GT brake master cylinder

[Orrp01]

Anyone know the Girling part no for master cylinder repair kit mark 2 gt, or does the club have any? Even better would be a new master cylinder if available ty Phil

[thomas]

Anyone know the Girling part no for master cylinder repair kit mark 2 gt, or does the club have any? Even better would be a new master cylinder if available ty Phil

I think, assuming it's the single-circuit setup, the Girling kit is coded SP2381, the equivalent Moprod is M2381. There are a few on ebay at wildly varying prices at the moment. Club Spares will be sure to have some.

The sort of coffee-lid rings that hold the reservoir extension on to the master-cylinder body rust badly and it would be a brave man who splits the two, though the seal for between them is in the kits too, it isn't strictly necessary to split them to replace the piston seals. I've seen the smaller size of reservoir extension ring such as is fitted to the FD Victor available from aftermarket suppliers in solid aluminium, but none for this larger size extension as found on disk equipped HBs, including the GT.

The master cylinder itself, a Girling 812 (812 refers to the bore size, 0.812 inches) was fitted to some Fords, Escorts and stuff too. Dual-circuit front-rear split seems the way to go if upgrading the system, but finding a dual-circuit master-cylinder that is going to bolt straight onto the existing Girling Supervac servo, except by costly trial-and error, is the difficult part. Many HB owners seem to have successfully utilised the later Viva HC type of servo/master-cylinder on their cars.

Below is a link to the (pretty sparse) instruction leaflet that should come with the SP2381 kits, though it doesn't show the exterior of the larger body m/c or its larger reservoir-extension, it is otherwise the same internally:

[Orrp01]

Thanks for info, exactly what I wanted to know. Inside of reservoir was full of gunk so wanted to remove it to properly clean. The ring was really badly rusted so I removed it and yes it did get damaged so could do with one if there are any out there.

[thomas]

This is the sort of thing, but is the wrong size, is too small. No-one seems to make the larger ring/collar needed for the original disked HB m/c any more, if anyone ever did.

https://www.demon-tweeks.com/uk/girling ... spb000317/

Further information I have gleaned - not 100% reliable, and highly specific to certain year/month ranges - is that the same or equivalent 0.812 (13/16 inch) master, was also used on FORD CAPRI Mk1 3.0 litre GXL, and the EARLY FORD ZEPHYR & ZODIAC MKIV RANGE, APPROX 05/1966 TO 07/1968.

You might get lucky and find a complete master cylinder on ebay with the plastic bottle and retaining collar, they were not ever supplied separately but only with a complete master-cylinder. Unfortunately I can't see any there at the present time.

[jpsmit]

If you are stuck I think I have one - not pretty and dual brake system but available.

[thomas]

One of these has now turned up on ebay:

Listed for a Cortina/Zephyr

https://www.ebay.co.uk/itm/392087759835 ... 2087759835

The pictures don't show it end-on, so it is impossible to tell if the plunger/piston is present or not. Unmolested NOS should have a temporary rubber cap over the end of the cylinder bore, which appears missing.

[Bob perry]

The one on e. bay looks a bit expensive for a gamble!!
Give Fred a try first, but I managed to get a Master Cylinder from Merlin Sports at Castle Coombe in Wiltshire, ( race specialists situated on the Castle Coombe race circuit ), or Power Track Ltd., both really good with brake stuff. Good websites for both.

[jpsmit]

I have to say the scan looks an awful lot like this:

https://mossmotors.com/master-cylinder-aftermarket-1

Spitfire uses the same Girling calipers so the diameters should be the same.

[thomas]

The one on e. bay looks a bit expensive for a gamble!!

It's also very manky, even if it is fifty years old!

If you think that's expensive, look at this (possible alternative) one:

https://www.ebay.co.uk/itm/291105320358 ... 1105320358

[thomas]

I have to say the scan looks an awful lot like this:

https://mossmotors.com/master-cylinder-aftermarket-1

Spitfire uses the same Girling calipers so the diameters should be the same.

Superficially it might, but as explained in the text further up, the scan doesn't show the actual master-cylinder in question, it has a much wider bowl too, as well as the larger extension bottle. I don't think the one you linked to would displace enough fluid volume due to the likely smaller bore and might not have enough reserve capacity to cope with the full range of possible pad wear. They (Vauxhall) must have had their (good) reasons for fitting this considerably meatier and costlier than standard master cylinder. I have seen on ebay an HB which the seller stated had disk brakes on the front, but it was without servo and it had the original tiny bulkhead-mounted master-cylinder, which made me feel ill-at-ease, just viewing the pictures. The ones we're considering too, the mounting bolts are horizontal. It looks like this:



However there are lots of possible alternatives out there, such as the pricy Escort one linked above, and possibly the Canadian model type too would be an ideal upgrade, it's just finding out what works, preferably using others as my guinea pig test-pilots. I've got several service kits stashed, and a mint boxed 812 as a spare, but might still want to go dual-circuit in the future. In this instance, safety and best practice trump originality. If going aftermarket it would be as well to see what the service kit availability for your shiny new one is now and what it might be in the future, and stock-up on a couple of service/seal kits for that in advance while you can too.