Make it fit
the real Midget.

Lucas M35J starter study

The factory Midget 1500 list names 13H5798, the 67H5010 pinion and two mounting bolts. Lucas gives an 88.9 mm yoke outside diameter. The twenty selectable starter groups now include the hollow yoke, four pole shoes, armature and face commutator from Lucas workshop topology, plus the two cataloged mounting bolts, separate inertia-drive pieces and a terminal nut/washer comparison group. The terminal group follows Lucas Fig. 1 item 1 and the exposed hardware in IMG_6969–6970; its count, dimensions and stack order are not verified on the fitted unit. A compatible HC-Cargo 111103 replacement listing provides 125.45 mm hole spacing for the CAD flange; its clocking, full profile, and applicability to the fitted unit remain unverified. A direct measurement from a confirmed fitted M35J can change the two flange-ear and bolt-cue centers in an owner STEP, without establishing the installed orientation or withdrawal clearance. The approximately 150 mm yoke and longer drive are proportioned against that replacement’s published front/rear envelope, not measured from the fitted starter. Internal clearances, winding paths, and installed station remain visual estimates. IMG_6966 and IMG_6969–6970 locate a starter casing below the distributor beside the PF53 filter. Its dark, mostly smooth rear end differs from the ribbed casting pictured for the compatible replacement, so the CAD exterior follows the owner photos there. No readable marking identifies its type, and the drive-end bolt centers remain hidden.

• Photograph the actual starter label, drive end and both fasteners with a scale.
• Measure the mount and withdrawal space before treating the CAD as a replacement guide.

Block, head and crank

IMG_6968 records a stamped block number transcribed by the owner as FP4025UE. The Spridget production register identifies FP as the Midget 1500 engine prefix and UE as the U.S. suffix outside California; UCE denotes California. This classifies the photographed engine number, assuming the worn characters were read correctly. It does not establish the separate chassis identity, original-engine status or which emissions parts remain fitted. The internal bore/stroke/journal data are sourced. The open lower crankcase, three cap stations and separate head gasket follow factory assembly topology, but their modeled sizes are estimates. The head now has an open rocker recess and side reliefs guided by a photographed bare 1500-family head. A straight-on supplier gasket photo, compared with a separate bore-size listing, suggests a roughly 140–150 mm head/deck footprint; the CAD uses a provisional 148 mm head width instead of its former 186 mm. This cross-supplier scale estimate is not a fitment dimension and the fitted casting remains unverified. An Ajusa AJM373-family replacement listing gives a 143 mm width and 365 mm overall length. A near-square-on product image supports roughly 355 mm for the gasket body plus 10 mm for the rear tab and unequal 79.5 / 86.5 / 79.5 mm bore-center intervals. These rounded photo-derived dimensions are used for the separate gasket and related bore geometry. Ten regular openings, tentatively classified as stud passages using the catalog count, now align the block, head, gasket and stud cues; another 21 visible openings are modeled without assigning their function. Exact factory hole coordinates and diameters remain unmeasured. Outer block and head faces, bolt holes, ports, bore pitch and engine mounts remain undimensioned. The engine-mount fitment guide now records the factory CHA280/CHA565 front change point and the rear supports; none has a measured station in this STEP. The four separately selectable spark plugs use Champion N12Y nominal shell dimensions as a period comparison, while the plugs actually fitted and their head axes remain unverified. The parts catalogs identify three large side core plugs and a large/small front pair; all five now have selectable cups and sockets in the CAD. Their nominal diameters follow catalog listings, while centers, depths, walls and access are provisional. The front pair sit behind the separate front engine plate in assembled views. The core-plug guide records the source split and inspection tasks. The separate gasket now includes a photo-derived aperture pattern, and the head/deck envelope is shifted about 15 mm from the bore axis toward the wider passage side seen in supplier photos. The 1500 recessed-bore interface and rear gasket identification tab now appear as study silhouettes, following a Triumph 1500 parts catalog and a Midget 1500 gasket listing. Recess width and depth, tab outline, hole identity, location, orientation, fire-ring design and fitted gasket remain unverified; these shapes cannot guide drilling or gasket selection.

