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MG MGA - Winter Project

The trouble is when you enjoy playing with the car mechanics as much as driving it you come to the point of running out of the obvious things to do. I read Dominic's ditty about the spring pan and bushes and thought I could do an overhaul. I had a look today and mine are fine.

There is a bit of backlash in the diff so I guess I could try and address that if I can get to grips with how to do it - I have had it apart before to change to 3.9 and change the sun gears so that is one potential task. The other is tweaking the engine. It's a stock 1800V, plus the 5-speed with all the MGA bits hanging on it. It also has my home designed and made stub stacks and goes like a rocket. I was just wondering whether, for a bit of fun, to pull the engine and do a light bit of improvement such as a modified camshaft etc. Not looking for anything spectacular, just a project to improve my skills while the winter weather precludes driving activities.

Thoughts on light engineering projects please. Anything to gain by changing the camshaft without going daft?

If I go this route my radiator will be available for overheaters to trial.

Steve Gyles

Heated seats?
You have to add an alternator, but the accuspark one looks just like a dynamo at a very reasonable price.
dominic clancy

The trick is to have 2 classic cars. One will always require repair...
A Bowie

Got the alternator Dominic. I have always wanted to do a Morgan 3-Wheeler but they out of my price bracket now, unless someone out there can source me one. My late Father-in-Law had 3 at any one time in the 30s. One can only dream.

Steve Gyles

Steve: why not get the Mrs or next door neighbour to go into the garage and adjust something or remove a bit. As they gets more adept they could become more and more devious, making the job of getting it going again even more challenging.
Watch out for "I drained the engine oil" - could be a bit late when you find that one.
Graeme Williams

I assume that you have a standard camshaft in your engine.
It is actually a pretty good performer for a standard MGB motor but some gains can be had if you fit a Piper BP 255 cam or at the most a Piper BP270.

These both work best (especially the BP255) if you have had some cylinder head work done, for example if you fit the Peter Burgess Fast Road Head.

It then starts to get a little expensive and you still may only end up with 10% more power than you have now.

Bear in mind that you would be better advised to fit new tappets and ideally new rockers and pushrods so that everything beds in properly. Which all add to the expense.

I would probably leave any cam change until you have decided that you are going to go for a tuned cylinder head and ask someone like Peter Burgess which is the best option first.

A supercharger works really well with a standard head and cam and probably would be the easiest way to tune your engine.

Dominic is the man to ask about this.

That is the way I would go if my engine was in a standard state of tune but because it has a high compression cylinder head and a 3-bearing bottom end, supercharging is probably not the best option for me.


c firth


A potential task would be to check the play in the differential input pinion gear. When I took mine apart due to a leaking seal I discovered that the shims had been shredded.

Wear on the camshaft thrust plate can mess with timing and a steady idle. It is a cheap part and relatively easy (but time consuming) to replace. While you are at it you can put a timing wheel on the crank to check timing alignment with the camshaft. With better camshaft timing my operating temps have dropped about 10 degrees and gas mileage improved.

If you still are looking for things to do you would be welcome to drop by to help me with a very long list of to do's. Just a short 10 hour flight from Heathrow to Seattle.

John Backman

Piper 270 is a great cam for cruzing in a fast road car. Ive been running that in my 3 main B engine for years now. Love it. Mga carb set up.

On a 5 main 18v B dont you have to pull the motor out of the car to get the oil pump gear out? Other wise you cant get the cam out of the block.

I cant remember now...but Ido remember tryingand the ealier than 18v motors you could change the cam in the car...but Ithink the casting changed enough on the 18v that you couldnt wiggle it out. Anyone do one lately?

I just cant remember.
Steven Devine

I think as John said it may be the diff I have a look at. I think it will take several readings of the Manual Section H to begin to understand the process. At least I have most of the tools and gauges. It's something I should have checked when I changed to the 3.9. At the time I just swapped the sun gears to take my splined shafts. I (wrongly) assumed that the pumpkin I had purchased was otherwise well set up.

