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The IDY BIDI Tech Specs (in progress)
(S) written for a Sprite but may work on Minis as well
(M) written for a Mini but may work on a sprite as well
Overflow tanks explained (All)
Gas Tank switch and Autometer tank sender (M)
Subject: Alternator conversion, full details (Sprite)
From: Terry Isherwood
These details only apply to a 1972 1275 UK spec model. You may be able to do similar to others but you need to check first. I did not destroy any of
the original equipment so I can always revert to as built condition. Later 1275 midgets 1973/4 had alternators as
standard. I suggest you read it all first and make sure you understand it. Perhaps even take off your regulator
box and identify what you will have to do. Well I did say FULL instructions, didn't I. Sorry!
Checks to do first
The regulator box is a Lucas 340, mounted on the drivers side of the bulkhead.
Electrical connections to the regulator box are by two moulded push on connector blocks.
At the starter solenoid where the lead from the battery bolt on there is a connector plate with one spare tag. If not you will need one**
Tools
Large soldering iron.
Dremmel or similar tool with cutting disc.
Shopping list
One Lucas 16ACR alternator (34 amp, better than a 22amp dynamo), but I think you could use the higher rated 17ACR or 18ACR.
not that there is a lot of electrics on a midget, but if you have 24 spotlights you might need
one!
One new alternator rear mounting bracket. The alternator is shorter than the dynamo. If you get the alternator from a spridget breakers they can
supply one of these. I got mine from Classic Cars of Kent and the alternator was complete with fixing bolts but these seemed the same as
used by the dynamo.
One burnt out regulator box Lucas340 to cannibalise
One new fan belt. The alternator has a bigger pulley then the dynamo so you need a longer fan belt. Suggest buying the one for a 1275 midget with
alternator. The original one only just goes on at minimum adjustment and even then it is a bit tight.
One 35 amp Lucas female spade connector *
One 15 amp Lucas female spade connector *
Two foot 15 amp wire. Should be brown *
* I got these from Halfords but any auto bits store should have them
One foot of 1mm (40 thou) thick copper or brass strip 5mm or 1/4 inch wide to link the terminals of the regulator box.. Model shops often have a
display stand of such material.
** One ring tag to go under terminal carrying battery wire.
Mechanical
Disconnect battery. Slacken fan belt adjustment bolt/nut. Remove dynamo, two long bolts at top and one small one securing the
adjustment bracket at bottom. Remove rear mounting bracket, two bolts into engine block. Fit
new rear bracket (loosely, it is slotted to take up tolerances), alternator and new fan belt. Adjust up and tighten all bolts doing the rear
mounting bracket last so it fits in the right position without straining the alternator.
Electrical (Now for the difficult bit.)
The alternator has three connections, two large, 35 amp spades, and one small. They are large (sense), large (output), small (ignition lamp) in
that order. The large lead that went to the dynamo goes to the centre terminal of the alternator, a large spade. This is the output. The small
lead that went to the dynamo goes to the small terminal of the alternator.This is for the ignition light.
Make up a lead of brown wire with the 35 amp female connector at one end and the 15 amp female at the other. It goes from the one remaining large spade
connector on the alternator to the spare tag** on the starter solenoid where the battery lead goes. This is the sense wire and the alternator uses this
to keep the battery volts constant irrespective of the current being taken by the lights etc which causes a volt drop in the wiring.
Modify a burnt out regulator box as follows. We need to totally disconnect the box terminals from the guts inside and add two copper strips across them
to reconnect them in a different way . This will enable you to simply plug the connector
blocks into the regulator and achieve the correct wiring for the alternator. We are only using the connectors of the box as a convenient way of changing
the wiring, not any of the bits inside it. I have looked at several 340 boxes. Later ones have copper connectors, earlier ones tinned steel. If
possible get a copper one as it will be easier to solder to. Early boxes have the lid held on with two screws later ones use a plastic peg, just push
it out. It is important to make good soldered connections. If the steel type, and mine was and it was a bit rusty, make sure you clean back to bare
metal and use an active flux to pre tin before soldering on the new strip. I used a small grindstone in my little dremmel drill. Clean the joints
after to prevent more corrosion. The copper/brass strips go between the tag fixing rivets and where the connectors slide on.
But first there are some important difference between the two types of boxes which affect us, the easier one of the two to modify will be the later,
copper type. To isolate the tags from the guts I used a small slitting disc in my dremmel drill making the cut just behind the rivets that hold the tags
on. The tags are
Two large ones marked B (battery). Disconnect them from the guts. On the earlier box there is a spur on the back of the tags which goes up into the
box, on the later there is a link inside. Cut through the spur or the link.
One small tag marked F (field). Disconnect it from the guts.
One small tag marked WL (warning light). This tag is not in line with the others. It is connected to the D tag on the box. It has to be separated
and joined to the F tag. On the copper 340 the WL tag has its own securing rivet so you can slit through the link. On the earlier box the rivets that
held on the D tag also held on the WL tab so if you slit the link first it will fall off. Cut a bit of your copper/brass strip, bend it to shape, and use
it to link the F and WL tags, soldering it securely. Now you can slit the link
One large tag marked D (dynamo). Disconnect it from the guts. It has to be joined to the B tags. Again use a bit of your copper/brass strip, bend it
to shape, and use it to link the D and B tags, soldering it securely. I bent mine up so it passed over the other link and down again. Remember the
box is fitted on distant spacers and has resistors on the back. Do not exceed the height of the resistors and your links will not short out on the
bulkhead.
