Welcome to our resource for MG Car Information.



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 Midget and Sprite Technical - 1275 Performance upgrade


I have a 1275 midget which I am considering giving a bit more umph, but do not want to get into the realms of mega bucks or expensive upgrades. I think that the engine is basically OK although it is showing signs of oil burning when cold and on over-run (valve guides / oil seals)

I recently put a Kent 266 cam into a 1098 mini and fitted a midget head and twin carbs - this made a considerable difference. As the 1275 is starting from a higher benchmark, would the 266 cam also have a similar effect on the 1275 or would it be less noticeable? The car already has an LCB manifold and twin 1 1/4" SUs. The head I believe to be standard, so presumably a stage 2 or three head would be beneficial, but at a significant cost. I think these retain around the
Alan Drain

Well... 1st how much do you want to spend, a
2nd what are you willing to do yourself. 3rd and most important what do you want to do with this new engine as in what do you want to get out of it.

Without knowing the above... A good place to start would be swiftune... The SW 05 camshaft is nice but he has add on packages that make a hi performance rebuild very doable
Prop and the Blackhole Midget

A decent head is a good idea. you can also get it converted to run on unleaded if it doesn't already. Mine runs a cooper 's' spec head, standard cam, twin 1 1/4 SU's and an LCB and we got 75 BHP on the rollers.Thats 10 BHP more than standard so its noticeable. A cam change is an engine out and then you might as well do a full overhaul which starts to get costly. I got mine from Slark Race Engineering who fitted it and put it on the rollers all for about 600 They are in Amesbury wilts
Bob Beaumont

Paul Walbrans site gives good general advice on upgrading your engine, well worth a read.

Alan cotterill

the engine isn't only way to improve a car's performance plus with yours you've put that it isn't perhaps in it's best condition so you wont be build up from the best of foundations and to make it work harder as it is doesn't seem the obvious course

the first level of tuning is regular full and proper servicing, maintenance and repair of the whole car

more efficient running of the whole car as it is now will bring gains

a Spridget with a mildly or even highly tuned A-series engine wont be that quick on paper or compared to modern cars but feels worlds better

one of the major elements that will make your car travel quicker and it's largely transferable to your future cars is driver training, knowledge and experience

what will make the car travel quicker follows a similar path youd think of for safety driver, full maintained car, brakes, tyres, steering and suspension, lights, visibility

as for engine, well full regular servicing and change of parts where required (such as HT leads, rotor dissy cap), changing to electronic ignition might help more so if you renew the dissy as well, rolling road set up with Peter Burgess where you can ask at the heads he builds

but its no good flogging a sick horse
Nigel Atkins

Thanks for the comments above. Nigel, I believe that the problem with the engine smoking is head related as the pistons and crank were refurbished about 15 years ago and the car has not covered significant miles (prob less than 5000 miles) since.

I think my desire for a bit more go comes from the fact that I race a 1600 K series caterham which does go well, and have considered a K series engine change, but don't want to change the midget that way - I am a bit of a purist in that sense and would rather just improve what I have. I accept that it won't ever go like the Caterham, but I don't want to be racing it anyway - that's what the Caterham is for!

I am looking for a bit more grunt for overtaking and spirited road driving - not out and out speed machine. I guess I'm looking to spend under 1000 and take the point about improvements in handling etc.

Getting back to the point, will the 266 (or SW5) which I think is similar, give noticeable improvements on the 1275 as it did with the 1098?

Alan Drain

I've never had a 266 cam. But my 276 cam is fantastic for overtaking. However it is coupled to a high compression 1330 with decent exhausts and a single 1.75 SU. It runs on unleaded and ticks over at 1000rpm but doesn't do much below 2,500rpm it's still very comfortable to drive in Central London traffic.
G Lazarus

Then, of course, hi-lift roller rockers make a difference, and then, and then, and then, and then, there's even the work that MED do on A-series engines, to take them to 1496(or so) - LOL - where do you stop???

