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Sprite Mk I
Sprite Mk II
(Side Curtains)
Sprite Mk III
(Roll up Windows)
Sprite Mk IV
(fold down top)
Midget Mk I
(Side Curtains)
Midget Mk II
(Roll up Windows)
Midget Mk III
(fold down top)
Midget Mk III RWA
(Round Wheel Arches)
Midget 1500
(Rubber Bumpers)
More images of Midget models here
Index of Sprite / Midget Pages
- Background & Specifications (this page)
- ((Sprite/Midget Maintenance|Maintenance & Repair))
- ((Sprite/Midget Modifications|Modifications))
Table of contents
History
On 20 May, 1958, in Monte Carlo, the Austin Healey Sprite was introduced to the automotive press. The car had been in development for two years. Production commenced at the MG factory in Abington, where approximately 49000 examples were produced through 1961.
The car was designed to be inexpensive to purchase and operate, filling the sales gap for sports cars less expensive than the MGA. In an effort to reduce production costs, many mechanical parts were taken from existing stocks of a several vehicles currently in production. The front suspension came from the Austin A-35. The 948 cc A-series engine was from the Morris Minor but equipped with dual carburettors, increasing power output from 37 to 42.5 hp. The monocoque construction and quarter-elliptical leaf-spring rear suspension was inspired by the Jaguar D-type. Front suspension used coil springs with lower A-arms, and the upper arm was integral with the shock damper. The rack-and-pinion steering, front and rear drum brakes, gearbox, and differential came from the Morris Minor sedan. Further reduction in production expense came from elimination of the trunk lid and discarding the idea of hidden headlights or rotating pods. The headlight pods were simply fixed in the open position, while the trunk lid was considered not only an additional production expense, but weakened the structure. This was, after all, the world's first monocoque production car.
Credit for the car's design was given to Donald Healey, while close sources indicate that the major portion of the design was produced by Gerry Coker and Donald's son Geoffrey Healey. One can not fail to notice the design input of Geoffrey when considering the difference between engine access through the one-piece bonnet assembly of the Sprite as compared to engine access on the Austin Healey 100, designed by Donald Healey himself. In fact Donald Healey later on admitted that he liked the Sprite design better than his own.
Production
Production and specifications.
Sprite |
| Model | Mk I | Mk II | Mk III | Mk IV | ................. |
| Years | 1958 - 1961 | 1961 - 1964 | 1964 - 1966 | 1966 - 1971 | ................. |
| Production | 48987 | 31665 | 25905 | 22790 | ................. |
| Engines | 948 9C | 948 9CG / 1098 10CG | 1098 10CC | 1275 | ................. |
| Power | 34 KW (46 HP) @ 5500 RPM | 37 KW (50 HP) @ 5500.00 RPM / 43 KW (59 HP) @ 5750 RPM | 43 KW (59 HP) @ 5750 RPM | 48 KW (65 HP) @ 6000 RPM | ................. |
| Performance 0-60 MPH | 21 seconds | 20.3 seconds / 18.3 seconds | 18.3 seconds | 14.5 seconds | ................. |
Midget |
| Model | ................. | Mk I | Mk II | Mk III | 1500 |
| Years | ................. | 1961 - 1964 | 1964 - 1966 | 1966 - 1974 | 1974 - 1979 |
| Production | ................. | 25681 | 26601 | 100246 | 73899 |
| Engines | ................. | 948 9CG, 1098 10CG | 1098 10CC | 1275 | 1493 |
| Power | ................. | 37 KW (50 HP) @ 5500.00 RPM / 43 KW (59 HP) @ 5750 RPM | 43 KW (59 HP) @ 5750 RPM | 48 KW (65 HP) @ 6000 RPM | 39 KW (52 HP) @ 5000.00 RPM |
| Performance 0-60 MPH | ................. | 20.3 seconds, 18.3 seconds | 18.3 seconds | 14.5 seconds | 16.0 seconds |
The Mk I Midget came with either the 948 engine and drum brakes or the 1098 engine with disk brakes. There were 16080 examples of the 948 version produced, while 9601 examples of the 1098 version.
