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MG MGB Technical - Suggested improvements for 73BGT

Hi folks,
I’ve had my 73 BGT for almost a year. It’s my first classic. I have very limited mechanical expertise which just about covers the very basics (e.g. to date the only work I’ve done on the car myself is changing plugs, replacing battery leads, replacing the speedo cable & a couple of dashboard switches).

Mechanically, the car has run reasonably well for the past year. From my limited knowledge, I can tell you that it’s a pretty standard 1800cc engine with twin SUs, “standard” air filters and oil cooler. From driving the car, the only issues obvious to me are:

1.It’s very slow to start from cold
2.It runs lumpy until it has been driven for 10-15 mins
3.It rolls/sways when steering (I’ve been advised that this is likely a problem with the rolls bar)
4.There is a clunk from the rear of the car when accelerating/braking (I’ve been advised that this is a knock on the rear diff – a common problem on GTs)

The body work is in pretty good shape – some rust showing through around the front/rear windscreen, some rust along the rear pillar seams. The main panels are all fine & there is no rust on the floors. The car was waxoyled by the PO, so the bodywork has been well cared for. The weather here in Ireland is simiar to the UK (i.e. 350 days of rain/15 days of sunshine!!).

The car has been off the road for a few weeks (it won’t start – I’ve checked plugs, fuel pump & replaced the points). I’m planning to have it serviced in a local garage that specialises in MGs. I’m going to take this opportunity to get a complete re-spray (from Damask red to BRG) and have a complete overhaul of the mechanics. Basically, I’m trying to get the car in as good shape as possible. I don’t have an unlimited budget, but am prepared to spend money where it makes sense. I'll be tackilng the interior myself (it's pretty much orignal, so is a tad shabby inside).

My question is this – what advice can you give me in terms of the types of mechanical mods that I should consider getting done to the car? I will be using the car most days for normal driving, so I don’t need/want huge performance mods as such. I am interested to know if there are some “standard” improvements/mods I could/should get done to the car.

I’d appreciate any advice you could give me. I did have a look through the archives, but a lot of the threads relate to high performance mods and most are a bit too technical for my limited knowledge.
Mark 73BGT

An MGB in good fettle should have no problems starting - hot or cold, and won't need *any* mods to allow it to run properly and reliably in any weather. Once started and whilst warming up particularly in very cold weather it is true it won't run as well as it does once fully warmed, but you shouldn't drive *any* car hard until it is fully warmed up anyway. When you say 'lumpy running' it makes me think you are overchoking it, which is very bad for fuel consumption but more importantly it washes the oil off the bores and rings and greatly increases engine wear. The choke is a continuously variable control and must be gradually eased in as the engine warms, using the minimum amount for smooth running on light to medium throttle. This should only take 15 minutes/a couple of miles or so. My roadster needs full choke to start, but immediately it fires I push it back half way, then gradually the rest of the way until the temp gauge gets towards the N. By contrast the V8 needs full choke to start *and* fior the first few seconds of running, gradually eased in after that.

If it won't start your first step should be to clip a timing light with an inductive pickup onto the plug leads and coil lead just to check they are all flashing when you crank. If not you check the LT side of the ignition for voltage and points operation, if so you check the timing is about right (about 10 degrees BTDC), fuel is available, and it isn't flooded. For these last two remove a plug after cranking for a bit. If it is wet it is flooded - push the choke home and crank it with the throttle wide open until it fires. If there is no petrol smell there is no fuel coming through - does the fuel pump tick when the ignition is first turned on after being off for several minutes minimum? It should smell strongly of fuel but not be soaked, in which case the problem is more likely ignition.

Whilst a garage that only deals in modern cars won't have a clue what to due with points ignition and twin SUs (nowhere to plug the computer) even some so-called classic specialists may not be able to set them up properly, but will charge you £50 an hour to do so. You would be far better off (in all senses of the word) and get much more satisfaction working through the ignition and carbs yourself setting them up. For this you will need the Haynes Manual as a minimum, the Leyland Workshop Manual is preferable, and there is lots of advice on-line. You might like to glance at my own humble offering - http://www.mgb-stuff.org.uk
- and click ' Spanners' then 'Ignition' (always setup the ignition first) and 'Fuel'.

