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MG Midget and Sprite Technical - 1500 cylinder head

Hey guys,

Im looking to get my cylinder head uprated. I have my original cylinder head bolted on the engine and it needs converting to unleaded. I also have a new head that has had the conversion done to it. I already have the peco exhaust system and will be fitting a fast road cam once I have had the crank balanced and toughened.

Where is my best bet to either exchange the two heads for one that has been flowed with uprated springs and the like or to get one of my heads uprated?

Thanks in advance for your help.

S J Dodd

I may be totally off base here (I usually am,) but I am pretty sure the 1500 can take unleaded without modification. I thought they came with hardened valve seats from the factory.

Also, we had a tech session with our local club this past winter about porting heads, etc. and I seem to remember the instructor talking about how the 1500 head flowed pretty well as is, with only minor smoothing needed that can be done at home. He warned that excessive porting and polishing on this particular head having worse results than doing nothing at all.
Lee Fox

Simon others will know better than me about Peco manifolds and exhaust

If you're using your car mainly for road use then I'd strongly recommend you're careful what cam you use

I've got a 1275 and so know less about 1500s but I wish my car had a standard cam instead of the very mildly altered cam it came with

My power band is narrower and higher than on a standard car so is not as useful on the real world roads as a standard cam would be

Also starting and tickover are not as nice as with a standard cam

If you're after a track machine then sorry just ignore this post
Nigel Atkins

I think there is something wrong with your cam timing
With a mild cam you should get a wider power band and keep a reasonable idle.
So either it has to be tuned or there is something wrong with the setup.

So Simon as a A-series guy no tips from me other than go for it and have fun
Onno Könemann

Try Jigsaw Racing in Corby, they do a lot with the 1500 engine.
l snowdon

Hi Simon

If you are uprating so much then a well modded leadfree head is a must and will compliment the exhaust, cam and filters. A very good extra is to fit heat shields for your carbs and maybe duct cool air to them as well.

P Burgess

>>Try Jigsaw Racing in Corby<< No, don't, I would not recommend them

- the cam in mine is more of a regrind mongrel type tick over and start aren't bad just not as sweet as when I had a standard Spridget

Present Midget had a rolling road set up last month and just under two years ago when I got power and torque print out (nothing on paper last month and I think the equipment dials were over optimistic)
Nigel Atkins

Hi Simon, The 1500 engine is all about great low and mid range torque, at which it excels due to its really long stroke (same bore as the 1300). At any given RPM the piston velocity is very high due to its long stroke. What it is not good at or very happy at is high RPM for the very same reasons. The unit really feels ready to change up as soon as you get to 5000 RPM if you regularly take it past that then the life expentancy of the bottom end will diminish. No doubt you can buy fancy big end shells, blue print the engine, balance everything ..... to improve things but fundamentally the unit is not set up for high RPM. I would certainly not go for a faster cam as you will loose much of that great tourque and not really be able realise the benfits higher up the rev range. Unlike the A series the standard manifolds are not that bad on the 1500 so you wont see the big gains by swapping them out that you do on the A series. One of my favorite mods though is to ditch the standard twin rear silencers and fit an MGB back box, works a treat you just need to roll up some sheets steel spacers to accomodate the larger bore of the MGB box at the join. Hope this helps and doesn't ofend anyone racing 1500's cheers Ben
Ben Brown

Thanks for your help guys, I am going to be getting the big end balanced and toughened and am also rebuilding the engine completely although I am not willing to put the time and money into a complete blueprint.

I was only going to get the fast road 83 cam as I thought I would be able to improve the top end without significantly reducing the low end torque but it appears I was wrong! I am not looking for a full bore racer but something a little bit better than the standard engine. I already have the peco exhaust system and will be fitting K&N's to the twin SU's and figured the next stage would be to improve the cam profile. Obviously I would need to improve some other parts of the engine as well to be able to withstand this.

I may have to have little rethink though. Any more ideas would be welcome!!

Thanks again.
S J Dodd

I have followed a similar journey to the one you're on ie moderately uprating a 1500 for fast road use. My 1500 seemed to benefit significantly from relatively minor inlet & exhaust matching and a general tidying up and smoothing of the inlet manifold and the head casting itself, but retaining standard size valves. This together with well set up carbs with uprated needles for the better flow has given me a really nice torquey but very responsive engine.

My experience plus what I have read previously on here suggests that the 1500 benefits a lot for relatively little cost from general 'breathing' improvements.

s lowiss

Don't want to hi jack the thread but I am staggered at Nigel's comments

The A Series engine loves being cammed even IMO a 286 which is considered fairly hot is a very drivable cam in a road vehicle and when you allow it to do it's job by revving its fantastic. I think Onno is correct you must have something seriously wrong Nige.