The Mk I Midget 1098 engines had 1 3/4 inch main bearings, designated 10CG. With the Mk II Midget, the 1098 engine got 2 inch main bearings designated 10CC.
The Mk III Midget had several variants, most notably the 1966 - 1969 original version, the 1969 - 1971 square wheel arch facelift version, and the 1972 - 1974 round wheel arch. The square wheel arch was re-introduced in late 1974 with the 1500 model.
Acceleration figures are only estimates. The Midget 1500 came with either the 3.9 or 3.7 differential ratios, directly affecting acceleration figures.
Currently identification has been documented very well by authorities at this time. We would like to reprint that documentation here!
Technical Tips
Tuning Bugeye Carbs
The jet nuts should be screwed all the way "up" and then unscrewed two full turns (or "12 flats"). This is the "rough setting" and it assumes that you have the correct needles on the pistons.
Be sure that the pistons move up and down easily. Sometimes the needles are not centered in the jets and they will drag on the jets. You may have to readjust the jets to center them around the piston needles. This should be checked when the jets are screwed all the way up. Lift the piston and let it drop; you should hear a distinct "clunk" when it falls. If not, loosen the large jet-retaining nut at the bottom of the carb, and slowly tighten it while holding the piston down. Lift and drop the piston several times to make sure the jet stays centered as you tighten it. This can be a little tricky, since the jet may move a bit as it's tightened. As the nut starts to get tight, move it only a tiny bit, recheck the centering by lifting and dropping the piston, and then tighten it a tiny bit more. If the needle binds on the jet, loosen the nut a bit, lift and drop the damper until it is free again, and continue the process of tightening the nut. For a good example of how this is done, see http://www.youtube.com/watch?v=sxVFCY_1aSA&feature=related .
This process, to be fair, doesn't always work. Often it happens that the jet seems centered perfectly up to the point of final tightening of the nut. Then, the needle binds again. This occurs because the jet assembly and carburetor body, while machined very precisely, are nevertheless not perfect. Small high spots and depressions in the various pieces tend to find each other, and no matter what you do, the bumps fall into the dents and everything shifts. To avoid this, remove the jet assembly, move the pieces around a bit, and try again. Sometimes just rotating the jet itself 180 degrees is enough.
Next, synchronize the carburetors. With a warm engine, disconnect the throttle linkages so each throttle turns independently. Adjust each idle speed screw separately and listen for a hiss at the air intake (a small hose or even a stethoscope can help). When both are "hissing" about the same, the throttles are pretty even. Lock the throttles back together and set the idle speed for about 700 or 800 RPM. If you are not comfortable synchronizing the carbs "by ear," tools are available to help with the process. One is called a Uni-Syn, which measures the air flow directly. The Uni-Syn is designed for larger carbs than the Bugeye's standard H1, but, with care, it can be made to work. Other synchronizing tools are also available; eBay is a good place to get them.
Be sure to recheck the synchronization after retightening the linkage, and back off the adjuster for the rear carb. Use the front carb adjuster to set the idle speed.
Turn each jet nut up or down the same amount and look for a change in RPM. You want the highest RPM you can get but the engine should not be surging or sounding irregular. If you started with a 750 RPM idle, this may only bring you up to 775....it's not going to be a big difference. I've found that usually this "sweet spot" ends up being about 2 flats "up" (turned in) in most cars but it can vary from car to car.
Now, with air filters off, use a small screwdriver to lift the piston on each carb just a small amount (about 1/16"). If the jet nut is correct, the engine should speed up just a bit and then settle back to the same RPM. If it speeds up and stays, that carb is too rich and you need to turn the jet nut "up" (turn in) to lean it a bit. If the engine slows down, that carb is lean and you need to "drop" the jet nut (turn down) to richen it a little bit.
This is the most difficult part of the process. It requires some experience to get a good feel for it. If you haven't done this before, you might want to try starting a little lean on purpose; an overly lean setting is much easier to see than an overly rich one. Screw in both adjusters 2-3 flats from the 12-flat initial setting, then try lifting each piston 1/16 inch. The idle speed should drop quite noticeably (perhaps even stalling the car), indicating clearly a lean mixture. Screw the jets out a half flat at a time and recheck; you will notice that the drop in engine speed is less pronounced. Keep doing this, and you will reach a point where the speed does not drop and perhaps increases very slightly; that's the right setting. If you continue, you will reach a point where the engine speed increases noticeably and stays there when you lift the piston. At that point, the mixture is clearly too rich, and you've gone too far.
