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MG MGB Technical - How to subsequently improve performance

i have an US spec 78 MGB and need more performance. I like torque engines, so I am not so interested in peaky power. Car is really too slow. Engine seems worn out to me too, although I didnt measure anything.

Currently I have 1 single carb.
THe following small steps have already been taken:
1 REmove cat. converter and replace this with upgrade exhaust system
2 K&N air filter
3 All the emmission controll stuff is removed.
4 Vacuum advance by pass on 3/4th gear is removed.

Now I have the following step in my head:

Exchange engine for 1950 stage 2 engine, with 2 carbs.
Questions: Does this have major impact? Should I take balanced engine?
What carbs would be best? What impact on performance?
What cams would be best?
Better go for 2100 cc engine?
Any need to change ignition/distributor?

I also thougth for a moment to do a V8 conversion but my local MG mechanic said it is a lot of work and is going to cost a lot more money. Which sounds strange to me, since the engines are quite cheap available.

Anywya, All suggestions are welcome,

Rik
Rik

The answer is simple, if you like torque then fit a 3.5 V8.
The mathematics are straightforward,torque is in simple terms a direct consequence of the amount of fuel burnt in 1 revolution. Hence therefore twice as much fuel is burnt by a 3500 than a 1750 in one revolution, not rocket science is it!!!
Bob (robert)

I would reccomend getting the car to something like the equivalent UK spec for the year (strip all the emissions gear, install twin SU manifold and carbs) and see where it gets you. You should be able to pick up the carbs and manifold fairly cheaply off ebay. I should think it will feel a lot better with that done.
dave

I have the privilege to owned two MG. One GT daily use with a 1950 Aldon engine, stage2 with HR270 camshaft, this engine, with 80000 km env. is superb, powerful, flexible, never fail, a real pleasure. One roadster hardtop v8 conversion, racing mod, 3.5 slightly tuned, there no possible comparison with a four banger. The v8 engine is really powerful, but require, imho, good handling and good braking and much money. The choice is not easy.
Regards
michel

Rik,
It sounds like your car needs a bit of tlc. Before rushing to get a bigger engine and all the extras, see if you can get a drive in a standard car that is well tuned, preferably with a good, flowed cylinder head. I suspect you'll be amazed. Unless you never want to change gear, standard engine has plenty of torque for the car; sure, not like a V8, but then nothing is. The 1800 is still a world away from being a peaky engine and it has a great balance of torque and eagerness.
Steve Postins

The MGB, even in it's best stock state, like my early 5 main I bought in the sixties, was never really a road rocket. If you're looking for performance and reliability, a V6 /V8 conversion is the way to go. I think you'd increase your performance right now, just by adding twin SU's and finding a stock exhaust manifold for the early cars. Don't assume the engine is worn out--US spec cars were slugs once emissions control was mandated. You probably have the Zenith still installed--it's not a bad carb--but it was installed to control emissions, and performance suffers. I would avoid installing a weber setup--the SU's are just as good...and easier to set up. A crossflow head will give you a substantial boost but $$$$. Give the car a good tuneup before you do anything else.
R. L Carleen

Answering your questions a bit more directly than my last post:
The bigger bore engine will give you a large improvement over what you have. I've just looked at the figures for your car and can see what you are missing:

US 1976-79 MGB 62.5bhp@5000 72lbft@2500
UK spec MGB (about) 92bhp@5400 110lbft@3000

Some power will have been won with the work you've done so far, but some (how much?) will be due to the low compression pistons used.

Twin SUs are the outright winners if you want low end and mid-range performance.

The engine builder will advise on the cam best suited for torque and that engine.

Yes, you will want, at the very least, to have an early distributor with a more suitable advance curve, or even better an hour or two at a rolling road and a custom curve set for the engine.

I can't say for 1950cc vs 2100cc but the former is a less radical change to the block, so probably more reliable. Remember that either way you are not going to get a long-legged autobahn cruiser. That needs changes to the gearbox/differential ratios. If that's what you desire, the V8 really is your best bet but be prepared to open your wallet wide.

Steve Postins

Rik
I used to live in The Netherlands. And before that in the U.K. whilst I was there I had a road spec engine built by Motorbuild. It was only bored out to 1840 cc as I have heard that you can get problems with the block. I don’t have the car now so I can't give you a complete spec. Motorbuild often visit classic car shows in The Netherlands and have a regular van delivery service too. I would suggest that you contact Grahame Davis via the following web site for more information on his engines. http://www.moto-build.co.uk/
One thing you will need to set up the engine correctly is a rolling road. I never found one in either The Netherlands or Belgium. I hope someone else can lead you to one.
BTW I lived in Eindhoven.
Cecil Kimber

Rik: The 1950 stage 2 will double horsepower at the rear wheels and offer great torgue. From what you wrote I believe it would meet your needs.

