thread identification sp250

[daimlersteve]

Here's one for the techo's out there --- The thread at the top of the carbs. damper chamber ----

steve

[Vortex O'Plinth]

Tricky one! Its near (but slightly larger) than 3/8" BSP. Burlen Ltd might be able to tell you.

[daimlersteve]

Com'on men, i thought i'd get more suggestions !!
It seems to be 17x1 mm.
Strange, but then i was told today that a Morris engine in the thirties was all metric for two years before going to all brit.

A new trial tubular manifold using the std carb centerpiece and alloy flanges has yielded more power and further enhanced throttle response. quite pleased with the outcome , must be up 'round 195 hp ( 153@ the wheels with leaking gasgets now sorted)with a 300 rpm idle and pull from there up.

[David S]

Morris was metric for more than 2 years, indeed for the whole run of 10-4 cars [1932-35] the engines have metric threads. I think others had a longer production life and WW2 finished the idea off. I think it is something to do with Morris' relationship with the French firm Hotchkiss.
It is not so easy though, as the threads have a fine pitch and are non-standard, many are M8x1 [the normal M8 pitch is 1.25], but their hexagon heads are Whitworth spanner size! In all it is a bit of a maze.
I sometimes think I'll convert all mine to allen screws!

[Vortex O'Plinth]

Morris was metric for more than 2 years, indeed for the whole run of 10-4 cars [1932-35] the engines have metric threads. I think others had a longer production life and WW2 finished the idea off.....

Not quite David. My 1948 MG TC engine has metric threaded bolts with Whitworth heads. This late thirties designed Hotchkiss XPAG engine was fitted to several MG, Morris and Wolseley cars (many parts are stamped with the ubiquitous 'MOWOG' - MOrris, WOlseley and MG). Rather than change all the original Metric fasteners on the engine to Whitworth, the metric thread was retained (to save redesign and tooling costs) but special Whitworth headed hybrid bolts were produced to allow owners to use their 'standard' Whitworth spanners throughout the car. These 'bastard' fasteners have caught out many unwary owners over the years and mangled threads are often encountered during a rebuild of these engines.