Between each adjustment, tweak the throttle to rev up the engine a little. This allows the piston to move and resettle into the position it will have in normal use.
Be sure to adjust both carbs simultaneously, because they interact somewhat. Don't adjust one to the point where it seems right, then the other; if you do this, the first one may be wrong after you adjust the second. Instead, change one a little, check it, then change the other a little and check that one. Keep going back and forth between the two carbs until the mixture is right.
For more information, see http://www.youtube.com/watch?v=ASeMfXfjNpw&feature=related .
Nial
How to Remove a Bugeye Engine
In a Bugeye, pulling the engine and transmission is a piece of cake. Here is the procedure:
1. As always, observe proper safety precautions, jack stands, wheel chocks, etc.
Raise the car on safe blocks or jack stands. You will need to get under it.
2. Disconnect the battery.
3. Drain the oil from the transmission; if you don't, it will run out the tailshaft when the transmission is tilted.
4. While underneath, remove the clutch slave cylinder and ground strap.
5. Remove the two lower transmission-mount bolts from the bottom of the tunnel.
6. If your car has an exhaust support bracket from the bell housing to the pipe, remove it from the bell housing. Unhook the speedometer cable from the transmission.
7. On a Bugeye, you can remove everything without pulling the bonnet. I prefer to remove it.
8. Drain the cooling system and remove the radiator and hoses. Don't forget the capillary tube for the temperature gauge. Be very careful here. Don't manhandle the tube! Once it is removed, secure it out of the way.
9. Disconnect the hose from the tube to the oil pressure gauge and plug it.
10. Disconnect the wires from the coil to the distributor and from the starter switch to the starter.
11. Remove the alternator, or at least unhook the wires to it.
12. Remove the hoses from the heater valve to the heater and from the heater to the tube at the intake manifold.
13. Disconnect the hose from the supply side of the carburetors and plug the hose.
14. From inside the cockpit, remove the two upper transmission-mount bolts, located on either side of the tunnel, below and forward of the shifter.
15. Remove the shift tower and shifter knob.
Careful: There is a spring loaded anti-rattle plunger that can fall into the extension housing when removing the shift lever. There is a plug on the side of the shifter housing that retains the spring and plunger. Pull that and remove the spring and plunger prior to removing the shifter.
16. Remove the three bolts holding the shifter cover to the top of the rear extension and pull the shifter.
17. Now, back to the engine bay. You can either pull the manifolds from the head and tie them back out of the way, or disconnect the throttle and choke cables and the exhaust pipe. I tie mine out of the way after removing the manifolds.
18. Attach your engine hoist to the engine. I usually uses a bell housing bolt on the upper left corner and a corresponding bolt to the right front corner. Ideally, you will have a tilt mechanism to use in conjunction with the hoist. It makes life much simpler.
19. Put a very small bit of tension on the lift.
20. Disconnect the motor mounts from the front engine plate. Remove the bolts holding the left motor mount to the chassis.
21. Slowly raise the engine. Once it clears the mounts, it will try to swing forward. Continue lifting, making sure it will clear the steering rack, etc. As it comes up, roll the lift away from the car until you're clear.
If the front wheels of your engine lift won't go under the car, remove the cars front wheels and support it with stands under the front rails, near the firewall.
Jeff
Reinstallation Notes
Reinstallation is straightforward; essentially, it simply involves sliding the engine back into the compartment and reconnecting everything. One tricky part, however, is getting the engine onto the mounts and installing the bolts in the transmission mounts. Here is a good way to do it:
1. Attach the diver-side mount to the engine with the mount bracket in the car;
2. Take the passenger mount bracket out of the car and attach the motor mount to it, but don't attach it to the engine yet;
3. Before attending to the engine mounts, loosely install the long lower bolts into the transmission mount through the bottom plate in the car's body. Install the upper bolts similarly from inside the passenger compartment;
4. Drop the driver-side motor mount in its mount bracket and start the nut;
5. Install the passenger mount/bracket assembly;
6. Tighten all bolts and screws in the engine and transmission mounts.
Although it's not necessary to disconnect the drive shaft from the rear end to remove the engine, it is almost impossible to reinstall it this way. By far the easiest way to deal with the drive shaft is to remove it from the differential (only four bolts) and slip it onto the transmission splines when the engine/transmission combination is partly into the car. Thread the drive shaft through the transmission tunnel and reconnect it to the differential flange when the engine and transmission are fully into the car.
