Fuel's Gold

After upgrading the carburettor, exhaust and air filter the car initially went well. I had plans to have it properly set up on a rolling road to really get the best out of it but unfortunately it developed a peculiar stalling issue. The car would perform well under heavy throttle application and light throttle application but would really struggle in between the two. So much so that going along at a constant pace was impossible as the car would stall and then pick up again quite violently as the power dipped and then returned. 

Further investigation under various load levels revealed that the problem was intermittent - intermittent but happening most of the time as opposed to intermittent and happening only occasionally. This ruled out anything as rigid as ignition timing. The most obvious solution was fuel supply. Given that the newly installed carburettor was believed to be in good working order the fuel pump seemed like the next logical component to look at. 

The fuel pump on the Mini is driven by the camshaft and works by moving a small diaphragm up and down to pull fuel from the fuel tank and provide enough fuel for the carburettor to feed the engine. In short, it turned out that the fuel pump on my car had been replaced at some stage in the past - not uncommon, it is 20 years old after all. However, it had been replaced with the wrong pump. An aftermarket alternative designed for the 998cc model. The 1275cc engine originally came with the larger fuel pump. The aftermarket, smaller, cheaper pump is capable of providing just enough fuel for the hif38 to power the 1275cc engine but when I upgraded the carburettor size it demanded too much.

So it was time for a shiny new part! 

At around £50 the proper SU fuel pump wasn't the cheapest way to rectify the problem. I could have installed an electric pump for about £35. For simplicity of installation it's hard to argue with the mechanical option though.

The new part on the left is quite a bit bigger than the old one, which was quite reassuring when I compared the two side by side.

 Before I had realised the fuel pump was the issue I'd tried adjusting the mixture screw to no avail. It didn't solve the problem because technically there was nothing wrong with the mixture. The SU carb allows you to set the mixture at idle and then the profile of the needle within the carburettor takes care of the air/fuel ratio further up the rev range. The small capacity fuel pump seemed to perform fine when the car was idling. It gave a false impression of the fuelling overall though so a correct adjustment would have been hard to achieve. With the new fuel pump installed and a tweak to the mixture the car ran right again!

Now it's MOT time again. That came around quickly..

The Quest for Power

I'd always toyed with the idea of increasing the power a bit. The 1275 non-Cooper models for the most part came with the hif38 carburettor and quite an easy way of getting a bit more power is to fit the larger carburettor from the hif range, the hif44. To buy them new is silly money, luckily there are plenty around as they were used on many different vehicles.

To compliment the new carburettor, a new exhaust manifold, inlet manifold and air filter were purchased.

The difference in size can be seen here. On the left is the hif38, and the right the hif44. The simple theory of more fuel in, more exhaust gasses out smoothly carries on when the shape of the exhaust manifold is considered..

The replacement manifold, as well as being lighter than the old one, is also a better shape. The 'LCB' or 'Long Centre Branch' exhaust supposedly increases torque over the standard manifold.

Quality piece of kit!

As my car is a 1994 model with a catalytic converter I needed to make a piece to fit between the end of the new manifold's Y-piece (seen at the far end of the pipe in the above picture) and the cat itself. I used the flange cut off the old exhaust and bent and welded a new short section in to bridge the gap.

The new carburettor fully mounted up on the new inlet manifold.

All fitted into the engine bay nicely.

The next step is to get it rolling road tuned properly. It's running at the moment and certainly feels like it's got more grunt than it did before but to really get the best out of it the rolling road is next!

Back in black.

The wheel arches were looking a little sorry for themselves - rough around the edges and wearing a few scars from their initial fitting. So in the garage/workshop/paint booth/storage area/anything else it needs to be until I somehow manage to afford to have a large work area this week... I got on with the job of prepping and painting!

Painting is a tricky task. It's a fact often overlooked until a rushed job results in a bad finish but with the right guidance a decent finish can be achieved using modest tools and equipment. Sadly the budget doesn't yet stretch to a professional set up so spray cans were the order of the day. 

Preparing a surface for primer requires a 'key' for the primer to stick to. The idea being that if the surface is completely smooth before you begin the primer won't want to stay where you're spraying it. Roughing up the surface ever so slightly provides bumps and ridges, a bit of texture to aid the process. 

At the point of the above photo it's probably quite normal to be having second thoughts about the mess you're potentially making. 

A few coats of primer. It dries quite quickly and providing the spraying action is as smooth as possible it gives a smooth, even covering. 

A very fine grit sandpaper will smooth out any minor runs/lumps and prepare the primer for the next stage. This is over 24 hours later though, having allowed the primer to dry thoroughly. 

Lovely, glossy black! For a spray can job they've not turned out badly at all.

I've used a small finishing strip to sit between the arch and the body. Purchased for around £1 per metre it just gives a nicer finish than the edge of the fibreglass and provides a little rubber buffer to achieve a better fit against the body.

That's all for now!

Time for a new clutch

The clutch on this car had been contaminated by the oil leaking from the oil seal on the primary gear. There's a post about that here. At the time I didn't change the clutch plate. I'd hoped the clutch slip would be over soon as I'd stopped the oil leak.. no such luck! As it turned out the damage had already been done. So my Saturday afternoon task (a mere three months after my last post - oops) was a clutch change!

The trouble with changing the clutch isn't the clutch itself - it's all the other bits of machinery and whatnot in the way that have to be removed first. And as charming as the Mini is, the engine bay isn't exactly spacious. Bruised knuckles, fatigued finger tips and grime-covered forearms are pretty much guaranteed every time there's a job to do in the under the bonnet. But.. a little while later and after a few expletives the clutch and flywheel assembly was out.

Even though having the clutch and flywheel assembly out again made me think deeply about the beauty of hindsight, it did allow me to check the oil seal work I'd done. Every cloud has a silver lining.. I suppose.

With the pressure plate removed the clutch plate itself is revealed. Oily and slick. As the job of the clutch is to provide friction these are two pretty bad qualities to have.

A smear of leftover oil can be seen on the friction surface below. Oil where there shouldn't be oil is about as useful as a calculator in a Spanish exam in this setting.

So for a lovely, grippy and friction-filled time a new clutch plate saved the day.

 

A few more words of wisdom you wouldn't want your grandma to hear and a bit of struggling later and it was all back together. 

With the test drive complete having experienced no discernible clutch slippage I think the day could be declared successful! 

I'll get around to painting those arches sometime..