MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - increasing power

Hi people.
I am after your thoughts. I want to increase the power of my 1969 gt. I have been looking at the BB and now i am not sure about a few things.
1. how much bhp increase can i expect by doing head work, cam, air filter, exhaust.
2. i dont realy want to go down the super charger route as i would prefer to spend that amount of money on a new body shell rather than a go faster bit.
3. would i be better off saving my money selling the GT and get a MGC and play with that engine.
I am not quite sure which way to go at the momment so some wise words of people that know more about the posibilites of 1800 cc gt and what kind of increase in power for what kind of money ( i have a some money burnning a hole in my pocket)would be very welcome . many thanks in advance Andy.
andy

Andy,

Depending upon who you ask, you'll probably see anywhere from 20-30% with the mods you desribe, if performed correctly. Most importantly, however, is how much more powerful your B will feel. I've never bothered to measure my B's power in any sort of instrumented fashion with similar modifications. Rather, I just enjoyed the additional fun in every mile.

Have fun,

Barry
Barry Kindig

Barry,

That's what its all about, isn't it? The fun, I mean.
Paul Noble

Andy,

Come have a chat in the chat room on my site - I will be on at 10pm tonite (Monday)
Chris Betson

Andy-
If you mount a pair of 3 1/4" deep K&N airfilters and let Peter Burgess rework your head to his Fast Road specification, you should see an additional 25% more power @ 3,000RPM and 30% @ 5,200RPM. Add a Piper 270 camshaft to the Fast Road head and you should see a good 5% beyond that, plus power will fall off more gradually above 5,300RPM than it would with a stock camshaft. Add a Peco exhaust and you'll have yet more, perhaps another 5% at mid-range and at least 7% at the top end. With this setup it should wind merrily to 6,000RPM with ease. Add a Maniflow intake manifold and a distributor with an Aldom-modified ingnition curve and together they'll add 5% to both the mid-range and top end. Better yet, forget about the OE head and just go get a brace of Weber DCOEs and a Derrington cross-flow head and let Peter do his magic on it and you'll boost your mid-range power by 40%. Figure on a good 110HP at the rear wheels (not at the crankshaft) With all of this stuff, the only MGB that will be able to stay with you will be one just like it. As they say, Power costs. How much power do you want?

Peter also works his magic on MGC engines, too. As they say, there's no substitute for cubic inches. 180-200HP is possible and still have it streetable.
Steve S.

For instructions on more power be sure to check the V8 conversions Bulletin Board on this site.
Chris Jones

Andy,
Steve is very close to the mark as usual. I recently went down a simlar train of thought to you and am more than happy with the result. It is probably worth talking to Peter Burgess about your requirements - he really knows his stuff. I had him build my engine (bored out +060, fast road head, piper 270 cam) Ive got it on K&N's but just the stock exhaust. It is a really smooth engine now, and Peter measured around 105 BHP at the wheels - more than enough.

This is in a 1970 B. I would go that route again, rather than paying the weight penalty of the 6 cylinder C engine.
richard

guys thanks for the wise words, i think i will be having a chat with Peter Burgess. a quick question doesnt the tick over suffer if you put a fast road cam in. Also can you alter the position of the power band. There are not to many long roads in wales so i would prefer better 0 to 60 than top end.
while we are on the subject my 69 gt will get to 4500 rpm then the rev counter seems to stay around 4500rpm but the engine note increases but not alot. Any ideas? once again many thanks in advance. Andy
andy

Andy,

One of the cars we worked on locally ('72) had the same problem, where it almost "hit a wall" at around 4,500RPM. We changed the smog needles out for non-smog needles and the car was transformed! That isn't a guarantee that this will work on your car, as other factors can come into play(Especially the exhaust system.)However it's a step in the right direction, and a cheap one at that.