Regarding the 1500, I have no experience of this engine at all but I find if something sounds right it generally is and the post by Ben sounds spot on to me!
Bob Turbo Midget England

Bob sorry to shock you :)

Most forum post tend to be short and excluding qualifying remarks, I'll add them here

I expect it's a matter of taste and use

I prefer lower revving and torquy engines and/or set up and I use my Midget as an everyday and touring car (to hilly places like Wales)

To my style and taste of driving the warmer cams I find are not as nice

Personally I don't really like keeping the revs up high or waiting for a Midget to build the revs (tho' I did briefly own a Honda S2000 with a power band of 7,800-8,500 rpm, rev limiter at 9,000)

I don't think there's much wrong with my engine as at both rolling road set ups no real comment was made about it (good or bad)

First rolling road power figures were about book original but with higher rev band (approx) 4,500-5,300 as opposed to IMO the more useful 3-6,000

With a fuel tank that only holds about five and three quarters gallons I find driving round at high revs for sustained periods to be awkward in parts of the country where petrol stations are further apart and not open long hours

Don't get me wrong I don't always drive around like a Sunday aunt, some people in my club believe that I travel everywhere at breakneck speeds just because I like to open up when on tours

To summerise I'm sticking with my opinion, my first Spridget had a standard cam and that's nicer to drive on the road in real world situations - sure if I had the money I'd have different cars for different situations but I can (now) only afford the one car that best fits the predominate driving situations

Different people, different views and opinions but hopefully I not said anything wrong (when I find I have I always apologise and correct it)

Different (correct) opinions give choice

I've no technical knowledge (easy to tell I know) but I do have experience of owning and everyday driving of classics for many years
Nigel Atkins

If the RR gace you the factory power figures with a higher power band then there is something wrong.

Either a complete mismatch in parts or bad cam timing or what ever.

it may run nice but it is not reaching its full potential

My 1380 with flowed rimflow head and 731 cam and 45 weber idles somewhat irregular a 1000rpm.
But there is power from 2000 rpm comparable with a std 1275 and above 3500 until 6500/7000 all hell breaks lose (in the good sense that is)
and can deliver 30mpg (35 can be done but is no fun at all)

I am not trying to piss you off or take a piss at your car.
I am only saying this becaus i want you to have the most fun with your car.
Onno Könemann

I had a 1500 head gas flowed with new valves etc form Peter Burgess which I was very pleased with. He actually ended up uprating the block as well.

E R Brown

Hi Eddie

Is that the one with the Piper 270 that went like a scalded cat for some unkown to us all, including Piper, reason?

P Burgess

Onno don't worry mate you are not upsetting me

Yeap there probably is a mismatch in engine parts but I bought the car as having a recon engine with only 50 miles on it and;

progressively run it in for the next 2,000 miles

oil and filter changes at 100, 1,000 and 2,000 miles

HGF at 7,000 miles

engine out at 14,000 for g/box

engine out again 9 months later to put right clutch

shed loads of my wife's money having been spent on it since buying it

So,if the engine seems OK then it's run as is

To be fair the first RR was with the old carbs (that I wanted to change at the very start of ownership), old dissy, old g/box and tubed steel wheels - altho' the bhp line was diagonal the torque was pitching around the close figures between 4,100-5,100 rpm

Last RR I wasn't offered or asked for a print out and the numbers on the dials were significantly higher but seemed optimistic to me as it's regular driver

I'm not one for numbers other than as a rough guide or starting point for progress but I want the car to feel right

You can never have enough power on a perfect day, on a perfect road, the rest of the time there's more often than not more in reserve than you need

I like a car to feel fast not at 160 mph or 90 mph but at 60 mph because that's were most of my driving skills, licence, pocket or nerve lie

I've done my bit for insurance statics and was very lucky not to have seriously injured anyone so I'm wise after the event

Go safety fast everyone
Nigel Atkins

Best not say anything otherwise this could become a very long thread! :)
Robert (Bob) Midget Turbo

The OP reached his conclusion a few posts back so go on

have a laugh / get it off your chest

disagree / agree ????

as I've typed before there's usually more than one view
Nigel Atkins

It's a can of worms Nige mate, not worth the effort, as you say we all have different opinions and have had differing experiences.
Robert (Bob) Midget Turbo

Shame, I was curious as to what you wanted to say (about my post)

If you think I'm missing out or for some reason you think I'm talking out of the back of my head you could email me

cheers, Nigel
Nigel Atkins

Shame, I was curious as to what you wanted to say (about my post?)

If you think I'm missing out or for some reason you think I'm talking out of the back of my head you could email me

cheers, Nigel

whoops, only wanted to add a ?
Nigel Atkins

Nothing in particular Nigel. Simply surprised that you think a standard set up is far more desirable in a street car than something a little more adventurous. As I said it can be a can of worms but simply skimming 60 to 100thou of the cylinder head of a standard engine will give a nice increase in torque and subsequent power, at what cost? Practically zero!

