The fitted
Zenith-Stromberg.

Compare the car with the drawing

Tap a part in the model

Explore the assembly, one layer at a time

Open the interactive carburetor study and use Start study beneath the part details or the controls over the model. Seven views separate the cap with its damper-rod reference, visible screw group, cover, air-valve spring study, diaphragm, air valve and bowl. The order follows the factory exploded drawing as a visual explanation; it does not establish a safe removal path, full fastener count or service dimensions for this fitted unit.

Follow the damper below the yellow cap

IMG_6958 shows the yellow cap, but not the parts underneath it. The British Leyland S1040 typical CD4 drawing, PDF p. 26 / printed p. 23, shows the cap-carried damper rod and hydraulic valve entering the air-valve guide. Its operating explanation, PDF p. 8, distinguishes hydraulic damping of the air valve from fuel metering by the needle below it. This reference does not identify this car’s fitted carburetor or calibration.

The damper rod and valve are now a separate selectable reference. The yellow cap keeps its existing measurement meaning and geometry; the two move together in the assembly study and exploded view. The cover neck has a plain display opening and the air-valve guide has a blind reference cavity. The offset casting boss is lower than the cap head in the owner photo; its revised height is still a visual estimate. Threads, seal, retention and one-way valve details remain unmodeled.

All hidden rod, valve and bore dimensions are estimates. The modeled gaps are not running clearances, oil specifications, damping calibration or a verified extraction path. Outside cover/cap measurements cannot establish those hidden fits. A rebuilt owner model reports overlaps rather than changing a direct outside reading to make the parts fit; older exports without the damper record must be rebuilt before this relationship applies.

During planned service of an identified carburetor, photograph the actual cap-carried assembly and record its marking, rod length/diameter, valve form/diameter, attachment and guide bore with named datums. Keep it distinct from the calibrated metering needle and preserve the applicable service instructions.

Keep the calibrated needle distinct

The factory CD4 drawing separates the metering needle from the piston. The S1040 reference, PDF p. 33 / printed p. 30, describes the air valve, diaphragm and needle as a group before needle-specific work. That reference does not identify the fitted carburetor or justify changing its calibration.

The needle is now separately selectable in CAD, and stays with the air valve during the assembly study. Its old cone and station are preserved: it is a recognition cue, not a measured stepped profile. A 1 mm estimated gap to the piston remains an unresolved holder connection; it is not a shoulder setting on your car. The holder, fixing screw and jet passage are unmodeled.

A needle marking alone does not identify its attachment. The Midget catalog, item 5 lists a fixed 44A needle (374-405) for C3754/C3755, but a different, adjustable 44A (374-415) for C3838. It groups the adjusting screw, O-ring and retaining clip under adjustable needles. Read the fitted carburetor tag and inspect its actual carrier before assigning that hardware to this car; a 44A marking or the engine year cannot settle the attachment. The virtual needle remains a generic recognition cone with an unresolved holder connection.

During planned service of an identified carburetor, record the actual needle marking, carrier/fixing arrangement and shoulder position with a scale and source photo. Retain its matching piston and holder. Needle calibration needs the applicable specification or measured profile stations; overall length, a cone shape or vehicle year cannot select a replacement or fuel curve.

The air-valve spring is a reference study

The British Leyland S1040 CD4 exploded drawing, PDF p. 26 / printed p. 23, places a spring beneath the dashpot cover around the piston guide. The CAD now includes that previously missing relationship as a separate selectable spring study. This is the internal air-valve spring, distinct from the external controls below. The five displayed turns, wire size, diameter, length and ends are unmeasured display choices. They do not identify this car's spring, its free or installed length, preload or calibration.

The assembly view separates the spring without changing its length. It does not simulate force or a service release motion. During planned service of an identified carburetor, preserve the actual spring and record its marking or color, free length, outside diameter, wire size, coil count and end treatment. Keep installed and loose-part measurements distinct.

Make the cover match your car

The CAD now has named fields for the widest round dome diameter, the flange outside width and length, and the yellow cap maximum diameter. Use the cover inspector and cap inspector: open Measurements and model details, choose directly measured on this car, record where the ruler or caliper touched, then export the measurement log. A separate owner STEP build can resize those outside shapes. The public CAD and hidden screw threads, internal clearances and removal path do not become verified through this measurement.