One small earth tag, forget it we don't need it.
Screw modified box back. Refit connector blocks. Now to check it out. Make sure all electrics are off. I momentary touched the battery terminal
to the battery and watched for sparks or smoke, none so OK. I then put on the interior light and again I momentary touched the battery terminal to
the battery and made sure the light lit up, OK again so the link from D to B on our modified box is OK. Then ignition on and again. I momentary touched
the battery terminal to the battery and made sure the ignition warning light lit up, it did so our link from F to WL on the modified box is OK.
Now permanent battery connection and start her up. Ignition warning lamp goes out, it does, so OK. If you have a volt meter (borrow one if you have
not) measure the battery volts, should be 14v. If it is our new sense wire is working. Put on headlights and at tick over battery volts drop to 12.5
(ish) rev up engine and volts climb back to 14 (ish).
I think that's it. Congratulate your self.
Terry
Subject: Placement of an electric fuel (Sprite)
From: HyperSprite
Placement of an electric fuel pump is important. Most electric pumps are pushers (push fuel to the carburetor) while most mechanical pumps are pullers (pull from the tank). It is best to mount an electric pump near the fuel pump as low as possible. On my car it is mounted where the axel tunnel starts near the fuel tank. In this configuration the draw is only 12 inches in a cool location, so vaporization before the pump is unlikely and any vapor in the line after the pump will be pushed into the float bowl and expelled through the carburetor vent.
Chris D.
From: HyperSprite
Assuming all the parts are good and you are using the big impeller water pump.
1) Are you running a fan shroud and the radiator to body seal? If not you may be re-circulating hot air or not pushing enough through the radiator at idle. Without the shroud on the fan side it is easier for the air to deflect off the radiator than go through it. Without the body seal it can just come back around and into the fan again.
2) Check for a lean idle
3) Check for to much retard in the timing, if you have taken off the vacuum advance (that only comes on a high vacuum e.g. idle and slow cruse) you will need to compensate with more static advance and less total.
4) Add an overflow tank (catch can with the overflow hose submerged in fluid at all times). If the car boils over after it is parked the excess water is pushed into the can, as the water cools it is drawn back into the radiator. Air in the radiator will lower the boiling temperature of the water and cause more boil over and the more water you loose the faster it will boil.
5) If worse comes to worse you can do what I did to my racer.
Take the heater takeoff that comes from #4 (run it through the heater if you like) and connect it to the top radiator hose (I use a lower hose from a sprite cut to fit and a piece of copper tubing). Then plug the lower hose take off. The down side to this, your car will take longer to warm up in the cold months because you are not re-circulating hot water back into the block.
6) Add an electric puller fan under the fender.
Hope this helps
Chris
Overflow tanks explained (All)
From: HyperSprite
An overflow tank allows for water expansion and return but the water is not stored under pressure in the tank and air is never allowed in the cooling system. This permits your radiator cap to govern the boiling point instead of the amount of air in the system. An overflow tank uses a standard radiator cap with the tiny check valve in the center to allow water back in when the car cools and a bottle with your overflow hose submerged in about a pint of coolant (see diagram). The tank should be mounted below the radiator cap level. I have used window washer bottles in the past but now prefer jaz tanks, whatever tank you use it must have a vent to the outside or the cap will come off. You can also buy kits for this at most auto part stores but the bottles tend to be to big to mount under the mini hood.How do you know you have a proper radiator cap? Most do because even without the over flow tank they have to allow air back in when the water cools after it has boiled out. Take the cap off, turn it upside down. You will see a large rubber gasket and then a small (little smaller than a dime) brass button. It is spring loaded to close against the rubber gasket. You should be able to gently pull it up from its seat about an 1/8 of an inch. That is the water return valve.
This system relies on an air tight fit for the hose and cap (old caps should be discarded). If there are any leaks here, air will be sucked back in to the radiator and all the hard work is worthless.
From: HyperSprite
1 wire for slow speed (will not have this on one speed
wipers)
1 wire for a regular speed (you can call it fast if you
like but that is a matter of opinion)
1 wire for momentary (for washer action or single wipe and
back to park, something like that)
1 wire for power (constant with ignition on is for wiper
park, done by a little micro switch inside the wheel housing of the wiper motor,
allowing your wipers will continue to run until they are back down in the parked
position.)
1 wire for ground (on most this wire comes off
the motor and to one of the bolts securing the motor, but it’s a little fuzzy
right now)
From: HyperSprite
Keeping the back 1/4 windows open on a Mini has never been easy. Some of the remedies I have seen include plastic spoon handles cut to fit, stuffed animals, and tennis balls. None of these are all that elegant and none allow closing the window without getting out of the car. Here is my solution to the problem, simple, cheep, and easy.
Start with a piece of 1/2" OD rubber (or other soft) tubing and
cut it to 5/8" long.
Put a nylon tie through the hose and with the window open, wrap the tie around
the pivot connecting to the window.
Hold the hose as you tighten so it is positioned facing inside the car (see
picture) and pull the tie snug.
get inside the car, close the window and pull it tight, not hercules tight, just
tight.
Snip off the excess tie.
Try opening your window. You will notice the tube puts pressure on the window
when it is open, but operation is not hindered.
This picture is from the bottom side because I
had a easier time getting the camera in there.