• Confirm all characters of the FP4025UE stamp directly and record casting numbers and the separate chassis plate.
• Measure cylinder-center spacing and head/block length, width, deck height and mounting-face offsets from the actual engine or dimensioned components.
• Make front, side and top square-on image sets with scale targets at the same depth.
• For any head-off repair, record the fitted gasket’s fire rings, coolant/oil holes and fastener pattern before discarding it.

Rocker cover and cap identification

The replacement gasket suggests 360 × 110 mm. IMG_6856 shows a dark cap at the cover opening. IMG_6893 and IMG_6964 show a silver pressure-warning cap over the cover area, apparently set down there; neither establishes it as the oil filler cap. Identify the actual cap and both hold-downs directly. Cover height, exact fastener centers, cap seal and opening still need measurement.

Direct cover body dimensions, hold-down spacing and filler opening can reshape their named features in a separate owner build. They do not establish cap identity, seal fit or cover withdrawal clearance. The breather study now has a connected hollow outlet, supported clamp band and a photo-supported worm-drive housing/head. Direct band width and hex-head across-flats can replace the catalogue comparisons; the housing width follows the selected band as a display choice. Neck size, hose diameter, insertion, clamp clocking and downstream route remain unmeasured. Geometry and STEP checks establish model consistency, not fitted access.

• Measure cover length/width/height and hold-down centers directly.
• Identify the fitted cap and neck first; photograph its underside and measure the seal only when safely removable.
• Photograph the cover square to its top and each side with a ruler.
• During planned breather work, photograph its full route and clamp clocking. Measure band width along the hose axis and head size across opposite flats; record the exposed neck, hose bore and insertion in the project evidence log before adapting their remaining estimates.

Rocker shaft, arms and springs

The factory manual gives a 14.30–14.33 mm rocker-arm bore, four working outer-spring coils and a 34.2 mm fitted outer-spring length. Its printed rocker-shaft inch and metric ranges disagree; the CAD uses a conversion of the inch range and flags the conflict in the data file. The 1500 head parts plate supports eight springs in one lengthwise row, correcting the former two-row model. The external-engine parts plate lists ten head studs, nuts and washers; their modeled stations are approximate. The Midget 1500 head plate also establishes eight guides, eight upper collars, eight lower collars and sixteen split cotters; those groups now appear separately, with corrected stem-to-rocker contact. Replacement valve listings for the Midget/Spitfire 1500 give 108.2 mm overall length and 7.9 mm inlet / 7.8 mm exhaust stem diameters; the CAD now uses those comparison dimensions with factory valve-head diameters. A North American replacement guide listing adds a 52.4 mm length, 12.75 mm outside diameter and 7.97 mm bore; its installed projection and fitted variant on this car remain unknown. Lever contours, guide fits, collar and cotter profiles, spring wire section, valve centers and head-fastener coordinates remain provisional.

• Identify the fitted rocker assembly before ordering a shaft or arms.
• With the cover already removed for service, photograph all eight springs, arm positions and support castings square on.
• Measure an original shaft and the relevant bore directly before a fitment decision; do not rely on the conflicting printed range.

Timing cover and front crank seal

The Midget 1500 catalog separates the front engine plate, timing-cover gasket and oil seal. The provisional oval now follows the crank-to-cam line and clears the modeled chain and sprockets. The photo-scaled housing rear flange and upper passage clear the virtual cover and chain. The revised pump station clears the virtual chain and cover, but its position is inferred from the gasket relationship and model clearance rather than measured on this car. Removal clearance remains unknown. A supplier-listed UKC1110 comparison seal measures 76 × 52 × 10 mm; that scales the virtual ring, cover opening and pulley hub, while a removed-cover photo suggests an approximately 216 × 336 mm oval. These comparison dimensions do not identify the parts on this car. A used 217790U cover photo supports the raised crank-seal collar now in CAD; its taper and projection remain estimates. The Moss Europe 1500 catalogue assigns 14 clockwise A–P cover positions, including two dowels, but the CAD hole centers and fitted hardware remain unverified. The 1500 exploded drawing also places a separate 119390 oil thrower between the crank gear and pulley; the CAD now shows its photographed dish and notch with estimated dimensions. The timing-chain shoe now has the photographed 42425 curve and separate catalogue-listed anchor, rivets and pin hardware; their positions and sizes remain estimates. Plate outline, cover depth, tensioner mount, oil-thrower station and pulley fit remain unmeasured.

