulka

I think you'd want to retard cam timing to get extra low-end torque. Also running a larger valve clearance (which results in less overlap) will make it torquier at low revs, although I expect with all the clattering valves you'll be breaking valvestems before others, and for not a lot of gain.

Other small tricks include longer inlet manifold rams, smaller diameter but straight-through exhaust system, less valve lift (different rocker ratios) for better swirl...

Big tricks include: big-bore stroker engines with tall pistons, short rods and de-shrouded inlet valves; nitrous; forced induction; replacement with small block chevy... :o)

I reckon the cam as per the Special Tuning Booklet's stage 2 and a mild port smoothing plus overbore to +0.060 will get you what you want.

ttfn,
--
Olly
Oliver Stephenson

To move the torque curve to lower revs, you have to advance the cam timing. Also, shorter duration cam timing and keep the valve lift.

Wayne
Wayne Pearson

My apoligies re. cam timing, I must have my brain wired out of phase :o)

--
Olly
Oliver Stephenson

OK, now consider this.
MG builds a car with a 1 to 1 4th gear, then they give us a 3.9 final drive.
This is how you get 'grunt' .
This is why it was designed this way.
Low gears and rev's.
What are you afraid of?
Let it rev to 5500 rpm or higher. I have beaten many higher powered cars [stop light drag races] because they short shifted at lower revolutions. And they still don't get it.
I regularly rev mine to over 6000 for auto cross competition.
Ask any club racer how high they rev.
Back in the days when I crewed for a friend in a SCCA prepared MG midget, with a Huffaker 1098cc engine, he shifted at 7800 rpm, with the occasional burst to 8000+. Now this was a modified engine, and I wouldn't recomend higher than the redline.
But use it!
Safety Fast
Dwight
Dwight McCullough

you could try building your own intake manifold. Long narrow runners increase low end power and short large diameter runners increase high end power.
If you use a runner the same size as the intake port in the head and about 4" long, the power comes in around 2800 rpm and carries through to about 4000-4200 rpm,(my tach is real inacurate though).
Good luck- but remember, there is no replacement for displacement.(I am going the small block route)
Robert

Supercharge !
H O

You don't have to spend a lot of money to get low end torque. If you do your own cylinder head modifications you can get a big improvement without spending a lot of money. You will, however, spend a few really hot, nasty, noisy days with the die grinder.

My '66 B will pull top gear from about 1800 rpm to redline. It has fabulous low end torque. When I last rebuilt the engine, I had been studying Peter Burgess' book for some months. I ported and polished the head myself to his DIY spec and had my machine shop do a three angle valve job on the stock valves. Keeping the ports small speeds up intake charge and increases torque. Intake is the stock original HS4s with #6 needles and K&N filters with the intake cans removed. Exhaust is a crummy 3 into 1 header and 2" exhaust. probably no improvement over cast iron/Peco.
Cam is an Elgin regrind, which is very close to stock. I paid a lot of attention to camshaft timing and got it right this time.

Good luck!

Chris

Chris- Any advance keys? What were the Elgin specs if you have a second. I installed the, I think, " Elgin: .017" recommended by Doug Jackson on a cross flow 2 years ago: Jumps bad like a scalded cat from 1500 to as far as I dare. Vic
vem myers

Being of the era where both big blocks and sports cars filled my head with big ideas I did some pretty severe head work on a 67 B head--larger intake valves, polish and porting besides wholesale hogging out of metal inside, bench flowed and all that stuff. My cam was a stage 2 cam with a Weber DGV. After I got the carb sorted out--going up 2 sizes on the idle and main jets I was both frightened and disapointed. I had a top end that was beyond my desire or ability to drive my roads at, hilly mountains with way too many bad curves; but I had no low end torque. I installed an adjustable timing gear and knocked it back two degrees. I am now in love. Good top end and loads of low end torque. With my 5 speed conversion I could be going up a hill in 5th , step on the gas and pick up decent speed. It may be a way out for you. If you need any info email me. Good Luck. ED
edmund kulick

My 67 mgb gt has great mid range. Good power all the way but really strong from 3000 to 4000 rpm. - just where you need it. I accelerate well in overdrive at 65- 70 mph without need to shift down. I'm running low compression with the 5 port (cleaned up) alloy head and a mild Kent 714 cam with stock carbs.

The late model usa mg engine has all the low end umph. Low compression, very conservative cam, single carburetor.

Several factors to consider. If cam timing is retarded it will reduce low end power and raise hi rpm power. If you distributor has a late model or inoperative advance mechanism you may not be getting enough spark advance at low rpm. With a hi compression engine (not a 75 or later, smog engine) you should be able to advance the spark to get a noticeable ping. especially with 87 octane gas. Advance the spark until you get ping and then retard a smidge to avoid the pinging. Carburetor's could also be too lean or too rich at low range, - look in other messages re carb adjustment & repair.

Barry
Barry Parkinson

Vem-
Do you mean distributor advance or camshaft? I know I used an offset cam key, but it was just to set it to Elgin's specs. I can't remember which key I used. I also can't remember which Elgin cam I got, but it's on a card somewhere. I called them and told them what I was doing and they immediately said "you need the ---grind" and I did. It took a very long time to get my cam back, but it was worth it. Just call Elgin and they will set you up with what you need. They stress matching your cam to your engine and will ask exhaustive questions about your setup.
As far as distributors go, I am embarassed to admit that I'm running a rebuilt stock dizzy (25D?) and I don't even know if the advance curve is right. The timing marks are gone off my timing chain cover, so I mostly guess at ignition timing. I've been setting it this way since 1986 though...

Chris
Chris

This thread was discussed between 28/05/2003 and 02/06/2003

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