YOUR 1975 MIDGET / BLOCK INSPECTION
Find the engine
core plugs.
The 1500 catalogs identify three large cups on the block side, a large and small pair on the block front, and a separate large and small pair on the rear of the head. The CAD shows all seven separately. Their condition and exact positions on this car have not been checked. Use this page to identify what is actually accessible before planning a repair.
Which parts are shown?
| Location | Catalog evidence | CAD status |
|---|---|---|
| Three block-side openings | 144688, nominal 1½ inches (38.1 mm), three on the side | Three separate cups and sockets; centers and depths provisional |
| Block front, large | Moss 328-205; factory 144688 list totals four large plugs | Separate 38.1 mm cup and socket behind the engine plate; center and depth provisional |
| Block front, small | Moss 319-015; factory 144687, nominal 1 inch (25.4 mm), quantity one | Separate cup and socket behind the engine plate; center and depth provisional |
| Head rear, large | 1500-family AEH592, nominal 1⅝ inches (41.275 mm); Midget plate shows one large head cup | Separate rear-face cup and socket; center, depth and fit provisional |
| Head rear, small | 1500-family 144686, nominal 1¼ inches (31.75 mm); Midget plate shows one small head cup | Separate rear-face cup and socket; center, depth and fit provisional |
The factory Midget 1500 parts list ↗ gives 144688 quantity four and 144687 quantity one. The Moss external-engine plate ↗ shows three large side plugs and a large/small pair at the front. Together, these support the distribution shown here; the mapping between catalog number systems is inferred. Rimmer's 144688 listing ↗ identifies the large nominal diameter. A Spitfire MkIV restoration photo ↗ shows a side row on a related engine, not proof of this Midget's fitted casting.
The head has a separate rear pair
The Midget 1500 head plate ↗ shows one large and one small cup. The 1500-family head catalogue ↗ lists AEH592 at a nominal 1⅝ inches and 144686 at 1¼ inches. A Moss replacement listing ↗ calls its large cup 1 41/64 inches. Those different nominal labels are a reason to measure the clean fitted opening and removed cup; neither is an installation interference specification.
The CAD positions both cups on an estimated rear face of the head and leaves their sockets open. It does not establish this car’s head variant, exact centers, wall depth, rear access or a removal route. Photograph the whole rear head and both openings with a scale if a planned repair exposes them. See the pair in CAD ↗
What to record on this car
- 1 · IdentifyWith the engine off and fully cool, locate each visible cup along the block side. Photograph the whole side and then each plug with a nearby fixed feature. Note anything that hides a position.
- 2 · Separate observationsRecord rust, staining, wetness and nearby hose or gasket traces at each location. A wet area near a cup does not by itself establish where coolant began leaking.
- 3 · Measure when exposedWhere a raised metal seat is accessible, measure its outside diameter and projection from the adjacent block face. Enter them for that specific plug in the CAD inspector to reshape only that seat in an owner STEP. If a repair has already required plug removal, also measure the clean opening and removed part before selecting a replacement.
The engine stamp recorded for this car is FP4025UE. Keep a photograph of that stamping with the plug record so any parts comparison can be tied back to the fitted engine. The three virtual side centers have not been derived from this stamping.
The two front plugs are behind the engine plate in the assembled study. If a real repair exposes that area, photograph the plate, both openings and any intervening gasket or cover with a scale before removing a plug. The CAD does not establish a front-plug access or extraction sequence.
The rear head cups may be hidden by bodywork and other fitted parts. Do not assume that the virtual open rear view represents an in-car extraction route.
Before a repair plan becomes a procedure
Confirm which plug is leaking, which adjacent parts prevent straight access, and whether the block-side opening can be worked on in the car. Obtain the applicable North American 1975 factory procedure and its coolant, seat-preparation and installation instructions. The CAD is useful for naming parts and planning photographs; it does not establish a safe extraction angle, drive tool, sealant choice or finished interference fit.
Read the CAD accuracy limits ↗ · Return to the cooling check ↗