9 replies to this topic

[no66]

Hi,

time to get going again and get this thing on the road.

My "Norwegian" 1972 Austin 1000 has the older front/rear split master cylinder (round res) As it is so old and has worn out clevis pin fork, I want to replace it. 

I was thinking of a new:

BRAKE MASTER CYLINDER 1980-89 (YELLOW IDENTITY TAG) GMC227
https://www.minispar...ow-identity-tag

and LHD pipe kit
https://www.minispar...sion-for-gmc227

This should work right?  

 

 

 

[Ethel]

If it's just the fork, you should be able to replace just that. Also look at the hole in the pedal.

 

The Minispares diagram shows those pipes with the FAM7821 valve that's fitted on the bulkhead, so the answer will be yes if you have one of those. If you don't, the pipe unions are M10x1 which won't fit the UNF unions that were used previously.

 

Note the FAM7821 is not the same as the PDWA that had an electrical connection for the failure warning switch.

[no66]

If it's just the fork, you should be able to replace just that. Also look at the hole in the pedal.

 

The Minispares diagram shows those pipes with the FAM7821 valve that's fitted on the bulkhead, so the answer will be yes if you have one of those. If you don't, the pipe unions are M10x1 which won't fit the UNF unions that were used previously.

 

Note the FAM7821 is not the same as the PDWA that had an electrical connection for the failure warning switch.

Ah thanks for this info.
Pedal is ok, its the fork. Same to the clutch, so will be replacing that too. 

As for Master, it 53 years old, and a bit of rubber in the fluid, so seals are problably shot. From what I understand, seals are hard to get and dismantling also very hard. 

Yes it is older PDWA block so I will need metric unions for the new GMC227 master and UNF for the PDWA. Have a flaring tool and pipe. 

 

Edited by no66, 19 January 2025 - 04:25 PM.

[Spider]

 

If it's just the fork, you should be able to replace just that. Also look at the hole in the pedal.

 

The Minispares diagram shows those pipes with the FAM7821 valve that's fitted on the bulkhead, so the answer will be yes if you have one of those. If you don't, the pipe unions are M10x1 which won't fit the UNF unions that were used previously.

 

Note the FAM7821 is not the same as the PDWA that had an electrical connection for the failure warning switch.

Ah thanks for this info.
Pedal is ok, its the fork. Same to the clutch, so will be replacing that too. 

As for Master, it 53 years old, and a bit of rubber in the fluid, so seals are problably shot. From what I understand, seals are hard to get and dismantling also very hard. 

Yes it is older PDWA block so I will need metric unions for the new GMC227 master and UNF for the PDWA. Have a flaring tool and pipe.

 

Are Clevis's ('Fork') available new for any Master Cylinder ?

 

Originally, the car would have been fitted with the earlier type of pressure shut off valve in the rear subframe. The GMC227 Master will work fine with that and I'd actually suggest sticking with it rather than going over to the FAM7821.
 

[no66]

 

 

If it's just the fork, you should be able to replace just that. Also look at the hole in the pedal.

 

The Minispares diagram shows those pipes with the FAM7821 valve that's fitted on the bulkhead, so the answer will be yes if you have one of those. If you don't, the pipe unions are M10x1 which won't fit the UNF unions that were used previously.

 

Note the FAM7821 is not the same as the PDWA that had an electrical connection for the failure warning switch.

Ah thanks for this info.
Pedal is ok, its the fork. Same to the clutch, so will be replacing that too. 

As for Master, it 53 years old, and a bit of rubber in the fluid, so seals are problably shot. From what I understand, seals are hard to get and dismantling also very hard. 

Yes it is older PDWA block so I will need metric unions for the new GMC227 master and UNF for the PDWA. Have a flaring tool and pipe.

 

Are Clevis's ('Fork') available new for any Master Cylinder ?

 

Originally, the car would have been fitted with the earlier type of pressure shut off valve in the rear subframe. The GMC227 Master will work fine with that and I'd actually suggest sticking with it rather than going over to the FAM7821.
 

 

Thank for the info, yes It has the inetia type rear pressure valve. 

[Ethel]

"Are Clevis's ('Fork') available new for any Master Cylinder ?" They do exist, but for daft money compared to a whole new cylinder, an "experienced" one could be lying around though & they're reasonably generic, or a bit of weld & redrilling could sort the original. This is interesting though 

 

 

Making up your own lines is a good option. The top port on a GMC227 is a straight forward m10x1; the bottom is M12x1 which will take a bit more effort to source. You want a 3/16" bore, not 1/4". 

 

https://www.burtonpo...vroPfw1BIiZ7Qbn

[Spider]

"Are Clevis's ('Fork') available new for any Master Cylinder ?" They do exist, but for daft money compared to a whole new cylinder, an "experienced" one could be lying around though & they're reasonably generic, or a bit of weld & redrilling could sort the original. This is interesting though

 

Thanks Ethel. I have looked, unsuccessfully in the past for the Clevis (and Pushrod), but rarely come up with anything. Repairing them as you've suggest might be an option, though I have considered that, time has never been on my side to do this.I have seen though ends from CBS (and others), I must grab some next time I order !

[no66]

Making up your own lines is a good option. The top port on a GMC227 is a straight forward m10x1; the bottom is M12x1 which will take a bit more effort to source. You want a 3/16" bore, not 1/4". 

Yes, can source 10x1 here in Norway, but harder finding 12x1. Might just get the line kit from MS just for the 12x1 union.

Was thinking of welding and drilling the fork, but as mentioned, this is a 53 year old master, not worth the risk. 

What do you mean by " You want a 3/16" bore, not 1/4". ?

Edited by no66, Yesterday, 08:44 AM.

[Ethel]

The pipe size. Brake pipes are 3/16. 12mm is big enough to fit 1/4 inch pipe, but a fitting for 1/4 pipe won't support or tighten properly on 3/16. M12 unions also come in various thread pitches as they're common for stuff like diesel fuel lines, something else to watch out for. You should be able to find 12x1 for less than the pipe set, but paying 2 lots of postage could wipe out the difference.

 

I use a Metro clutch master, which is 12x1 too. I made up a steel insert to simply things: I'm also using a braided hose with banjo fittings. Pretty sure m10x1 helicoils will be 12x1 - that'd be another solution.

[Spider]

You can get M12 fittings for 3/16" Tube, eg;-

 

https://www.carbuild...ec37a6914&_ss=c

 

and M12 to M10 Adaptors should one wish to go that way;-

 

https://www.carbuild...ec37a6914&_ss=c

 

The fitting kit from Mini Spares if I recall has the former.