The MGB *does* roll a lot compared to modern cars, and always has done. However it also has very good road-holding despite that. Any problems with the anti-roll bar would be an MOT (depending on which bit of Ireland you are in) failure - unless it has been completely removed, and not all had one fitted anyway. Yours should have, a 73 had a front bar but not a rear bar.

Diff clonks can affect all MGs with the later tube axle, not just GTs, although the GT only ever had the tube type. It is 'cosmetic' rather than anything else, and again there is online advice on correcting it like at http://www.mgcars.org.uk/cgi-bin/gen5?runprog=mgoc&a=&p=emg/emg010302.html
Paul Hunt 2

hello ive had the same noise from the back of my car,there is a bush which connects from the roll bar to the chassis .you will find that the rubber is perished ,its a job you can do yourself
daz

Mark-
Since you want to keep your performance modifications modest have installed at equal depth lead-free fuel compatible three-angle valve seats and three-angle 214N alloy Austenitic stainless steel valves with chrome plated stems and stellite tips (don't panic, they may sound exotic, but they're easily obtained and not very expensive), tapered (bulleted) valve guides, a set of the highly superior Fel-Pro Teflon-lined valve stem seals on the intake valves, 6" diameter X 3 1/4" deep K&N aircleaners, richer needles for your 1 1/2" SU carburetors, and a 1 3/4" Peco exhaust system. This will get you started with a relatively small investment and you'll be both surprised and impressed at the improvement. For better handling, have installed a Panhard rod on the rearaxle and heavy-duty valves in the front dampers.
Steve S.

If you would like to reduce the amount of annual maintenance your car needs, purchase a pertronix electronic ignition kit. You can switch to electronic ignition in about 15 minutes and not have to worry about bad points and condensers. No, its not necessary, but if you're not 100% comfortable adjust points and you don't own a dwell meter, its the easiest route!

Jeff Schlemmer

Mark,

You are obviously performance minded and the intent of your post is to "improve" the car, but a re-spray to BRG, which can be pricey, is inconsistent with your purpose.

Save your money on cosmetics and put it into mechanical refurbishing and sensible performance mods.

I prefer BRG too, but it is difficult to do a quality color change. Keeping close to original will preserve the value of your classic.

Keep your classic in that rich and dark Damask Red, I say, and spend your coins on go-fast goodies.

Just a suggestion.

Johnny
John B

Thanks for the advice folks...

Paul,
I take your point about the choke - mine needs full choke to start, but I do release gradually (the car will cut out if I release too soon). Most of my driving involves a 6 mile round trip to and from work, so the car never really gets a chance to warm up properly. Maybe this is something I will have to live with. On your advice about the non start problem, I'll follow your advice and let you know how I get on. BTW, you have some great tips on your website - even for a non-mechanical novice! I don't need an MOT (there is no mandatory government testing here in the Irish republic for cars > 30 years old)

Steve/Jeff, I'll definitely be pricing some of those mods you proposed. I was thinking about the K&N filters already.

John,
You're probably right about the re-spray. Maybe I'll concentrate on getting the performance sorted before I go spending money on a re-spray.

I'll keep you all posted on how I get on - thanks again.
Mark 73BGT

Mark,

If slow warm up is an issue you may want to consider fitting an electric fan and removing the mechanical fan from the water pump pulley.

Steve and Jeff have come up with some good performance mods but get the car running correctly as Paul has described before you start doing performance mods.

David
David Witham

Hi folks,
Took your advice & decided to get the car running properly again before looking at perfomance mods.

Paul, you were right on the money about a properly set up car. Following a good service, the car is running better than it ever has. The mechanic traced the problem to a faulty distributor rotor arm. He's given it a good service. The lumpy running seems to have been addressed by a combination of adjusting the carbs & adding some carb cleaner. It's like driving a different car. I'll drive it as is for the next couple of months before deciding if any mods are really neccessary.

Next job is to tackle that diff clonk...

Thanks again for all your advice.
Mark 73BGT

This thread was discussed between 07/01/2006 and 14/01/2006

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