That must surely be a good thing isn't it?
Bob Turbo Midget England

My fault Bob I've given the wrong impression - I'm not against modify/customising/tuning up cars – most of my cars had at least some slight modifying

My Midget is full of upgrades and updates to make the car more reliable and useable

I don't find say medium to hot cams particularly nice in otherwise fairly standard cars especially for everyday cars and was just warning Spridget newbies that may not have consider this

I know a lot of posters here are able and enjoy being mechanical with their cars (not me on both counts) but clearly not all can and they would have to pay someone else to do the work so need to consider what they ask to be done to get it how they want it first time

If you have to pay others to do the work then even modest power gains can be expensive let alone the parts costs, sure if a part needs replacing then upgrade

Skimming the head – if the head is already off or needs to come off fair enough

The head on my car was skimmed as part of the HGF rectification (does that count?) and could have been skimmed when the engine was reconned (assuming that engine is the one in the car) or before that

I did mean IMO you don’t necessarily need a lot of power to have a lot of fun and my experience is that more power needs higher speeds to get a corresponding level of fun, I appreciate that lots are better drivers than me but with the roads as they are tend away from high speeds

It’s also a matter of getting the balance right, sometimes for some people they can do too much to their car and take it away from when they had the car at the optimum for their enjoyment of the car

If you’re at ASDA Day or November NEC (SBDR) pop over and I’ll take you out (if you’ve got insurance at the NEC you can drive and tell me what you think of the car)
Nigel Atkins

What is ASDA day?

I see your point and it is a good one. The old saying that a little knowledge is dangerous is very true. I think we have evidence here right now (Prop) that doing too much with no experience and simply listening to a couple of tonnes of garbage can create an unusable monster.

We are in total agreememnt!! :)
Bob Turbo Midget England

Heyyyy, we'll agree on agreement but disagree on total

ASDA Day is a charity event in Liecestershire, more chance of seeing you at NEC Classic Motor Show I help with SBDR
- - no photos of me or my cars here (I'm too ugly) but my wife features in a few of the presentaions and in one her previous car, a Copen
Nigel Atkins

the best motto for tuning
"tuning is always a compromise between what can be done and what should be done"

and yes i totaly agree that you don't need a lot of power to have fun!
a standart 1098 will do just fine for that
Onno Könemann

Thanks for all the information guys, really I just want a bit of tweaking to make a reliable lump that wont leave me looking stupid on the rare occasion that I end up at the lights with someone that needs taking down a peg or two (obviously staying within the speed limit ;))

Everything will be balanced and I am now thinking of doing some flow work to the head as it is already off. Still not sure about the cam profile though. It's a tough decision that may eventually come down to money as always!
S J Dodd

Mine is pretty standard now - and there's nothing I can't leave behind at traffic lights - or even on a bendy road (and, when she's really working hard, on a straight too!)

The great thing about the 1500 is that, if it's balanced and the timing is really right, then there's not a whole load more you need to do if that's all you're wanting to do. Obviously, other little things like lightening the flywheel, changing the diff, putting lead in your right foot - and, even just adding higher rated petrol ...! Just, make sure you don't waste too much time wheel-spinning ;)

Rach - waves bye bye to the Lotus which lines up regularly in Wisbech for it's beating ... :)!

No comment on the traffic lights drag races

The best tuning for a lot of classics is the much needed full and regular servicing and maintainence and regular use

My Midget is now set up for 95 octane so it'll be interesting to see what difference I'll get (with the full electronic dissy) when I next use 99 octane

I'll try two tanks full of 99 and then go back to two tank fulls of 95 to compare performance
Nigel Atkins

LOL Nigel - it gives me good practise for autotesting - and I never go over the speedlimit (Angel sign!)

To go back to the original question ... I forgot about this website I found awhile ago, which is of great use and interesting reading - and which goes through all the changes you can make and what effect it will have on your engine:

I daresay that there are those who will knock it, coz it's a Triumph one, but, the engine is anyway!

May I recommend a frequent visitor to the BBS? Peter Burgess will do you a very nice head and I am sure he will be happy to advise you on mods to suit. My 1500 was modified many years ago produces 98 bhp on Peters RR with great torque, spend some money ensuring the engine is well balanced, you can also do some usefull work youself to help the engine last. This includes cleaning up the con rods (see moss tuning manual for details) Photos to follow :)

C Bintcliffe

Before and after!

C Bintcliffe

My shiny new bits!

C Bintcliffe

Nice shiny bits!!

Thanks again for all your help on this. I have a couple of weeks to work on the baby from next Friday so hopefully I will get a lot done then! I am sure I will come up with more questions for you guys then...
S J Dodd

This thread was discussed between 16/07/2010 and 02/08/2010

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