Sean
Sean Brown

Andy-
With the carburetor and ignition timing properly sorted, the idle with a Piper 270 should be little different than that a a stock engine. The Piper 285 will, however, result in a somewhat loping idle. Providing that you've got the carburetion and ignition timing sorted, you should not have to play with the throttle to keep the engine from stalling at idle. Remember: Always do the heads first. If you recam an engine with a stock head, you're likely to be disappointed. Your gains at high-RPM will usually be less than what you'll lose at low-RPM, and the hotter the camshaft, the greater the losses will be and the smaller the gains will be as compared to a milder camshaft.
Steve S.

Andy,

The 270 cam is meant to be very close to the original cam, so the power comes in at low revs. The 285 Cam may give more power but this would be at the top of the rev range, and at the expense of power and smoothness at low revs. A slight increase in bore will give more torque, which will help further with the power at low revs. The head work also acts to smooth out a lot of the lumpiness of the B engine at idle.

From experience my car now idles very smoothly at 600 - 700 rmp, with plenty of power at those revs to pull away strongly. I did have to buy another distributor though - since the original would not hold the timing. I just replaced it with a rubber bumper unti though (since these are still available new).
richard

sean
Thanks for the tip but my car is UK spec. Can you explain what the smog needles are? are they like the needles in your carb?
Has any body tried putting throtle bodys on a MG rather than carbs. If so will this dramatically increase the power or would i be better off doing the head mods, getting a piper 270 cam, exahust and filters and then splash out on a set of twin 45's. OH any idea how much the 45's knock your fuel economy.

ANDY.
andy

Andy,

I am running 1850cc, stage III head (44mm inlets), Kent 717 cam, HS6's, Aldon distributor, PECO manifold and exhaust.

Idle is very smooth - at 1500rpm. Seriously, the car idles happily enough at 1000rpm but is very lopey; lightening and balancing the flywheel does wonders for responsiveness but also works against you at idle.

How much power you get depends to a large extent on who measures it. 105bhp sounds a bit optimistic for a 270 degree cam, particularly with a rubber bumper distributor.

In my experience, every expert has a different opinion on what makes good power and what is good value for money tuning. Be careful! Some will try to sell you a 45DCOE, some will tell you HS4's are plenty big enough. Some believe in huge valves, some say that you should stay standard. Likewise with cams, exhausts, ignition and so on. Try a few experts and see where they agree. Be wary that you will spend more money than you expect - on 'little' things like 'uprated' distributors and sports coils and radiators and electric fans and special spark plugs, etc, etc.

As for country roads, what about uprating the suspension? You wouldn't need to accelerate as much because you wouldn't need to slow down as much for the corners......

Neil



Neil

Neil
Thanks for the advice. I am in the middle of making enquires from a few experts on what is the best think to do but its nice to here from people that have done these things and dont mined telling other people about the results of there efforts.
I am one ahead of you on the suspension. I am in the process of gathering all the parts needed to rebuild and uprate the front cross member.

PS all this info is good stuff. Its helpping me build a picture of what i want to do. Keep it coming. MANY THANKS EVERYONE Andy.
Andy

Andy, is that what that "Wales" next to your name means? hehehe

Probably should pay more attention before I start posting next time.

Everything you stated in your "wish list" sounds pretty good to me with the exception of the throttle bodies. Do not waste your money! As far as I'm concerned, considering the available manifolds and air filter arrangements, twin HS4's or HIF-4's are just about perfect for road use. You can go with a single DCOE to gain a little, (but spend a lot) and you can ask guy's like Bill Mertz how that combination runs..

But without a properly reworked head, anything you do to the rest of the engine will be compromised in it's performance. Believe me, I'm not just saying that because we do head modifying, it's because it's fact. Start with a good exhaust, the head, and then take it from there.


Sean
Sean Brown

Neil,

You are right, 105Bhp does sound pretty optimistic for a 270 cam. All I can say is that Peter Burgess measured this, and had been telling me he expected something in the 90's. It is possible that the rolling road was not calibrated properly. In fact Peter said at the time that I was welcome to come back after he had had it rebuilt for another tune up session.

I have no idea what 105Bhp should feel like, but I like driving the car and thats what its all about anyway.

Richard.
Richard

This thread was discussed between 17/12/2001 and 20/12/2001

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.