• Identify the fitted engine and timing-cover variant before ordering a gasket or seal.
• Photograph the front face square on, then record each fixing, timing mark, pulley and adjacent pump/sump joint.
• During a documented cover repair, measure the real cover and seal bore directly; do not use CAD dimensions as a pattern.

Intake and exhaust manifolds

The 1975–76 parts plate shows separate inlet and exhaust castings, a shared gasket and a downpipe joint. The two new CAD groups show their branching relationship and the carburetor's position closer to the middle of the engine. They do not establish this car's fitted manifold, port centers, stud locations or removal clearance.

• Photograph the full intake and exhaust side from above and below with the engine cold.
• Record casting numbers, hoses, carburetor linkage and downpipe fixing count.
• Measure port and stud centers only from accessible original parts or a gasket that fits this engine.

Metal air cleaner and intake

IMG_6885–6887 identify a separate metal case, elbow and two-clamp rubber joint. The factory air-cleaner plate lists North American 1975 assembly CHA295, a 1976-on change to CHA554, and one GFE1060 element. It does not establish what is fitted to this car. The factory drawing shows a vertical panel between an outboard cover and carb-side backplate. The CAD now follows that order with a provisional 100 × 150 × 280 mm case envelope, separate rounded cover and backplate, two latch studies, and a 30 × 120 × 250 mm panel study. A five-step browser view moves the cover and panel outward; the motion is not a verified removal path. Neither size comes from a factory drawing or direct measurement. The filter seat, sealing face, mount locations and duct diameters remain unknown.

Endpoint identity unresolved: the factory plate distinguishes the gasketed case-to-carburetor flange (148006, two screws and washers) from a separate inlet temperature-control branch (BHH1163 / CHA379 / CHA491 catalog entries). The photographed paired-wire sleeve's remote component is unidentified. The former elbow-to-carburetor description was unsupported; trace the fitted branch before assigning its identity. Catalog entries do not establish which parts remain fitted.

Unresolved intake joint: the current elbow, coupling and carburetor envelopes interfere. The sleeve bore is smaller than the metal outlet envelopes, the metal ends overlap, and fitted end planes remain unmeasured. Two separately selectable paired-wire clamp studies now replace the flat ring cues, following the visible IMG_6885 construction. Their wire dimensions, screw/bridge shape, stations and clocking remain unmeasured display choices. This joint cannot support a reliable disconnection rehearsal. The lid/panel animation has a separate purpose. Trace the remote component; record tube ends, insertion depths, clamp clocking and both outlet axes in a shared measured frame before relocating the joint.

• Measure the fitted case length, width and height, seam and clip positions.
• Open the case, photograph its part markings and measure the removed element and sealing rim before buying a filter.
• Measure both metal tube outside diameters, coupling length and bend centerline offset.

Smiths heater

IMG_6892 confirms SMITHS on the rear casing and shows a round outlet and two hose connections. The CAD's 330 mm width came from a perspective-sensitive comparison and needs replacement with a direct measurement.

• Measure case width, height and depth in place.
• Measure outlet and hose outside diameters, center positions and mounting-hole spacing.
• Record any molded model number and photograph both visible case faces.

