9 replies to this topic

[mr cooke]

Hi all . I am looking into getting afew more bhp out of my 1275 engine , I already have a lighter fly wheel , twin carbs and LCB. 

I have being looking into fitting a turbo but its to much work , cutting bulkhead , changing pistons , x pin diff etc .

So now I am looking into other ways like camshaft , cylinder head mods. 

can anyone please give me any advice on what cam to use for road use and what cylinder head mods .

Thanks Chris . 

[KTS]

have a read through this thread - most of what you need to know should be covered

 

http://www.theminifo...5-metro-rebore/

[Benoit_Dupont]

Well, appart from air filtrer/needle/exhaust, aka stage 1, any serious mod will require Big bucks for moderate gain, unfortunatly on A séries.

Indeed a little more agressive cam is as far I would go without looking at getting the gearbox reinforced. But i may be conservative.

[Cooperman]

The key to performance improvement is the cylinder head. It needs to be fully gas-flowed with larger inlet valves (35.6 mm).

Without really well-done head improvements there is not much to be gained for other mods, especially a more aggressive cam. Unless the head can flow more mixture in and exhaust gas out, a more aggressive cam will simply not be able to improve top-end power/torque, but will cause a loss of bottom end power & torque.

[rally1380]

Listen to Cooperman ^^^^^^  the head is the key to A series power before anything else.

 

After that, cam and rockers would be my next spending point as you already have the breathing side sorted (assuming they are twin 1.5" and not 1.25"???)

[mr cooke]

Listen to Cooperman ^^^^^^  the head is the key to A series power before anything else.

 

After that, cam and rockers would be my next spending point as you already have the breathing side sorted (assuming they are twin 1.5" and not 1.25"???)

Thanks for all the reply's . The carbs are 1.25 do you thinks this would make much difference .

[rally1380]

Listen to Cooperman ^^^^^^ the head is the key to A series power before anything else.

After that, cam and rockers would be my next spending point as you already have the breathing side sorted (assuming they are twin 1.5" and not 1.25"???)

Thanks for all the reply's . The carbs are 1.25 do you thinks this would make much difference .

In a word..... Yes.

Those size carbs are more for small bore engines and came on the coopers. The larger bore 1275's produce more power with twin 1.5" su's.

But.... That's not to say you need to rush out and buy some. A well tuned HIF44 (1.75") carb on a decent manifold works really well and is a much easier setup to live with on a day to day basis.

Couple the better carb setup (whatever you choose) with a good quality modified head, a cam and a better rocker setup (assuming you currently run standard sintered ones) and you will see a significant power and more importantly, torque increase.

Also, depending on what final drive ratio you have, if you swap it out for a shorter ratio the car will feel significantly quicker off the line with no actual power increase. It'll kill your top end speed, but that'll depend if you want to cruise at 70 on the motorway all day, or thrash a good twisty B road?

Another huge performance gain... Or rather something that will effect your power to weight ratio is the overall weight of the car..... Ditch anything heavy and the car will accelerate quicker... Free performance.

Hope this helps?

Edited by rally1380, 20 August 2019 - 06:25 PM.

[Fast Ivan]

You would be amazed at what a difference to performance it makes by making sure it’s in A1 serviceable condition, has had a proper tune up and a has a good suspension setup

[Cooperman]

Most owners of classic Minis talk about getting more power, but what they really want is better acceleration rather than more top speed. Better acceleration can be achieved by mild engine modifications as discussed above, but also by lowering the final drive ratio (FDR) to a 3.44:1, lightening the flywheel and matching all the components by way of a careful and accurate engine build.

 

Don't be afraid to rev an A-series when cruising. A 1275 engine will rev at 4000 rpm or just above all day long and it is how those engines were used 'back in the day'.

 

We drive old and relatively slow classic cars because we like the retro driving feel, so when cruising it is fine to use 4000 rpm, which is just under 70 mph in 4th with a 3.44 FDR. In fact 70 mph is 4200 rpm. Lowering the FDR does not really reduce the maximum speed, it just means the maximum speed happens at higher revs and a lower FDR can actually increase the max speed as it enables the car to pull further into the drag curve, but at much higher revs. My 'S' will rev to over 7000 rpm in top, but 7000 rpm is just under 100 mph.

[mr cooke]

Thankyou to everyone who has taken there time to reply .I have a better idea what i am going to do . Think i will start with the cylinder head .