Shop manuals insist that you mark the flanges on the drive shaft and differential, before removal, so you can get them back together in the original positions.
How to Change a Spridget Differential
Drain the oil by removing the plug on the bottom of the differential housing.
Remove the wheels, drums and axles in the usual manner.
Remove the four bolts holding the drive shaft to the differential.
Remove the bolt holding the Tee for the hard lines and flex line from the differential. Some don't get rebolted over the years so this may not apply.
Remove the eight nuts securing the differential to the banjo.
Rock the differential to break the sealant; you may need a rubber mallet to help it along.
Clean the mating surface and install a new gasket (I don't use a gasket, just permatex #2 sealant - YMMV).
Install the new differential in the reverse order. Reinstall axles and refill the housing with gear oil. I don't top off the rear-end fluid; I put in just enough so I can touch the level with my pinky.
It isn't a bad job at all; just keep everything clean.
Chris
Replacement and Maintenance Parts
To minimize production costs, Healey designed the Sprite to use a lot of existing BMC parts. This philosophy was carried through the whole production period, at least to some degree, allowing many parts to be used in a wide variety of BMC cars. One of the best ways to find replacement parts is to become aware of these commonalities and to look for listings for an appropriate, but different, car.
Spark Plugs, Wires, and Other Ignition Parts
Accel 3009 wires work fine as non-resistor types. These are available from many sources, including Summit Racing, Advance Auto, and Autozone. Buy a V8 set and get two sets in one. Cut them to the proper length. They are yellow with red cast-in plug caps and are stranded copper wire. Just right for side entrance distributor caps with the screw-in fittings.
Accel 3008 also fits but has straight hoods. In any case, Spridget ignition wire must be 7.0 mm in diameter with a metallic core. This is not a very common size, but not so unusual that it's difficult to find.
NGK BP6ES spark plugs were recommended for 1275 engines by a BCF Spridget-forum consensus in 2008; the hotter version, which should be OK for the stock 948 and 1098, is the BP5ES. The Bugeye shop manual recommends Champion N5 spark plugs; these are obsolete, but type N5C is the modern equivalent. Type N9Y is listed for 1275 engines; the modern number is N9YC.
Ignition parts such as distributor caps, rotors, points, and capacitors are readily available from ordinary parts stores and on-line suppliers. If you have a 948-1275 CC engine and can't find a listing for your car, look for parts for a mid-60s MG Midget. They are all the same, and you're more likely to find a listing for the MG. Earlier cars (through 1968) had a "side entry" cap; later ones, a more conventional "top-entry." Both fit all 948-1275 distributors.
Note that the 1500 engine is a Triumph engine, not a continuation of the BMC AN5 series of engines. It's an entirely different story, so, in general, 1500 parts are not common with any of the earlier engines.
Ignition coils are pretty generic. It's not hard to find listings for these at ordinary auto supply stores or online sales outfits.
Brake Parts
A surprisingly good variety of brake parts are available from conventional auto-parts stores, both local and on-line. It is more likely that the store will have a listing for an MG Midget than a Healey Sprite. If you cannot find a listing for your Sprite, look for a part for an MG Midget of the same year. This is no help for Bugeye Sprite owners, of course, but some knowledge of parts that are common with Bugeyes and later Midgets can be helpful in obtaining what is needed. A lot of the Mk I Midget parts, for example, fit the Mk I (Bugeye) and Mk II Sprites.
