More Power from 1275?

[dunketh]

I was really happy with my 1275 engine ...until... I had a go in Packedup's Midget.
The midget was completely standard running the 1098 MG engine with twin carbs, standard exhaust and 295 head.
It seemed quite a big faster than my 1275 mog!

I know my engine is good, holds good oil pressure and has bags or torque and its quicker than my old Minor 1098.. but.. why isnt it as quick as it should be? (granted I know the Midget is lighter and more nimble)

I'm running an HS4 carb on a mini combined inlet. The carb has a Mini 1275GT needle in it as I thought this'd be a good a match as any.
My fueling is spot on as shown by the plug dusting and general running.
Can it really be just the fact I have a small carb and sh-not good minor exhaust system?

Will bolting on MG carb and inlet combined with a bigger bore exhaust make that much of a difference?

Just want to know really. The price of exhausts being astranomical I'd have to make my own regardless so it probably wont hapen. I'm just curious.

[bmcecosse]

That carb will be limiting somewhat - MG inlet with HIF 44 carb will make a difference. Next mod is to search out an MG Metro head with the bigger inlet valves. The cam would also benefit from upgrade to MG MEtro cam - but that's an engine-out job on the 1275. The Spridget is a lot lighter than your Minor - and also sits closer to the ground which makes it 'seem' faster too!

[Stig]

Well the Midget is lighter but it'll feel faster still as your bum's only a few inches off the ground.
As for getting more power out of your current engine I'd start with the exhaust - it's restrictive even for a standard 1098. I noticed it when just changing to a larger bore silencer on a 1098 and still using the original pipe temporarily.
Next (well, probably the same time in practice) I'd change to a separate inlet manifold as the exhaust heat is well known to reduce the inlet density.
After that you could fit a larger carb to get a bit more top-end power but the HS4 will manage quite a bit of power if the rest of the system can flow the gases in and out.

[Pyoor_Kate]

Aye, changing the exhaust and the carb will probably help. My 1275 (not brilliantly well as it was) was noticeably strangled by the standard mog exhaust and (in my case the standard) carb. Changing over to the HiF 44 and the larger bore exhaust certainly made a real difference.

[Kevin]

Can it really be just the fact I have a small carb and sh-not good minor exhaust system?

Will bolting on MG carb and inlet combined with a bigger bore exhaust make that much of a difference?

Answered your own question really although some improvement can be achieved by using an alloy inlet and splitting the exhaust section from inlet section of the manifold.

[Packedup]

I'm somewhat worried - The Midget is hardly quick, and nowhere near running right! The air filters resemble tarmac more than paper, the plugs are grotty, the whole thing is out of tune... And it's quicker than a 1275 Minor!?

That's just not right.

The 1275GT Mini put out approx 64hp IIRC using an HS4 on the cast "hot spot" manifold and a not great exhaust sytem, so I wouldn't say the inlet side of things is the bottleneck right now. That exhaust is going to be wreaking havoc though, the carb will be set up for a free-er flowing exhaust as will the dizzy, as well as simply being far too restrictive.

I've got a spare Marina/ Metro cast manifold if you want to chop the exhaust off and get the ESM twin downpipe bit (not cheap though I know) on it and run a decent system.

Alternately you could chop the inlet off as IIRC Vizard reckons it's basically the MG alloy one, just in cast iron instead! Wouldn't help your exhaust problems though...

[chrisd87]

The 1275GT came with 2 different power outputs depending on age, it seems. The early (pre-'74) ones had 59bhp, and the later ones had only 54bhp.

According to here anyway!

I suspect you need to get the car set up properly, and also investigate a decent exhaust. When I have the time and money I'm going to try and bodge the silencers from a high-performance mini system onto the standard pipe for my tuned 1098. You can also get performance back boxes and tailpipes designed to work alone but personally I want to avoid the 'big zorst' look if at all possible!

[Roni]

I had a full exhaust change to mine a while back. The std one was replaced with a 1½" pipe and a less restrictive muffler. The manifold is a cast Marina 1300 item which has a bigger internal bore than the std. It made a noticable difference in an otherwise std 1098. Generally the motor was a lot happier at open road speeds. I didn't lose the wonderful sound the Minor makes on overrun either. If it works so noticably on a 1098, the difference on a 1275 would be greater.

[dunketh]

I'm somewhat worried - The Midget is hardly quick, and nowhere near running right! The air filters resemble tarmac more than paper, the plugs are grotty, the whole thing is out of tune... And it's quicker than a 1275 Minor!?

Its the acceleration that was noticeable, I only got up to around 40 along that short road but it got there damn fast. The gear ratios seemed better too which is odd as you have the 1098 box.

Anyway, i've been looking at vacuum cleaners for inspiration. THe Henry at work has a nice long stianless tube attached thats a reasonable bore without being silly big. Couple of them pipes slipped together with an 'over acle' bend and generic silencer from Burtons and the jobs a good un.

Next time I see you, take the Minor out and see if its not just me being stupid.

[bmcecosse]

Put a 4.55 rear axle ratio in your Minor - with 13" wheels - and it will accelerate like a drag racer! If that's what you want ?

[Packedup]

Its the acceleration that was noticeable, I only got up to around 40 along that short road but it got there damn fast. The gear ratios seemed better too which is odd as you have the 1098 box.

The Midget box is the ribbed case one, but as standard it's a bit stronger and has closer ratios. That probably helps a fair bit.

Couple of them pipes slipped together with an 'over acle' bend and generic silencer from Burtons and the jobs a good un.

Just remember there's the bottleneck at the downpipe, so anything you fit after that still won't make a vast amount of difference.

Next time I see you, take the Minor out and see if its not just me being stupid.

You really don't want to let me loose to see how well a car goes!

I'm wondering about carb needle and spring. You might have a good part throttle mixture, but be leaning out when the throttle's opened (if I remember your carb/ filter setup). That'd give the right colour on the plugs but still mean things were wrong, but it's a bit straw clutching really.

[Kevin]

Anyway, i've been looking at vacuum cleaners for inspiration. THe Henry at work has a nice long stianless tube attached thats a reasonable bore without being silly big.

Hmm that and a length of scaffold tube and your sorted then

[Matt]

Hmm tell me what spec engine it is, and what needle is in there... i will stick it all in Winsu and tell you the outcome and compare the recommended needle with yours....

[dunketh]

Now you're asking!
Been a while since I put it in there! I'll have a look, cycled in to work today so cant look til tonight.

Engine: Standard 1275 Midget
Exhaust: Standard Minor/Mini Cast Iron Manifold
Carb: Single HS4
Needle: To Be Completed....

Another odd thing which may be connected.
On overrun I hear a whistle. Its like some kind of deranged dump valve. I quite like it so haven't bothered to investigate.
I used a new gasket when fitting the manifold and its all nice and tight. I also used instant gasket and paper ones when doing all the carb gaskets.
On the odd occasions when my manifold clamp isnt blowing - it still occurs.
Puzzler eh?