More Power Please

[davewhitrick]

Looking for any and all help for adding power to my Mog.

She's a 1957 2door (948) virtually untouched mechanically aside from a break servo fitted before purchase.

Had her two years now, enjoyed her on sunny days, been on holiday in her etc. But now, I want to try and give her a little more pep.

There are few underlying issues that i'll mention first. There is a nauseating whine coming from either the gearbox, diff or both. Not entirely sure. Also, when in Idle/Neutral it sounds as if the clutch is slightly engaged as when you depress the clutch pedal it goes quiet?

I'm looking to fix the noisiness, keep the original engine but up the power. Read a bit about Vizard and his antics, 1275mini heads, Maestro cam's? Tolerances/measurements for boring out cylinders are like chinese to me, not saying i'm averse to it but if you could explain it first I'd appreciate it.

Any chance that with the 948 a mk1 midget sort of output would be achievable? Anyone else tried to do something similar?

Any and all help is much obliged.

Cheers, Dave.

[Matt]

Hi Dave

I would strongly suggest you buy a copy of "Tuning the A Series" by David Visard and having a read of it.

99% of the tuning of the A series is improving the flow of air into (and combustion products) out of the engine.

The midget engine is exactly the same except its fitted with twin carbs and a different exhaust.

[MorrisMinor-65-1000]

There are few underlying issues that i'll mention first. There is a nauseating whine coming from either the gearbox, diff or both. Not entirely sure. Also, when in Idle/Neutral it sounds as if the clutch is slightly engaged as when you depress the clutch pedal it goes quiet?

Hi Dave,

Have you driven many other Minors? First gear has straight-cut teeth which are famous for whining. It's just the sound of the teeth landing against each other as they rotate - an inherent side effect of the design. Put loads of those little tapping sounds together and make hundreds of them happen per second and it adds up to a whine! Slop in the bearings would also contribute as the mesh tolerance would be a bit wide.
Can you be sure there's definitely something awry in you gearbox?

As regards the quietness with the clutch down, that's perfectly normal! The sound in neutral with the clutch up is the input shaft, layshaft and gear clusters rotating in all of their bearings. When you put the clutch down, the gearbox doesn't spin any more so the noise stops. Simples!

[bmcecosse]

Check for oil in the gearbox......Change it or top it up with engine oil. Likewise the final drive - EP90 for that. Easiest power improvement is a turbo charger - but DO NOT exceed 100 kg/h or the FIA will be after you....... Oh hang on - it's not an F 1 car! The best upgrade for a humble 948 is to separate the inlet manifold from the exhaust - to eliminate the 'hot spot' - this will give you the small increase that the 948 Midget has. Midget also has a straight through silencer for a tiny extra bit of power. Next step - larger 1.5" carb (with top quality air filter) on an alloy inlet manifold for a few extra horses. Next step - head and cam from a 1098 engine - skim the head by 60 thou. That plus larger carb/alloy inlet will be good for ~ 50 bhp - but at highish revs of course! Upgrade the front brakes to the later 8" drums before doing anything........

[davewhitrick]

Thanks for the replies everyone, much appreciated.

I have only driven the one minor so my experience is somewhat limited.

A whine has been present since I've owned her, normal or otherwise i'm not sure, but it seems to have got louder recently, I think... there might be a slight case of hypochondria involved.

Kept up to all Oiling around car which is why I can't understand it getting worse (if indeed it has).

As far as manifolds and carbs go, what car does a 1.5" manifold come off? 1098? And what designation does a 1.5" SU have (currently on original H1). What about a midget manifold with twin SU's?

Upon changing cam/skimming head/adding a bigger carb etc would the 948 gearbox and diff be suitable or would the gear ratios near changing?

Again, all help much appreciated!

Cheers, Dave.

[bmcecosse]

If your carb is an H1 - then are you sure the engine isn't actually an 803? The H1 was fitted to the 918 SV engine - and the 803 OHV. A 948 should have an H2 SU - later models HS2 (long before it was a railway line...) . The larger carb is an H4 or HS4 or HIF38. Fitted to various Minis over the ages and also the source of a larger maniifold - but still with the hot spot... . The Midget twin carbs are a waste of time - no better than a single carb on a GOOD manifold with no 'hot spot'.... The 'MG Metro' inlet manifold (and generic copies) is the one to have - NOT the Turbo version..unless fitting a Turbo....... Are you sure the engine is in good enough condition to take more power? Drive train will be fine - just no racing starts...

[mike.perry]

Don't worry about the whine, start worrying when 1st gear sounds like a bag of spanners.

[bmcecosse]

Some swear by putting a can of STP in the final drive...drain off some oil first.

[ASL642]

Is there any oil in the diff?