Midget engine - straight swap?

[sowden]

Hi all,

Can anyone tell me:

would this

http://cgi.ebay.co.uk/MG-Midget-1275-En ... 240%3A1318

fit straight into a minor as is, please?

Cheers

Russ

[PSL184]

Yes, should drop in OK but you'll have to find starter, dizzy etc that appears to be missing....

[sowden]

Thanks PSL. Will these missing bits swap straight over from a 1098 engine, do you know?

[PSL184]

Not sure about starter motor. I used a 1098 starter but I was also using a 1098 backplate - I don't know if the mounting holes are in the same place on a midget? Dizzy - No. Both manifolds would fit but they are not ideal. Carb would be too small.... Alternator or dynamo - YES !!

[Matt]

Starter will fit.

1275 midget engines had twin 1.25" carbs from the factory. However I would suggest using a HIF44 and an alloy type inlet manifold. An iron one from a metro is similar but you will need to cut the exhaust section off

[bmcecosse]

It will fit as a complete unit - BUT, the Spridget has hydraulic clutch actuation - and the Minor is mechanical. The Spridget clutch is also smaller diameter and stiffer springs. So - you would need to convert the car to hydraulic actuation - OR change the Spridget clutch etc for the Minor items - which may mean modifying the Minor flywheel to fit on the tail of the crank. That's the way i would go! Dizzy is 25D type - so yes a Minor dizzy will fit - but won't be ideal advance curve - and as Matt says - better to source and use a decent single carb and manifold, and a decent exhaust manifold and system. The Spridget exhaust manifold etc won't fit in a Minor. And yes a Minor starter will fit - although there has been some talk of the bendix fouling the flywheel slightly (although I think that may be with Marina/Ital swaps - Spridget should be fine) - so that would need checking out!

[PSL184]

BMC correctly states the Spridget exhaust manifold and exhaust system won't fit, but the question was will a 1098 manifold fit - which it will but won't be ideal....

[bmcecosse]

Yes indeed - the 1098 manifolds etc will fit and the engine will run - but it will be 'strangled'! The only problem area is the clutch.

[IslipMinor]

Straight swap. Front mounts are the same, use the Minor rear gearbox mount, including the steady cable. Minor starter OK, distributor needs to be Midget spec (Minor gives too much mechanical advance), manifolds as suggested, HIF44 on a decent manifold (MG Metro is an example) and a bigger exhaust than a standard Minor. The standard Minor carb is much too small and would not allow the engine to run properly at all. The exhaust is the only real expense as it should be an LCB, and secondhand they are not very common.

The steady bar to the bulkhead will need to be turned upside down as the block is taller - it will also need a small amount of filing to miss the heater tap, which is at an angle on the 1275 engine. Top hose to the radiator will either need to have an elbow, or, for the 'original' look, get a thermostat housing from a 'B-series' engine and open up the 3 holes to 3/8" and it fits perfectly! All other hoses use standard Minor.

Although smaller than a 1098, the Midget 1275 has a diaphragm clutch and is very easy to use. The 1275 clutch is no problem, just swap the release arm for a standard Minor one and connect to the standard Minor mechanical release mechanism. That's what I have, albeit with a special driven plate for the Toyota gearbox.

Some thicker oil in the dampers all round, front anti-roll bar and uprated front brakes will make a good fun car. Maybe a touch of lowering to improve the handling?

[mike.perry]

You can use the Midget clutch without converting to hydraulics.
Take the Minor clutch relay shaft and weld 1 in onto the arm that attaches to the clutch pedal and re drill the hole. This will increase the movement on the clutch pedal and reduce the pedal pressure required so that it feels like a standard 1098 clutch. Also use the 1098 clutch forks and for good measure you can use a roller bearing clutch release bearing. I have the setup on my 1275 traveller and it works perfectly.

A couple of other alterations:- The heater tap angle is at 45 deg to the cylinder head on the Midget head so the Minor heater tap may foul the battery. You may have to swap it for the Midget unit.
The base of the tap will interfere with the stabilizer bracket so you will have to cut a V out of the bracket.

You can buy a 1275 / 1098 conversion thermostat housing from Birmingham MMC.

You will need to fit some thick washers between the fan blades and the water pump pulley to clear the breather trap on the timing case. These washers will need flats cut on one side to clear the water pump shaft.

The 1275 engine operates on a negative crankcase pressure breathing system, that is the pressure has to be sucked out of the engine via a breather pipe from the breather trap to the carb or to a breather control valve on the inlet manifold. Failure to do this will result in excessive oil leaks from the rear of the engine

If you are using the gearbox as well this is externally identical to the 1098 box with closer ratio gears and automatic reversing light switch.

[rayofleamington]

The standard Minor carb is much too small and would not allow the engine to run properly at all.

that's what I thought until I tried it - top speed is limited by the standard diff, but torque up hills was great (basically it didn't get slowed by some serious hills). The smaller carb will limit top revs but gives better torque.

[sowden]

sorry, just re-reading the post before this one, and wondered whether 2 x 1.25" carbs would preserve the torque but not stunt top top end Revs?

Cheers,

R

[mike.perry]

I have twin 1 1/4 carbs on my Traveller and I would say that unless you are a devotee of the classic twin carb setup then I wouldn't bother. They are probably more trouble than they are worth and I have yet to detect any real performance benefit. I would say that for instant gratification you would be better off with an HIF 44 on a decent inlet manifold.

[sowden]

not an HIF38, Mike?

[PSL184]

If its not a massively modified/tuned engine the HIF38 will be fine...

[mike.perry]

No personal experience of HIF carbs, just a guess, 38 being equivalent to an HS4 1 1/2in, 44 = HS6 1 3/4in. Maybe an HIF44 is too big for a 1275? Would it lack mid range torque?

[bmcecosse]

HIF 44 is ideal for a 1275! An HIF 38 can be used of course - but it will run out of steam at high revs. The whole beauty of the SU carb is that the choke area is variable - and so at low/medium revs the piston only opens as far as necessary - and so the conditions are ideal across a wide rev range. This of course assumes the carb is set up correctly for the intended use - and different springs can be fitted above the piston to regulate how much it opens for given air flow - and different oils can be used in the damper to regulate how quickly the piston lifts when the throttle is suddenly opened. The main advantage of the HIF over earlier SUs is the float arrangement which allows it to be used over a range of mounting angles - and pretty much eliminates any surging or spluttering when cornering !