For Mk I/II Sprites and Mk I Midgets, from 1958 to 1962, rear drum brakes are different for "early" and "late" cars. Early cars are up to VIN GAN-1-13554 for Midgets, HAN-6-20544 for Sprites. Virtually all rear brake parts are different for early and late cars. The only major exception is rear brake drums, which are the same. If you have an early Sprite, such as a Bugeye, a listing for an early Midget's rear brakes should work, even if it's not the same year. For later Sprites, just use a listing for the same year Midget and you should be safe.
Front drum brakes are identical on all cars that use them; a listing for a 61 or 62 Midget with drums should fit a Bugeye.
Later cars all have disk brakes in front, and these are all the same. Disk-wheel and wire-wheel cars do have different rotors, however.
Brake parts, especially drums and rotors, are regularly available on eBay. This is something of a risky source, as drums and rotors might have been "turned" (shaved down for smoothness) to their limits, and therefore are no longer usable. Exercise some care.
Master cylinders, especially the combined brake/clutch cylinders from earlier cars, are stunningly expensive. If the bores are smooth, these can be rebuilt with an inexpensive rebuilding kit. If the bores have become pitted, a good approach is to have the cylinder resleeved. (See, for example, http://www.brakecylinder.com/ .) This is especially true of the 3/4" master cylinders for early disk-brake cars, which are no longer being made.
Electrical Parts
Many electrical parts are readily available. Many are generic, so you need not find a replacement specifically intended for your car. For example, virtually any 12V starter solenoid will work in a Spridget. The above suggestions regarding an equivalent MG listing apply here as well.
Generators can die because of electrical or bearing failure. Before rushing out to buy a new generator, be sure the generator is definitely bad and irreparable. Often, when a generator fails, all that is needed is a brush replacement and, perhaps, cleaning up the commutator. (See a service manual for details on doing this.) The sintered bronze bearing at the rear of the generator also has a limited lifetime but is easily replaced. Keeping this bearing oiled properly, as indicated in the owner's manual or service manual, will help extend its lifetime. The front bearing in the generator is a standard-size bearing, which is readily available from many sources. It has a long life, however, and won't need replacement very often.
If you have a charging problem, don't automatically assume that it is caused by a generator failure. The voltage regulator, or something as simple as a bad electrical connection, might be the cause. Often, when a regulator fails, simply cleaning the relay contacts will restore it to normal operation. A diamond-surface file, which you can obtain from a well equipped electronics store, is perfect for cleaning the contacts. Electrical terminals on the regulator box are a notorious problem; these must be kept clean, uncorroded, and tight. You can use a later push-terminal regulator to replace the screw-terminal one in the early Sprites; just install the correct terminals onto the wiring. Of course, disconnect the battery before you do any work on the electrical system!
If you have persistent charging problems in a generator-equipped car, it might be worthwhile to replace the generator with a modern alternator. See Alternator Conversions for further information.
Replacement starters are often available on eBay and are not expensive. Often, like generators, they will need minor refurbishment.
Ratings for today's fuses are different from the ones in England when the Spridgets were in production. See Fuses British-US Conversions for more information.
Screws, Bolts, and Nuts
Many of the screws used in British cars are based on older standards, so it may be difficult to find replacements at your local hardware store. Many of the small screws, such at those used in SU carburetors, are based on the BA standard.
Whitworth/BSW bolts, which are common in older cars, had largely fallen out of use by 1960. Although Whitworth fasteners, as such, are not found in Spridgets, occasionally a Whitworth-dimensioned bolt head, nut, or thread may be encountered (e.g., the bolt holding on the float bowl in H1 carburetors). See British and American Bolts and Fasteners in the section on General Technical Articles for more information on those standards.
Bolts based on those older standards can still be obtained from suppliers of specialized bolts. Such suppliers can be found from an ordinary internet search.
Other Parts
Many bearings and seals used in Spridgets, as well as other British cars, are standard sizes. These can be obtained from suppliers other than the usual car-parts sources.
Front Wheel Bearings, all cars
Inner: Timken 07097/07204
Outer: Timken 05066/05185
These must be so-called "face adjusted" bearings. For more information, see this. If you plan to replace front wheel bearings on a Spridget, it's absolutely necessary reading.
Oil Filters
Spin-on filter: AC Delco PF53
Standard fan belt is 900 mm, narrow V-type.