Perhaps a good start is Vizard, but then, with minis - you'll know all that!

There's plenty of head places around, both Peter Burgess and Peter May being very highly recommended around here. Exhaust helps - Magic Midget is also a very good supplier.

All joking apart in the first paragraph - sometimes I'm lucky enough to drive a car that is fitted with a fairly mild cam, but with the hi-lift roller rockers, which means that the power range is all the way through, which is much more drivable in traffic than the one that I drive with a fast road cam and standard rockers.

End of the day - you pays your money, you takes your choice - but, if it's just for power overtaking, then, keep the cam not too hairy (266 will give you the improvements you had in the 1098), and put a decent head and exhaust system on, together with checking over the bits you've mentioned, and you'll have a great car with enough grunt to overtake most things and run up to well over the speed limit :)

Yes, 266 is a worthwhile cam for road use. It is at the smoother end, works well with high lift rockers (though they cost a lot) and certainly a big improvement over standard. I haven't tried 276 directly but have had equivalents.

If you don't mind partly lumpy idle then the next thing to look for is whether a cam results in a gasp around 2000 RPM. Look for a cam which is smooth here on full throttle (rather than die when you put your foot down), even if not at its best till 2500 or more. 276 should do that I would expect.

Best approach for road mods is to decide your budget then work out the package of mods which give best value. Otherwise you can incrementally add things and end up spending heaps more than intended. And a lot of fun of course, but always the nag that you didn't want to go that far.

The thing with camshafts is that a lumpy cam costs (more-or-less) no more than a perfectly docile one - so the extra BHP is free so long as you make the right choice and get the combination you want first time.

Problem with cams is that one person's meat is another's poison ... what I think is smooth & wonderful another will think is horribly lumpy and uncouth - and vice-versa. So I tell my customers the best approach is to weedle a drive in a car with the cam you are thinking of and decide whether that's what you want or not.
Paul Walbran

another solution would be to get all your kicks on the race track by getting a bigger engined track vehicle so that there loads more seperation between the two as par James Hunt style

I've no idea how much extra overtaking ability the extra cam would give you on the real world roads perhaps overs could say but I'm not sure how near to your goal it would bring you but it's your car and money so you chose

I used to have cars that could overtake a line of traffic easily and at the same time once had another car that I thought was quicker than it actually was and found it lacking in overtakes because I was used to so much more, I found when I got a slower car I was less frustrated because I accepted the overtakes weren't possible

I would now sometimes like more power to get by stuff in my Midget but it's a compromise against having a pleasant car, just means planning the overtakes more and a greter sense of achievement to get by one car let alone two or road load

my mate insisted on taking me out in his old man's saloon with 600 'talks' and he overtook a very long stretch out line of cars and it didn't excite me, or frighten me it was frakely mundane (perhaps too easy) perhaps it's my age

I love to overtake but you learn on the road not matter how much power the oppitunities are limited - missed my mate Saturday he called round to take me out in his 4.3 ex-hillclimber Westie, areoscreen only (no side screens or helemets, it's a Westie not Caterham :) ) now that gives you a sense of speed even at legal speeds and even in that we're sometimes stuck in traffic

drop the top on your Midget wind the windows down get to the twisty back roads with less traffic to worry about overtaking
Nigel Atkins

That's a cool idea Paul :)

Alan, if you're at MGLive in June, you're more than welcome to have a drive in lil Blue and see what a silly hairy cam can do! That should put you off for life :)!!!

I tour in Europe quite often. Stelvio Pass a couple of times up hill & down dale, highways & by-ways.
Ferrari test track - Fiorano once for fun.
MED HT cam (& head) & roller rockers. Smooth tickover.
Suits me.
A Anstead

I'd be inclined to pick up a copy of Mr Vizard's book which will tell you pretty much everything you need to know about A series modifications.