Three pairs of main-bearing shells

The Midget 1500 workshop specification, printed 04–1 gives main-bearing length as 21.34–21.72 mm. The CAD now shows each upper and lower half separately at the three crank journals, using the 21.53 mm midpoint. This is a dimensional anchor for the shell length only: the 1.7 mm wall, 0.1 mm radial space, seat shape and journal station are visualization estimates. They cannot determine bearing grade, crush or running clearance.

During a planned bottom-end inspection, record each shell’s station, facing and size marks before removal, then measure the actual journal and housing using the factory procedure. Inspect a lower shell ↗

Crank-pulley retaining nut and shaft reach

Rimmer lists one 155357 nut retaining the Midget 1500 crank pulley, and its photograph shows a hex base with a raised round collar. The previous crank nose ended inside the virtual pulley, leaving no possible retaining interface. The new nose reaches the pulley recess, with a separate nut. A Spitfire 1500 reference reports a 1 13/16-inch socket (46.04 mm across flats); the model hex now follows that reported size, at 53.16 mm across corners. It remains unverified on this car. The 26 mm threaded tip, 17 mm nut height, thread form, recess plane and mating fit are estimates. The model cannot establish tightening torque. Inspect the nut ↗

Crankshaft Woodruff key

Rimmer lists 105115 as one half-round key for the Midget 1500, with a 4.75 mm size. The STEP now separates this key and cuts matching seats in the crank nose, timing sprocket, oil thrower and pulley. Its modeled 19.5 mm length, arc radius, 3 mm projection, angular station and slot clearances are unmeasured. Inspect the actual key and all three mating parts before using this drawing for a repair. Inspect the key ↗

Connecting rods, caps and bearings

The Midget 1500 parts plate lists four rods, eight bolts, a rod-bearing set and four wrist-pin bushes. A fitting H-beam replacement lists a 51.34 mm big-end housing bore, 22.15 mm small-end bore and 22.78/21.6 mm end widths. Those comparison sizes now scale separate rod caps, bearing halves and pin bushes in the CAD. The replacement is not this car’s verified rod. Cap shape, bolt stations, bearing grade, shell thickness and actual journal condition remain unknown.

• At a planned teardown, photograph rod and cap orientation marks before separation.
• Measure each crankpin and actual rod housing before selecting bearings.
• Keep shells and caps indexed by cylinder and upper/lower position for inspection.

Oil filter and electric pump

IMG_6966 identifies the fitted canister as ACDelco PF53. A PF53 product listing gives a 77.0 mm outside diameter, 79.4 mm height, ¾-16 thread and 70.4/62.2 mm gasket diameters. The catalog outside size now scales the CAD canister; it is not a direct measurement of this installed filter. The Midget 1500 external-engine plate separates the filter head, threaded adapter, head-to-block seal and retaining bolt. The fitted adapter thread and sealing seat remain hidden; the photographed PF53 does not establish that a model-year catalog filter will fit. The adjacent electric pump is a separate component whose number, mounting and line routing remain unverified.

The owner builder accepts separate direct straight-shell diameter, rolled-seam diameter and installed height, plus removed-gasket inside/outside diameters. During a planned filter change, direct exposed adapter thread-crest diameter and tip projection from the head seal face can reshape only that exposed portion. The hidden head-side adapter, thread pitch/form, sealing seat, filter internals and extraction path remain unverified. The display socket derives clearance from the selected adapter envelope; its dimensions are not measurements of the removed filter. A recorded obstacle distance remains an access observation, with no proof of rotation or an exit route.

• Record the fitted filter marking and measure its straight shell, rolled seam and mounting-plane-to-end height when accessible.
• During a planned filter change, photograph the removed filter thread, gasket and fitted adapter before selecting a replacement.
• Trace the electric pump inlet, outlet and wiring; record fittings and bracket centers without disconnecting lines.
• Keep straight-shell and rolled-seam diameters separate. Measure adapter projection from the head gasket-sealing face, identify the actual thread, and photograph the removed gasket and baseplate during the planned change.