You should purchase the book "HOW TO POWER TUNE NGB ENGINES FOR ROAD AND TRACK" By Peter Burgess to gain an understanding of the best power improvements.

Also visit engine builder Chris Betson's web site http://www.octarineservices.fsnet.co.uk
He builds B engines to various specs, including 1950, using Burgess heads.

IMHO the 2100cc engine does not offer enough improvement over a good 1950cc to justify the greatly increased cost.
Terry

uh, that is "How to Powertune Mgb Engines...."
Terry

Okay...sigh... http://www.octarine-services.co.uk
Terry

Hi Guys,
Since this is my first question on this BBS, I am amazed by the number of replies, so fast. I submitted membership today, so you are going to read more questions.
Thanks a lot for your helpful information.
I am not going to do V8 conversion, I have seen enough reasons and opportunities to go for stage 2 1950 cc.

I am going to read the book: HOw to powertune MGB.

PRobably then:
Install double SU, see what this brings.
Install 1950 stage 2 engine. So I am going to see who are good,recommended suppliers.
And then: get it properly tuned on rolling road.

And for Cecil (Spain): I live in EINdhoven as well.

rik

I have one question about that thread. P.Burgess excellent book page 15 tells to be able to provide 95HP
versus 65 as standard at the back wheels for MGOC club race car with twin SUs 1,5" and standard cams plus 1,625 inlet valves. Who knows and who can tell more ?
Many thanks.
Renou

rik,
Before you commit yourself to 1950 cc, if you have not done so already, go to the archives and search for "whippet" in both the MGB Technical and MGB General sections. You won't have an overwhelming return in either, but I suggest you pay attention to the comments of Roger Parker - a well-respected contributor in the past.

Wayne
Wayne Pearson

Renou,

That engine is "blueprinted", that is, all the parts are carefully chosen, matched and fitted to minimise the power losses within the engine. This is not a cheap "fix"!!

Rik,

The starting place should be how you drive the car - out and out horsepower is traded off against low down torque as the state of an engine's tune is increased. This is offset slightly by increasing the capacity of an engine, but a fast road 1950cc engine is a different beast to a fast road 1860cc engine and delivers its power in a different way. Roger Parker has likened the 1860 to an eager whippet versus the 1950 as a powerful bloodhound! Certainly the 1860 will beat the 1950 away from the lights even if it does get overtaken a mile down the road.

The V8 is incomparable but is expensive - if you want to go that way, sell your car and buy one already done - you will never recoup the costs of the conversion in an increase in value.
Chris at Octarine Services

Chris: I don't understand why an 1860 would beat a 1950 off the line, given the same Piper 270 cam in both. Am I mistaken in believing the extra capacity of the 1950 produces more low to mid-range torque than the 1860?
Terry

Rik,

I know of a good dyno in Goes (I live in Belgium, not too far from the border)

Drop me an email if you want the address etc.

Groeten,

Alexander
Alex @ university

hi
Ive just had my gt tuned and tweaked a little by a local chap in this area who seems to understand the mg engine "Peter Edney" and what a diffrence my gt spec is as follows
Stage two head
1860 block
normal cam
twin 1.5" su carbs
k&n filters
peco mild steel 2" freeflow hdr system
This should prove to be a fun set up with not to many holes in the wallet
Servo for the brakes is next
Have fun
Richard H
Richard H

Hi Richard ,
I ve always read infos about PECO HDR on this BBS but did you previously switch from the factory cast manifold or not to adjust the two parts together ? Answer is welcome please .
Renou

Rik. Your fellow country-man Frank de Groot runs a dual fuel V8, he is in Holland at the moment, if you can contact him (his E mail address can be found on the MGOC BBS posts), I'm sure he will let you have a ride and persuade you that V8 is the way to go...expensive yes....but well worth it !

Mike
M Barnfather

Rik. You may wish to discuss this matter with Peter Burgess who can be reached through this website. I have dealt with him in the past and found him a wonderful source of both information and modified cylinder heads. I have also dealt with Chris Betson and have been quite happy with the results.

Your "US Specification" (actually a North American specification--the Canadians got stuck with it too) not only is a low compression engine, but the cams used tended to be "soft" in the sense that they wore rapidly. I have pulled several of these over the years and found the cam lobes badly worn. Thus, while I never found the original engines to be too bad, a good quality rebuild is a much better performing engine that the late US versions. Were I in your position, I would e-mail both Chris and Peter and ask for their recommendations.

Yes, you will need a different advance curve on your distributor which was curved for emissions reduction rather than performance. Les
Les Bengtson

Rik,
Reading very deep into what you said leads me to believe that a rebuilt motor with only one bore oversized and the motor backdated to older specs (or build to Euro-specs) will give you exactly what you want without going overboard. ....and I build V6 powered cars.