IMG_6958 has no ruler beside the cover. To record a photo estimate, take a new square-on photo with a ruler at the same depth; the photo worksheet keeps estimates separate from direct measurements.

Compare the pale hex and central screw

Below the cover in IMG_6958, a pale hexagonal surround carries a central slotted metal screw. The S1040 CD4 right-side drawing, PDF p. 19 / printed p. 16, shows a comparable pair labeled coarse-idle and fine-idle adjustment. The CD4 exploded drawing, PDF p. 26, separates the outer coarse adjuster and inner fine screw above an emulsion slow-run housing. This supports an idle-regulator candidate for the photographed feature; it does not confirm the fitted tag, exact assembly, hidden passages or calibration.

The idle/slow-run circuit explanation, PDF p. 10 / printed p. 7, describes this circuit on some CD4 applications and notes that mixture still passes via the metering needle. It is not a universal adjustment instruction. The CD4T 150 side diagram, PDF p. 21, shows main-mixture adjustment accessed through the top, separately from the hydraulic damper. Neither diagram proves that this car retains that adjustable-needle arrangement. Keep the pale side control, yellow damper cap and calibrated fuel needle distinct.

The nearby hose and clamp are also visible. Their position beside the candidate adjuster does not establish their purpose. Although the reference drawing labels a crankcase/charcoal-canister purge pipe in this area, the photographed hose must be traced to its actual endpoints before assigning a fuel, vacuum, purge or coolant role. No port route or connection to the idle circuit is inferred here.

1. Photograph this side and the opposite side of the fitted carburetor, including its attached tag, the pale outer hex, central screw and the casting beneath them.
2. Record the controls as found. Identify the exact carburetor and applicable service instructions before changing either control; the photo comparison supplies no setting or number of turns.
3. Trace the adjacent hose by sight to both endpoints and record each port, intermediate fitting and connection. Keep an obscured endpoint unknown. In a hose-inspection project, use the Connections tab to keep the two endpoints, configuration, trace coverage and photo references together.
4. During appropriate planned access, record the outside fitting dimensions and mounting faces with a scale at the same plane. Its thread, internal seat, passage and adjustment range need separate evidence.

This candidate and its hose joint remain unmodeled. The existing generic body bosses do not represent an identified idle regulator, and the current CAD cannot establish tool access or a replacement path around it.

Compare the primary flange

Select the carburetor or cleaner backplate in CAD, then choose Compare cleaner and carburetor flange. The static view shows both sides of the modeled connection and the manifold. Its reported gap is a reconstruction discrepancy; the actual gasket, fixings, flange faces and installed angle still need a shared survey. The separately clamped temperature-control inlet branch is outside this flange comparison. The round vacuum unit visible in IMG_6887 is also unmodeled; identify it and survey its shape and attachments before relying on the model for access around the fitted carburetor.

Keep the fitted tag reading separate

The reviewed IMG_6839 and IMG_6958 views show the maker's casting name but no readable fitted tag number. The worn tune decal in IMG_6957 is separate vehicle-setting evidence; it cannot identify a replacement carburetor or fill missing tag characters.

In the carburetor body inspector, open Measurements and model details. Record whether the actual tag is not located, located but unreadable, partly readable or fully readable. Enter only visible characters, preserving punctuation and case; use ? for uncertainty and keep that reading partial. Name the attachment or stamping surface and photo reference. A loose tag, cover casting legend, engine stamp or catalog application is not an attached carburetor tag.

Choose the source method and retain the observation in the exported browser log. Direct observations with a source note also remain in an owner build's evidence report when that log contains a supported direct dimension. Identity observations alone do not generate a geometry build. A saved complete transcription is still an owner observation, not automatic catalog validation: neither C3754 nor C3755 selects a variant, rebuild kit, spring, needle, port routing or adjustment procedure in the CAD.

Cover heads: visible evidence and catalog count

IMG_6839 shows at least three cross-recess perimeter heads: at the upper left, lower left and right edge of the photographed cover. The fourth side is not fully exposed. Locate those three visible heads ↗. The cross shape alone does not establish Phillips, Pozidriv, a driver size or the original screw specification.

The Midget 1500 catalog, PDF p.42 / printed p.24, item 4 lists four cover-to-body screws, 365-380. The current CAD replaces its former two slotted markers with four separate head cues in the existing group. Count comes from the catalog; cross-recess appearance comes from the owner photo. The estimated four-corner positions are not mapped one-to-one onto the photographed heads.

