SP 250 dual circuit breaks

Descriptive and in-depth articles on how to do repairs or restoration.
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Warsash 2
Posts: 178
Joined: Sun Feb 28, 2016 1:53 pm

SP 250 dual circuit breaks

Post by Warsash 2 » Tue May 24, 2016 10:17 pm

HI
An attempt to upload an article. Some of the suppliers may not still be in business
Attachments
Slide1.jpg

New Dexter
Posts: 314
Joined: Fri Feb 12, 2016 9:41 am

Re: SP 250 dual circuit breaks

Post by New Dexter » Wed May 25, 2016 7:35 am

The word is brakes, not breaks

David S
Posts: 153
Joined: Sun Feb 21, 2016 9:23 am
Location: Forest of Dean

Re: SP 250 dual circuit breaks

Post by David S » Wed May 25, 2016 2:18 pm

I think dual braking is a worthwhile modification, having needed it on one occasion!

So, to help, I have looked up in my Lucas book the part number for the various master cylinders you quote. It would be helpful to know the actual vehicles part when ordering as there are a few mods in the car's lifetimes as you will see.
The 3500 P6 Rover had PMH 203 master cyl, PMH 199 was in 2200 & 2200TC. There is no list in my book for the Rover 2000.
For 1980's Mazda 323 it shows many variants:
1000, 1300 & 1400 [1977-1982] had PMF 253 master Cylinder.
Later 323 cars [1981-85] 1100, 1300, 1500 & GT used PMF 284.
The series iii facelifted Mazda 323 [1986-89] 1500 estate, 1.3 & 1.5 cars had PMH 362
The Mazda 323 1600i had a PMH 342 master cylinder.
My Lucas book does not list Aston Martin DB4.
I don't know the differences, they could be very minor, but as I said it would help to know just what you used.
I hope this helps in some way...

Warsash 2
Posts: 178
Joined: Sun Feb 28, 2016 1:53 pm

Re: SP 250 dual circuit breaks

Post by Warsash 2 » Wed May 25, 2016 7:45 pm

Hi Dave
I bought the master cylinder at the NEC so I did not get a receipt, cast on the side is 1.22 and A & B on the outlets. However if you try the the supplier I named he claimed he had provided quite a few. It definitely came off a P6 Rover european export model. I think it's from a 3,500. The Mazda ones were used in Australia and I have no idea which model. Whilst the Rover fits with out modification the Mazda one needs some alteration to the holes and the rod length. I have no idea about the DB4 fitting. I found the P6 club very helpful and the gave me a diagram for fitting a servo if required. We did not use it but I enclose a copy below.
To Dexter
I am glad you found 1 of the deliberate mistake what happened to the rest?
Regards
Colin
Attachments
P6 Diagram.jpg

Warsash 2
Posts: 178
Joined: Sun Feb 28, 2016 1:53 pm

Re: SP 250 dual circuit breaks

Post by Warsash 2 » Wed May 25, 2016 9:56 pm

Hi
I have just looked out close up of the master cylinder which I attached. I should have mentioned that the fitting and balancing of the P6 servo System is a bit of a pig to do. We have not found the need for a servo even in our advancing years.
Regards
Colin
Attachments
Master Cyinder1R.jpg

Crossley Stephenson
Posts: 164
Joined: Wed Feb 10, 2016 9:15 pm
Location: Victoria, Australia

Re: SP 250 dual circuit breaks

Post by Crossley Stephenson » Thu May 26, 2016 9:23 am

I am investigating converting to dual circuit brakes and have read the articles by Colin Jordan & Matthew Waterhouse plus researched the Old Forum where there is a lot of info. Some of the SP guys here in Oz used a Mazda 323 tandem mc but it required some machining to make it fit. I see that SteveW62 & Dovr both used a mc from a Datsun 120Y - hope they read this - but I don't know whether it required any alteration to make it fit, ie do the holes line up for fitting? It is also 11/16" rather than 3/4" - does this matter?

Cheers
Michael

dovr
Posts: 2
Joined: Mon Feb 22, 2016 7:51 pm

Re: SP 250 dual circuit breaks

Post by dovr » Sat Jun 04, 2016 9:14 pm

Hi Michael

The Datsun unit is a direct swap, the only mods were to improve access to the bleed nipples on the side. The smaller bore gives slightly more pressure to the caliper (non servo system).

I think the pipe threads are metric, which wasnt a problem as it needed new connections.

Cheers



Dov

Crossley Stephenson
Posts: 164
Joined: Wed Feb 10, 2016 9:15 pm
Location: Victoria, Australia

Re: SP 250 dual circuit breaks

Post by Crossley Stephenson » Sun Jun 05, 2016 7:16 am

Thanks Dov.

Michael

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