Steve Gyles

If it's broke I guess you have to fix it otherwise there are so many other things on the MGAGuru list that make the A safer or an easier car to drive.
Where in Hampshire are you ?
Roger Walker

Steven Devine, -- It is a fair amount of work to change a camshaft, but you don't have to remove the sump or the oil pump. You do need to remove the distributor drive gear, mostly because you have to re-index it after installing the new cam.

You need to remove pushrods first which with a bit of finesse can be done without removing any head bolts. Get the manifolds out of the way to remove side covers and tappets. Get the radiator out of the way to remove crank pulley, timing cover, tensioner, chain, sprockets, cam retainer plate, and finally the cam. Set crankshaft at TDC so the con-rods do not interfere with the cam.

If you think it doesn't want to come out past the oil pump drive gear, just give the cam a little rotation until the cam lobe clears the gear, and it will come out. It should slide out just above the body air pan. Pretty sure the cam comes out of the 5-main bearing engine in the same manner, as there are only three bearing journals on any camshaft.
Barney Gaylord

Thanks Barney....

For some reason I just remember having an issue removing the cam on an 18v....but it was so long ago...I cant remember the details. I think Im chasing my own tail here. Ha ha ha
Steven Devine

How about fitting Barneys combined Headlight flasher/ Dip switch relay Steve?
Not a big job by any means but well worth doing.
It is a brilliant upgrade.
The upsides are as follows-

When the headlights are switched on, you can dip the lights by just extending a finger and pressing the switch down once.
Another press and they are back on high beam.

With lights turned off the same switch then acts as a high beam flasher switch and it is surprising just how often you use this feature.

If you next remove the now redundant foot switch, you are then left with somewhere for your left foot to actually rest!

The one down side is that you have to drill a new hole in the dash for the flasher switch.

But I'm certain that MG would forgive you as they drilled a similar hole to fit their own flasher switch.

c firth


It's not something that interests me. although I have been known to flash my spotlights.

Barney's write-up is interesting. If I go that route I will probably lift the engine as an opportunity for a general engine bay and engine clean-up. It's only a leisurely morning job to get it out or two hours if I put my mind to it. I have not got anywhere near Dominic's 45 minutes so I won't even try.

However, I am still minded to check out the diff. I don't find the 1950s style of technical authoring easy to follow so I need to do a lot more research to fully understand the process. I spent 2.5 years of my RAF career writing the aircrew manuals for the Tornado (introduction to service in 1982), RAF Phantom F4 and Jet Provost; also the flight check lists and emergency procedures. So I know a little bit about ABC (Accuracy, Brevity, Clarity) and to avoid the other A - Ambiguity. Fortunately, having done my bit I had a professional civilian author at another desk to correct my English and grammar!

Perhaps someone has found some good YouTube instructional videos that may help?

Steve Gyles

Delighted that you have started this thread as my 3.9 diff is gathering dust until I am ready to fit it. I need to hear your experience before I start, as well as to wait for a duff shoulder to mend. I had an offer of a supercharger in the Autumn but the timing did not fit availability of funds.


That supercharger is still available, although I have sold two others in between...

dominic clancy

I have found what looks like a good video on YouTube for the Sprite and midget diff, which is essentially the same as the MGA. Not seen it all the way through yet, but looks promising:

Steve Gyles

Re Supercharger: thanks, but no progress yet with the other projects, so funds not available. Current Winter project is to get two duff shoulders working properly; without them it is really difficult to reach vital parts of the cars.

My winter project is going to be fitting the Moss Spax rear shocks conversion. I hope this will cure a strange clanking noise from the rear when negotiating deeper potholes, but I plan to do it anyway - but I will probably wait until the NAC spares show to get the kit at a discount! There are probably other jobs to do as well when I get under there ...... AB
A Bennett

This thread was discussed between 30/11/2015 and 12/12/2015

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