Fan Blade bolts

[KeithL]

Can anyone confirm the specification of the the 4 bolts holding the fan blade and pulley onto the water pump on a MM 1000 1098cc engine - length, diameter, thread and whether the bolts are 'special' in any way?

The list on the forum says the thread should be 1/4" UNF but that is for a Series II and I wasn't sure if that changed on the 1000.

I'm not sure my bolts aren't catching the water pump and the one I took out was very, very stiff and the thread seemed damaged which made me wonder if the thread was right.

[les]

I think you'll find they are 1/4" bsf the length is approximately 3/4" fitted with spring washers. They are just regular type.

[philthehill]

The thread for the set screw (bolt) in question is 1/4" UNF.
The length of the set screw is 3/4".
The body casting behind the pulley and fan mounting boss can vary dependent upon supplier so you do need to check for clearance behind the boss.

[RobThomas]

Might be BSF on the SV engine, though. I know the Morris 8 ones don't fit the 1098.

[IslipMinor]

but that is for a Series II

The list is for the Series II and later - it is NOT for the MM.

[RobThomas]

Bolt pattern for the MM is the same, isn't it? I've a sneaking feeling that the shaft is the same diameter, too.

I may be wrong on this. Worth maybe taking some measurements?

[IslipMinor]

By 'MM' I mean the side valve first series of the Minor.

I have no information on them, other than I believe some of the fixings have metric threads and BSF/BSW hex head sizes - or is that just an urban myth?

[philthehill]

Richard
Bolts with metric threads with Whitworth heads - not an urban myth but a reality.
Some engine studs also had metric threads with metric threaded nuts which used Whitworth sized spanners.
A left over of Morris taking over the Hotchkiss engine works Coventry in 1919 with their metric calibrated machinery and the lack of metric spanners in the UK garage trade.

A similar situation arises with the use of American Unified National Special (UNS) which I believe to be a left over from Morris at one time using White and Pope engines and Continental of Detroit engines.
During the inter war years Hotchkiss also made a copy of the Continental engine at Coventry.

Whilst the classification of 'Unified Threads' did not happen until 1948 many of the original threads continued with the same specification even after being classified as Unified.
Phil

[Declan_Burns]

The XPAG engine on my MG TD has has the so called "Mad metric" bolts and studs with metric fine thread and Whitworth heads.
Phil is correct, it is not a myth.

Regards
Declan