Isuzu Starter
The Isuzu starter will bolt directly to a 1275 without any engine modifications. The Advance Auto Parts number for the starter is 16878. This starter is used on various Isuzu models from 1988 to 1994.
However, it will contact the passenger footwell and a little clearance with a BFH will be required to create a small depression in the footwell. The dent in the vertical wall on the front of the footwell needs to be only about two by two inches and about 3/16 deep to clear the starter. Another thing to take into consideration is the ring gear. The teeth on the ring gear are beveled to accept the drive gear coming from the rear - forward. The Isuzu stater operates from the front to the rear against the bevel on the ring gear.
Frogarri, Anthony
How to Rebuild the Valve Rocker Assembly
This describes a minor rebuild; that is, one in which we do not have to rebush the rocker assembly. First, remove the cotter pin on one side of the assembly; now the stock assemblies are spring-loaded so keep some load on the assembly with your hand until you get a few pieces off. It's a good idea to take every piece off and line it up on the work bench in the same order as it came off the shaft. Besides the order of rocker arms, pedestals and springs, you'll also have shims and end washers on the assembly; keeping them in the order they came off is important. Also, the order of the rocker arms is important. Look closely at A-series rocker arms, especially the base where the shaft passes through. The rocker arms each have one of two offsets; call them lefts and rights if you will. If you jumble up the order of the arms, you'll take a couple hour job and turn it into an all-day job, trying to get everything back in the correct order.
Now, since you're probably rebuilding the engine and everything is new and pretty, it would be a shame to put oil-stained rocker arms and pedestals back on a new shaft. So, every piece being re-used on this assembly should be degreased in solvent, blown dry, bead blasted, and finally cleaned again in solvent. If you have a bead blaster, expect to make many trips back and forth form the work bench, as you need to carry only a piece or two at a time, to keep the order correct.
Once everything is blasted and clean, you can start the reassembly. Remember to clean your new shaft in solvent, as it will be coated with a light grease to keep it from rusting on the shelf. Also, after cleaning it, lube it. I use the same assembly lube as for the motor, CRC Moly Assembly Lube, good stuff and you can get it at NAPA stores. For starters, just assemble all the pieces on the shaft in the same order as when you took them off, including the shims, which should be used in the same places. One of the pedestals will have a set screw in it, and on the shaft there will be a hole for the set screw to go into. This is what locks the shaft down. The shaft stays fixed in position and only the rocker arms pivot. You might think that it would all go back together the way it came apart, and if you're lucky, maybe it will; but most of the time it will not. Anytime a new shaft is introduced to the a assembly, the setscrew hole could be off from one to the next by a little bit. You could blame this on third-world parts I guess, but I've seen the same thing on OEM shafts.
With original shims in their original locations, put the assembly on the head and check where your rocker arms line up on your valve tips. You'd like them to be dead center, but it won't always work out that way; as long as the tip pad on the rocker is completely over the valve tip, you will be good. Also check for side-to-side play on the rocker arm. This is most important for the two end ones, because the rest are spring loaded. You may find that in some places adding an extra shim or even removing a shim helps with alignment or side play. While excessive side play on the two end rockers is something you would like to avoid, you don't want them so tight that rocker does not pivot freely. A little side play is a lot better than being shimmed so tightly that it almost locks the rocker arm. Once you get the alignment and side play as good as it can get, you're done. Expect to take the assembly on and off the head a couple of times to get it all right.
What about bushing rocker arms? You can buy replacement bushings for your rocker arms. This job is too much for most home builders, because you will need to press out the old bushings and press in the new bushings, and on some rocker bushings, redrill oil holes. Then you will have to size the freshly rebushed rocker arms to the new shaft. This can be done a couple of ways, either by reaming the bushings to the correct size or by honing them. I do my rocker-arm bushings on my Sunnen hone, the same machine I use to resize connecting rods. Bottom line for most folks: its lot easier to buy rebushed rocker arms with a new shaft, as they normally come already fitted to the shaft. But don't assume this, be sure to ask before buying. Some vendors will want your old rocker arms as cores.
(From Hap Waldrop, slightly edited.)
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