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MG Midget and Sprite Technical - 7lb longneck Radiator Cap, part No's

Here’s a scan of a page in a Quinton Hazel parts catalogue. It shows the exact dimensions of some various caps of the day.

For us the significant one is the FC41A.

This is the correct QH part number for the long neck 7lb cap fitted to vertical flow Radiators.

The FC41A often gets confused with the FC41 which then gets supplied in error. The FC41 is the SHORT neck version. It's also 7lb. It was specified for many A series engined cars amongst others, BUT NOT for the Spridget.

As you can see from the picture, the two are easily distinguishable by measurement from the outside of the cap, to the outside of the vacuum release valve. The long neck FC41A is 34mm, as opposed to the short neck at 25mm.



Some equivalent part numbers to the FC41A are:

GRC101. – Not to be confused with GRC110, which is the 15lb cap for the expansion tanks on the later 1275 and 1500 x-flow radiator setups.

FRC64. This is made by First Line who claim OE quality. I bought one. It’s well made.

CHT105 From AH spares. Don't know what make this is.

There are no doubt plenty more, so if you get, or know of a long neck 7lb radiator cap with a different part number, perhaps you could add to this thread.


Lawrence Slater

excellent stuff, well done Lawrence

though even more confusing as FC41 shows as 4 psi on that chart(?)
N Atkins

Yup, well spotted Nigel. I had just taken previous note that the incorrect short neck was fc41 at 7lbs. You're right that's a 4lb cap.

Actually the 7lb short neck can be GRC102, or AC delco RC4 for example.

So if you mistakenly receive or order FC41, you will indeed get a shortneck 4lb cap.


So to reiterate.

For the Vertical Flow Radiator, you should order and receive a long neck 7lb cap, 34mm long, measured from the outside of the cap to the outside of the vacuum relief valve.

Known part numbers so far:

Some equivalent part numbers to the FC41A are:
GRC101
FRC64.
CHT105
Lawrence Slater

someone would have mentioned it so it mught as well have been me :)

good work though

to repeat and keep info at top of thread:-

For the Vertical Flow Radiator, you should order and receive a long neck 7lb cap, 34mm long, measured from the outside of the cap to the outside of the vacuum relief valve.

Known part numbers so far:

Some equivalent part numbers to the FC41A are:
GRC101
FRC64.
CHT105
N Atkins

This thread was discussed between 18/10/2011 and 19/10/2011

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