70 Z Brake Master Cylinder Problem - Repair or Replace (and with what?)

[Namerow]

Today, I started on what I hoped would be the straightforward job of rebuilding the brake master cylinder for my 70 Z.  Disassemble, clean, install new seals and hardware, and reassemble.  Job done.  What could go wrong?

Unfortunately, I only got to Step 2.  After cleaning things out, I found a little divot in the floor of the cylinder bore, located about 1/2" aft of the rear stopper bolt.  Hard to say what cause it.  The car has been sitting for many years so I guess it corrosion damage.  It's about 1/8" in diameter and deep enough to catch my fingernail on. The rest of the bore is in great shape.

When I look at the cross-sectional view of the Brake MC in the 71 FSM, I see that this divot sits pretty much mid-way between the front and rear seals of the rear piston.  Knowing that, it doesn't seem like the seals stand a chance of being nicked by it.  Nor do the rear piston and seals that came out of the cylinder look like they've been hurt by it.

So - Question 1:  Can I get away with just leaving it as-is?

If the answer is that it's going to be ok to ignore it, then I've still got a minor problem in that that the rebuild kit that I bought a number of years ago is not suitable for the 70 - 71 brake MC -- different seal types (even though the bore is the same).   That leads to...

Question2:  Anybody know where I can get a rebuild kit for the 70-71 MC?

If the answer to Question 1 is 'MC must be replaced', then I've got a much bigger problem.  The 72 MC, while an improved design, has the front and rear reservoirs and lines flipped around -- which means that my hard lines won't fit.  Plus, a 72 MC would dilute the 70-ness of the car's engine compartment (a small but touchy consideration).

MSA lists the early-design Brake MC as NLA.  The typical parts suppliers also show 'NLA'.  Then there's Rock Auto...

Rock Auto shows NLA for 70, but lists two units for 71.  One is from Cardone, the other from Centric.  When I look at their 72 listings, there are about 6 choices, including Cardone and Centric.  The 71 and 72 Centric units have the same PN, so that one's undoubtedly the 72 design.  The  71 and 72 listings for the Cardone units, however, show different PN's.  In addition (although this may mean nothing), the pop-up picture of the 71 Cardone unit shows the 70-71 design, with the 'F' line/reservoir at the front and the 'R' reservoir/line at the rear.

Question 3:  Does anyone have any experience with the Cardone unit listed under '1971' from Rock Auto?  Could it possibly be the real deal? (i.e. the 70-71 design).

If these 70-71 brake MC's truly are NLA from anywhere, what do members recommend as a remedy.  Am I really going to have to fit new hard lines? or...

Question 4:  If I am forced to fit a later-style 72 MC, does anyone know if I can install the internals from my 70 MC into a 72 casting , thereby keeping the reservoirs/lines in the correct, 70-71 orientation?  Both castings have a 7/8" bore and -- other the placement of the stamped 'F' and 'R' markings -- I think they may be identical.  Intuition suggests that the factory would have made efforts to keep the same casting when they upgraded the design, limiting the changes to the internals (and the hard lines).

[Mark Maras]

 The "divot" is common in old cylinders. If the seals won't contact it during their stroke and if you can get an installed seal past the divot without damaging it, IMO you're good to go. I'd consider the repair as a temp and give me time to source a new one.

What is the difference between the old and new seals?

 

[grannyknot]

John, you might want to contact Raff,(CARELESS) he'll know for sure and may have some spares even.

[psdenno]

If keeping the 1970 style master cylinder is important to you and you don't mind spending a bit more than the cost of a '72 replacement MC, give a call to White Post Restorations.  They can resleeve your '70 MC with a stainless steel insert and give you a lifetime warranty.

Dennis

[Namerow]

15 hours ago, Mark Maras said:

 The "divot" is common in old cylinders. If the seals won't contact it during their stroke and if you can get an installed seal past the divot without damaging it, IMO you're good to go. I'd consider the repair as a temp and give me time to source a new one.

What is the difference between the old and new seals?

 

Thanks, Mark.  This might prove to be my only option for the time being.  I've now verified that the 72 MC casting is quite different from the 70-71 design, so -- even though the bore size stayed at 7/8" -- the 70-71 internals do not look like they'll line up with the internal orifices.  Also, not only are the hard line connections reversed from F-R to R-F, the spacing of the two lines is about 1/2" different, too.

Unfortunately, in the 12-hour period since my original posting, the Rock Auto listing for the Cardone 71 unit has gone from 'available' to 'out of stock'.

I'll upload a picture of the pistons and seals from my 70 MC soon, along with a picture of the deals that came in my rebuild kit.  The seals for the 70 MC are much 'wider'.

13 hours ago, grannyknot said:

John, you might want to contact Raff,(CARELESS) he'll know for sure and may have some spares even.

Thanks, Chris.  I'll give him a try.

 

10 hours ago, psdenno said:

If keeping the 1970 style master cylinder is important to you and you don't mind spending a bit more than the cost of a '72 replacement MC, give a call to White Post Restorations.  They can resleeve your '70 MC with a stainless steel insert and give you a lifetime warranty.

Dennis

Thank you, Dennis.  I knew that there were MC service specialists out there and that sleeving could be a possibility.  With your recommendation in place, I'll check these folks out.  Depending on cost, this might be a good option.  I'm concerned that there aren't enough 70-71 MC cores floating around out there to provide the rebuild businesses with a basis for re-stocking the suppliers' shelves.  Maybe no seals available either.

[Patcon]

psdenno

I saw they're website. Any idea of the cost to sleeve a master cylinder?

[psdenno]

1 hour ago, Patcon said:

psdenno

I saw they're website. Any idea of the cost to sleeve a master cylinder?

It's been a couple years since I asked them about the cost of sleeving the MC for a Porsche 911/914 and they faxed a quote to me.  Can't find that paperwork now but will keep looking.  Maybe around $300, but that's a guess and could be way off.  

Dennis

 

 

[Patcon]

$300 is doable considering the last time I saw an early MC it was mid $200's or higher...

[Namerow]

With very little effort, I've now found a brake MC service specialist that's located just 10 miles away from me.  I'm going to ask them for a quote on a bore-and-sleeve repair and will post the amount here for the possible interest of others.  It will be in Canadian dollars, though, and won't necessarily translate into what one might pay for a similar job done by a shop in the US.