Water pump and thermostat assembly

The CAD now separates the pump housing, its 138702-style gasket, the pump, thermostat housing and cooling filler position. Supplier gasket photos beside rulers scale the rear 138702 face to about 94 × 61 mm, with three holes and two coolant openings, and the 138701 pump joint to about 91 × 81 mm around a 65 mm opening. The actual fitted parts, mounting stations and depths remain estimates. The 1500 parts listing establishes their relationship. Moss documents a 1975 cooling-system modification affecting the housing, tank and hoses on some cars. IMG_6853 and IMG_6859 show the fitted large thermostat outlet facing the ignition side and a smaller hose on the opposite side. The CAD now follows that orientation with open necks and a separate hose sweep across the visible bend toward the radiator; its final radiator connection, bore, neck sizes and clamp remain unmeasured. The model's case shapes, bolt centers and pulley-to-fan offsets are estimates. The housing now includes a hollow lower-hose spigot and two unthreaded port bosses, following a 144297A replacement-casting photograph. The roughly 34 mm neck diameter and 47 mm projection are oblique-photo estimates; the fitted casting, port threads, sender locations and lower-hose path are unverified. A separate 11K2846-style adaptor, AED172-style washer and short capillary line now mark the temperature-gauge connection suggested by IMG_6895. Moss’s Smiths-gauge instructions specify that capillary arrangement for Midget 1500 cars through 1977, while its cooling catalog lists the later electrical sender from 1978. The actual fitting and line route remain unverified. The virtual pump clears the timing cover, but the relationship between the housing’s head flange and pump seat is still unverified. A trial placement of the three housing-to-head bolts intersected the pump, so the STEP omits them. The Midget 1500 cooling plate, printed pp. 136–137 identifies their 5/16 UNF lengths and positions: upper BH605221 2¾ in, lower-left BH605191 2⅜ in, lower-right BH605181 2¼ in. The drawing is oblique; confirm left and right on the real casting. Measure the face angle and three center-to-center offsets between its two machined faces before relying on the CAD for access or fit.

Direct lower-neck diameter/projection and retaining-bead diameter/axial width can reshape the outlet envelopes in an owner build. Direct upper-neck and bead diameters and both hoses’ relaxed bore/straight outside diameter can replace their corresponding estimates. The hose sockets and supported clamp positions are derived display connections; rubber stretch, compression, sealing and installed access remain unknown. Bead contours and setbacks still need evidence. Housing face angle, center offsets, tapped-port spacing and bolt lengths, plus thermostat gasket/screw readings, remain recorded-only observations. They do not relocate the unresolved joint or prove that its omitted bolts are accessible.

• Record the chassis number and any front-housing casting number.
• With the engine cold, photograph the pump, thermostat outlet, tank and complete hose branches together.
• Measure front-face offsets, pulley alignment and visible mounting centers before planning a replacement.
• During planned cold hose access, measure each straight metal neck separately from its bead. Record lower-bead axial width and any setback, each hose’s relaxed bore and straight outside diameter, actual insertion and clamp station. Keep upper and lower connections distinct.

Fan, pulley and radiator gap

IMG_6895 shows irregular missing material on multiple fan tips. The CAD's 13-blade North American catalog candidate, diameter and mounting spacing do not establish what is fitted; a seven-blade 1500 fan is also listed, but the Rimmer Spitfire plate assigns RKC2126 to a non-viscous mounting, so it is not a proven replacement for the modeled coupling. The finned UKC3532 comparison clutch and four separate fan fixing stacks align with the modeled fan holes, but their dimensions and installed direction remain estimates. A directly counted number of blades can change repetition in a separate owner STEP, but keeps the candidate paddle profile. A directly measured intact fan diameter can resize blade span; an intact blade-tip chord can independently resize the paddle width. One measured adjacent fixing-hole spacing is retained as a comparison note. A separate owner STEP can move the shared fan, clutch and fixing positions only after all four signed X/Y hole centers are measured from the shaft center in a front-facing view. The current public belt loop has about a 989.9 mm outside outline, matching the builder and both public model exports; a viscous-fan CHA328 supplier describes about 1120 mm outside circumference. The fitted belt and groove geometry are unidentified, so the CAD cannot size a replacement. The inspector can separately calculate an approximate outline from three directly recorded shaft-center distances. The geometry does not attempt to reproduce the unknown damage pattern.

