Below the
manifold.
A hollow downpipe, inlet flange, three fixing envelopes and a separate flange/olive coupling reference extend from the maintained native manifold gasket. They retain the source engine’s metric scale and estimated whole-car pose.
The old independent underfloor endpoint is replaced by a hollow cross-car main pipe. Factory plate 127 and the MGOC replacement-system note support the opposite-side manifold relationship. The reference starts at the revised coupling rear face; its height lowers from body Y=.23 to .12 (93.13 mm) to place the comparison below the estimated gearbox. The manifold flange and engine/body positions are retained. This construction correction does not establish fitted bends, clearance, sealing or actual catalyst configuration.
Inspect the joint boundaries
Reconciled evidence
Owner IMG_7042 shows the lower manifold flange and descending pipe neck, beside the rust-colored casting, round housing and rigid union. Hidden contours, a calibrated flange survey and the complete underfloor route are not supplied by that view. Existing IMG_6887/6839 manifold evidence remains relevant. These observations do not identify a catalyst or ordinary fitted downpipe.
Factory 1500 exhaust plate 127 distinguishes GEX1618 downpipe, except California, from CHA287 catalyst/downpipe for California. It separately lists GEG742 gasket, coupling olive and fixing hardware. This geometry studies the ordinary topology only; it is not a selection of the fitted configuration. The California assembly remains unmodeled.
Dimensions and construction choices
| Boundary | Basis and limits |
|---|---|
| Source gasket / new flange | The inlet reuses the maintained GEG742 comparison: supplier 52 mm opening and one 70 mm stud pitch. The equilateral three-hole pattern, outer contour, 9 mm holes, 6 mm flange thickness and installed clocking remain estimates. The new flange face meets the source gasket’s lower face; this does not establish actual bearing coverage, compression or a sealed joint. |
| Downpipe | A planar vertical neck, tangent 90 mm-radius bend and rearward run provide an ordinary-pipe reference. The neck has estimated 29/26 mm outer/inner radii. A separate reducer transitions to the underfloor reference’s illustrative outside radius. Its station and 3 mm downstream wall are estimates. No pipe-cutting or bending template is supplied. |
| Coupling | Two annular flange envelopes, an olive ring and three fastener envelopes represent the factory joint architecture. Flange diameter, 60 mm fixing PCD, holes, sections, thicknesses, gasket/olive contact and fastener shape are estimates. Catalog hardware quantity does not establish the fitted pattern or thread. |
| Declared station correction | The earlier 514.07 mm lateral mismatch describes superseded drawing endpoints. The main reference now starts at the coupling rear face, after its estimated center lowers 93.13 mm. Front neck/bend and coupling poses change; inlet flange, manifold fixings and source engine/body positions are retained. All dimensions remain estimates. |
Use with the surrounding model
Select and isolate the flange, pipe or coupling to inspect the open passages. Retain the engine, front structure, clutch housing, gearbox and mounts when comparing obstacles. Their common registration remains estimated; apparent intersections or gaps are model results, not proof of fitted interference or available working room. Intermediate and rear supports are separate estimated comparisons; no fitted front-pipe support is identified.
The front groups separate together for inspection. The source gasket remains in its existing engine display group, and the underfloor reference has its own downward inspection offset. Those choices do not establish what stays attached during service. No manifold/downpipe loosening order, engine support condition, thermal movement, tool access, catalyst procedure or verified extraction path is established.