Try to find a few people in a local club with older stock versions or UK spec versions who are willing to let you take a ride with them (if they know how to use the throttle all the way to the floor!) or allow you to drive a 90 to 100 BHP car. Just this alone will allow you to see what the difference is in an earlier non-US spec car.

We may have less costly gas, but lord help us, we went through the 1970's at speeds of less then 95kph!

-and engines/emmissions to match acceleration.


Safety fast (Just not in a US Spec late model stock B)

-BMC.
BMC Brian McCullough

Hello Renou
I had an aftermarket freelow before but not a very good one .The peco hdr system comes as a complete kit and fits straight on but you may hit one small problem you will find that the flanges on the inlet manifold are thicker than the new freeflow manifold by about 5mm this is overcome in two ways the easy option is to cut some washers in half and use this to make both surfaces level this is the most common method or if you want to go all the way grind down the flange on the inlet manifold to the desired depth. I have to admit Renou i opted for a good mechanic who understood the problem to do the whole job including a retune afterwoods you are looking at a max of 4Hrs at around £40per hour to have the job done, plus around £225 for the whole system And to finsh renou the mild steel system sounds very nice with twin 1.5" su carbs and k&n filters
Regards
Richard H
Richard H

Renou,
I use Maniflow LCB manifold and one box big bore exhaust system. Very good efficiency and nice sound. Concerning the difference of depth between the flange of inlet and exhaust manifold I have welding a small piece of steel to the exhaust manifold for equalize the depth.
Regards
http://www.maniflow.co.uk
michel

Don't consider 2,100; I would prefer 1,860 to 1,950 both in the interests of useable performance and reliability.

Rover V8 is the way to go though - no question.

NJSS

BGT V8
R V8
MGA 1600 Mk I Roadster
Nigel J S Steward

Hey Guys, I have been reading the links and I am wondering when was the cut off for US MGB's impotade to the US with the low com. motors? I have a 1974 crome bumper produced in Feb. would that be concidered a britsh spec or US. I bought it 2 months ago and it does run great an does not have a smog pump or Cat.
Youre reply will be apriciated.
Thanks,
Miguel Q.
Miguel

Miguel. I am not sure, exactly, what you are asking. There were several specifications for the MGB. Probably the most important was the "North American Specification" which was the US and Canada. The Canadians got stuck with what the US demanded. There was also a "home market" specification for the UK market and some other specifications for less popular markets. (For instance, the UK spec cars had headlights which dipped to the left. The NA spec cars had headlights that dipped to the right. French spec cars had headlights that dipped straight downwards. And, there were others.)

If you have a 1974 car, you most probably have a North American specification car having an 18V, low compression engine with two SU HIF-4 carbs. You should have a single charcoal cannsister, a non vented gas cap, a vent from the fuel tank to the charcoal cannister, vents from the carbs to the cannister and a line from the cannister to the valve cover.

The definitive work on this subject is "Original MGB" by Clausager. It might be worth seeing if your local library has a copy (mine did). If not, they can obtain a copy through inter-library loan. Les
Les Bengtson

Guys,
Great to see so much response on this topic. I have read it all and lots of other articles,
I have set my mind on following to improve the performance, but still with some questions, see below:

1950 cc stage 2 engine: MGOC also delivers these, does anyone has experience with them?
TWin SU, 1 1/2 of 1 3/4 : From what I read, 2 x 1,5" should be sufficient, anyone can confirm this?
modified distributor.

Thanks,

Rik
hpm rik

2 x 1,5" is plenty. I've used them on my 1995cc without problem, but you will need to get advice on needle selection. I can't comment on the MGOC blocks, but knowing the stresses needed in going to 1950cc and above, I'd prefer a bit of individual care and attention for the engine from the likes of Mr Betson (see his comments above). I have to add, speaking as someone who has both an 1800 Stage 2 and a fully worked 1995cc, I'd go for an 1868cc for the money.
Steve Postins

Thanks Steve.
Is there enough space to mount twin SU, as in the US specced b's the brake servo unit sits quite in neighbourhood? Any need to use special small, powerdestroying pancake airfilters?

Rik
hpm rik

Rik,

I've bought an uprated 1950cc engine from Chris.
Works beautifully, no oil consumption (except at a constant 5500 rpm, which occured in Holland btw).
And Chris will help to select the components etc so you have an engine that will suits your wishes.

Groeten,

Alex
Alexander M

Rik. K&N make a filter for the 1.5" carbs that is designed to work with the US/NA spec brake booster. I do not know if the engine would produce less power due to the conical design. It actually looks like it would provide more air flow than the standard filters I am using. Les
Les Bengtson

and you could swap the NA booster out for a remote booster and early master cylinder so that the booster was out of the way!
Chris at Octarine Services

This thread was discussed between 13/02/2005 and 04/03/2005

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