• With the engine unable to start, count and photograph every blade and record the molded number.
• Measure maximum shaft-center-to-intact-tip radius, one undamaged blade-tip chord, mounting-hole centers and the fan-tip-to-core-face gap; keep any shroud gap separate.
• Record individual damaged blade positions and replace a damaged fan before any engine run.

Alternator and ignition

IMG_6976 identifies the fitted alternator as a Bosch AL298X remanufactured unit; IMG_6971–6972 show the lower mount and front frame. IMG_6899 shows an ignition coil marked external resistor. The public STEP uses the 108.25 mm outside and 73.95 mm inside diameters from an AL298X-compatible replacement stator catalog, but its surrounding case, mount and engine station remain provisional. The rotor, field winding and slip rings are now separately selectable internal architecture studies following a Bosch cutaway; their fitted dimensions and internal identity are unknown. A Lucas-family interchange note supplies the 15 mm virtual front-shaft comparison, not a measurement of this Bosch reman unit. Its pulley plane, bracket foot and withdrawal clearance cannot authorize a part order. A separate owner STEP can now apply direct measurements of all four case diameters and four axial sections, shaft-to-pivot distance, front and rear ear thicknesses, clear ear gap, pivot-bolt length and observed head side, bracket pivot-lug thickness, and spacer length, bore and outside diameter. The builder checks whether the lug and spacer fill the ear gap and whether the modeled bolt reaches the stack. It can place directly recorded internal washer or shim packs at three axial positions, but their individual piece count, radial sizes and hardware type remain unverified. The rear connector has no verified terminal geometry; the wiring worksheet records what is actually connected before any terminal assignment. The upper adjusting link still has an unresolved overlap with the timing-cover envelope, its virtual slotted arm is 20 mm ahead of the modeled upper-ear face, and its tab hole is about 84 mm away in XY from the photo-traced right/lower housing-gasket hole. That 84 mm is a model discrepancy, not a car measurement or a verified item-16 assignment; Moss Europe cross-lists BH605181 for both link-to-housing and one housing-to-head bolt, so the fitted anchor must be traced. Neither attachment fastener is modeled; the inspector now logs direct axial planes, bend offset and slot dimensions to resolve that mismatch. The factory North American parts list adds CHA304 to the common 147899 bracket and specifies UKC3128/HB841 pivot hardware; those parts are not yet dimensionally reconstructed in the public STEP.

• Photograph the fitted alternator label, rear terminals, both pivot ears, spacer, bracket lug, pulley and full bolt stack from front and rear before disassembly.
• Measure the case sections and the lower mount with a ruler or calipers, recording each datum and photo. Record each washer or shim separately; the owner STEP can place measured axial pack envelopes at three positions, while piece count and radial shapes remain unverified.
• Trace each alternator connection on this car before using any diagram. Check bracket mounting centers and pulley alignment before planning a replacement path.

Body, wheels and chassis

The handbook gives a 2.03 m wheelbase, recorded separately as a body datum. The detailed CAD models the engine. The recovered whole-car reference separately shows body panels, steering, suspension, rear driveline and wheel groups, now with a transmission envelope and four separate brake-corner groups. Published 2032 mm wheelbase and steel-wheel tracks anchor the wheel centers; these are catalog nominal dimensions. Body surfaces, panel gaps, suspension pickups and fitted wheel/tire sizes are not scan verified. No surveyed transform joins this layout to the detailed engine STEP.

• Record chassis plate, wheel/tire markings and ride height.
• Take straight front, rear, side and top views with a visible scale and fixed lens setting.
• For surface fidelity, use calibrated photogrammetry or a direct scan with surveyed control dimensions, then compare key points to the factory measurements.