The head-only references omit shanks, holes and threads. In the public source, the estimated heads intersect the estimated cover shoulder; its native export records that reconstruction conflict without cutting invented seats or moving the measured outside cover dimensions. It is not evidence of interference on the car. During planned access, photograph the complete flange and keep each actual screw identified by its real hole. Record head style and drive, any washer, under-head length, thread and center positions before selecting replacements. The animation does not establish release distance, tool access or tightening.

Map the external throttle and choke controls

IMG_6839 shows an external coiled spring, a threaded adjuster with an exposed wire, and metal linkage below the cover. The crossing hose and viewing angle hide important attachments. These observations do not establish the complete routes, the cable’s role, spring count or fitted linkage variant. The CAD throttle disc and spindle are internal references; the external cables, brackets, levers, links, spring anchors and retention are absent. The separate spring beneath the dashpot cover acts on the air valve and cannot stand in for an external throttle-return spring.

The factory MD0397 plate, PDF p. 124, printed 107-D50·05/06 separates two arrangements. Its first group is marked Federal through 1977; the other is marked California and Federal from 1977. Those labels do not select this car’s fitted hardware, particularly at the overlapping year. Inspect the actual bracket, links, pivots, cable seats and anchors, including any changed or additional parts.

Record the as-found connections

1. Give each observed component and connection a stable owner label tied to physical landmarks and photos. Record the actual carburetor tag and linkage marks, including unreadable or partial marks. Use the worksheet’s observation lists without forcing the catalog quantities.
2. Trace each control independently. Record both outer-cable seats/clamps and the inner wire’s actual end attachments; keep throttle and choke roles unknown until traced. Document the adjuster and retention as found without changing their settings to match the drawing.
3. For each actual spring, record both hooks and their individual anchors. A hose-hidden section of one spring is not evidence of a second spring. A threaded adjuster or coiled cable covering is not automatically another return spring. Keep installed hook-to-hook datums separate from a removed spring’s free-length datums; remove nothing solely to measure it.
4. Record link ends, pivot pins, clips, washers and their order during already-planned access. Preserve a wider view showing which casting or bracket carries each connection. Note the first visible obstruction without treating visibility as tool clearance or a removal path.
5. Keep photo observations separate from direct readings and retain the configuration and source of each. Spatial CAD placement still requires a shared physical-frame survey; this connection worksheet does not supply coordinates, operating travel, preload, force or adjustment values.

The blank record is an evidence worksheet, not a CAD measurement-log import. It does not choose a replacement linkage, prescribe adjustment, move controls or establish a safe disconnection sequence. Use the applicable instructions after identifying the fitted arrangement. The marked photo remains useful alongside older imported models because it records a visible area, not evidence that their hidden internals or omitted attachments are fitted correctly.

Before a carburetor project

1. Photograph the brass identification tag or stamped number close-up and include a wider image that shows where it sits on the fitted unit.
2. Photograph both sides, the throttle and choke linkages, all fuel and vacuum hose connections, and the air-cleaner coupling before disconnecting anything.
3. Measure the outside dome diameter, cover height and screw centers directly if an overhaul is planned. Record measurements with the corresponding photograph; the CAD's outside dimensions are provisional.
4. Match the exact identified carburetor to the appropriate factory procedure and kit. The factory CD4T 150 side diagram, PDF p. 21 and CD4 exploded view, PDF p. 26 help identify parts but do not prove this car's exact variant.
5. If dismantling is actually needed, document cover screw positions, diaphragm orientation, piston, spring, needle, float and gasket as removed. Keep small calibrated parts labeled and clean; use the full applicable instructions for service and reassembly.

Additional installed view · IMG_7036

This view adds context around the installed carburetor and its neighbors. It does not make a tag or casting number readable, identify the lower hexagonal features, establish their threads or function, or expose a complete mounting/hose connection. No fitted dimension, additional CAD feature or verified removal path is inferred from the blurred regions. The sharper existing views retain their role as the primary detail evidence.

New owner evidence · IMG_7034–7042

These views are integrated as direct visual evidence. They do not establish hidden thread or seal geometry, calibrated mounting coordinates, electrical compatibility or a verified removal path. Browse all nine new photographs ↗