I've always gone for a total approach to tuning - not always to achieve outright power, On a road (1275) Midget for instance I'd advocate a rebore to +0.020 (1293), new bearings, lighten and balance rods, crank and flywheel, fit a mildish cam (270/276 carefully timed in) a gentle job on the head - gasflowed, larger inlet valves, raising the CR to around 10.5:1 with 1.25 SUs electronic ignition and an LCB exhaust. That should give around 80-90bhp and a useful increase in performance without huge power and torque increase such that the transmission would be at risk...


James Bilsland

Finally, James has hit the nail on the head (no one else has mentioned it yet): for more power the most important thing that you can do is increase your compression ratio as far as you can (depending on available gas/octane).

Porting, and cams (a 266, while good for a small 1098, but maybe for the larger 1275, a 276 / SW05 is the best match for power without giving up too much low end drive ability).

x2 on the balance. Best $100 you can spend on a rebuild. Helps any engine rev smoother.

Norm Kerr

wouldn't go for a rebore unless you absolutely have to. It unnecessarily shortens the life of the block IMO.

My A series was equipped with an MG metro head with a slight skim (can't remember comp. ratio), twin 1 1/2 SUs on ported manifold and LCB with large bore RC40. MGB needles (can find them if useful) were apparently perfect.

I did the head & manifold myself as per the vizard book, and it gave a decent 75bhp and 88lbft on a RR.

Total cost was less than 70 quid, including a brand new silencer.

Blew up 2 A series gearboxes with that engine, and it's currently chewing through dad's gearbox as it's in his car now.
Rob Armstrong

Thanks everyone for your comments. I have the Vizard book so will do a bit more research on rocker ratios. I think I will have to get the head off and get a measuring stick to see what I have got in respect of CR's and head thickness to see if it has already been skimmed. The point is whether I can work with the head I have, or bolt on a new exchange.

I take the point about overtakes - some of the fun of the midget is just driving along a country lane with the roof off - whether at 40 or 70 - it's still great.
Alan Drain

Sorry, have to disagree with Rob - what seriously reduces the life of blocks is when old pistons break and scrap the bore... There is no reason why you can't get 75000 - 100000 miles out of a rebored motor with modern rings and decent pistons - 1293 leaves you with options to go +0.030, +0.040 +0.060 or go down the 73mm/73.5mm/74mm big bore route.

The better quality pistons you use on a tuned engine the better IMHO - especially if you are going to play with the CR...

James Bilsland

on top of the stuff I've put in my other posts things that have improved the overtaking ability of my 1275 Midget that I can think of now are,

123 (fully electronic, new) dissy very good through out the reve range, clean pick up,

LCB, which you've got,

rolling road tuning (and correct needles) - not all rolling road tuners are equal (I mention this particularly as you mentioned Minis) - I found Peter Burgess very good indeed (and much better than another A-series specialist)

not proven yet - but I think my selection of engine, g/box and r/axle oils has helped, I might be wrong and/or fooling myself but I have previously owned cars that could overtake very sucessfully so know what quick pick up feels like
Nigel Atkins

>> Sorry, have to disagree with Rob - what seriously reduces the life of blocks is when old pistons break and scrap the bore... There is no reason why you can't get 75000 - 100000 miles out of a rebored motor with modern rings and decent pistons - 1293 leaves you with options to go +0.030, +0.040 +0.060 or go down the 73mm/73.5mm/74mm big bore route. <<

that's fair enough :) Though perhaps unlikely to get a piston to explode, that's something to bear in mind. Does it make that much difference to power, having an extra couple of CC? I know the mini guys keep going straight to 1380, increase in torque but no more sensible rebores left.
Rob Armstrong

1293 does not increase the power a lot
1380 gives you a sensible amount of additional torque.

But I will not go to a 73.5mm bore with my new engine (current one is).
Mostly because I think it is a shame to do that with a std bore block, it is not allowed in any form of competition I might want to do.
And I don't need the thrill on 1st startup again to see if the rear oil passage will hold!
Onno K

This thread was discussed between 23/04/2012 and 25/04/2012

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.