Brake Master Cylinder 46010-E4602 - Up to 9/1971

[inline6]

It took a while for me to notice, but the master cylinder which came mounted in the engine compartment of the car I am restoring is actually the "later style" which is "incorrect" for the restoration I am doing.  It is this one which is for 240z's from 9/1971: http://www.carpartsmanual.com/datsun/Z-1969-1978/brake/brake-master-cylinder/from-sep-71

The one which was original on my car (6/1971 production) is this one: http://www.carpartsmanual.com/datsun/Z-1969-1978/brake/brake-master-cylinder/to-aug-71

I was able to source one off of eBay that is in surprisingly good shape and I happen to have an old rebuild kit for it which I bought back in the early 1990's:

     

My question is this: given the front and rear circuits are reversed between the two, what do I have to do, precisely to put the original brake master cylinder back in the car so that the circuits are matched up properly?  Or, asked another way, what is typically done to fit the later style cylinder to the earlier car?  I note that these earlier style MC's are nearly unavailable now.  So, I am guessing that people are frequently putting the later style in the early cars at this point.  

I found one relevant thread by searching, but it doesn't have quite the info I need.

 

 

Edited July 9, 2021 by inline6

[texasz]

It your picture the master cylinder has the output for the front brakes in front and for the rear brakes in the rear.  Are you saying that the other master cylinder is different in that the output for the front brakes is in the rear and for the rear brakes is in the front?  If this is the case the modification that is to the lines that come out of the bottom of the master cylinder.  One solution is to bend the existing lines, this has risk of braking/kinking them.  Another solution is to replace the lines from a later Z (this is what I did when I installed the Wilwood 1" which had the outputs swapped from what the stock master cylinder was).  And the last solution is to buy bulk brake line and bend up/make your own new lines (or I think a couple people have used flexible brake hoses here).

 

In your case what you probably want to do is source the original lines from an early car to return to stock...if you are going for stock which it sounds like you are.

 

[CanTechZ]

Not sure if this helps but here are a couple of pictures of my early M/C with the original tubes connected. Hopefully you can compare these to your setup with the later M/C. I replaced mine about ten years ago, probably just before they went NLA.

Edited July 9, 2021 by CanTechZ

[psdenno]

I went through the M/C change on my April '71 built Z 14 years ago and had to use the later style unit. I submitted the same question to the forum members and got great answers.  Please see link below.  It may help you.

 

[inline6]

On 7/9/2021 at 1:17 PM, CanTechZ said:

Not sure if this helps but here are a couple of pictures of my early M/C with the original tubes connected. Hopefully you can compare these to your setup with the later M/C. I replaced mine about ten years ago, probably just before they went NLA.

Yes, that is very helpful.  So, for the later style, you "swap the lines".  Because they are hard lines, I am guessing "swap the lines" isn't literal?  You leave the hard lines in place at the compensator and bend them so they "swap locations" at the master cylinder?

These are pictures from my 240z "track" car.  It is a series 1 with a later style master cylinder on it. 

  

[texasz]

No that is not exactly what I meant.  As I described above, bending the lines to go where you now need them to is ONE solution.  The better solution in my opinion is to grab the lines from the same series (1 or 2) as the master cylinder that way the are already bent to go where they need to go.  Compare your picture above to this one and I think it will become clear.  When the master cylinder changed in 1972 Datsun also made new lines from the master cylinder to the distribution block (again, compare the two pictures).  I hope that this clears this up.  I just did this very swap a few months ago so this is all quite fresh on my mind still.  🙂  

 

[inline6]

12 minutes ago, texasz said:

No that is not exactly what I meant.  As I described above, bending the lines to go where you now need them to is ONE solution.  The better solution in my opinion is to grab the lines from the same series (1 or 2) as the master cylinder that way the are already bent to go where they need to go.  Compare your picture above to this one and I think it will become clear.  When the master cylinder changed in 1972 Datsun also made new lines from the master cylinder to the distribution block (again, compare the two pictures).  I hope that this clears this up.  I just did this very swap a few months ago so this is all quite fresh on my mind still.  🙂  

 

Oh!  Well, that is a bummer because I may not have one of the hard lines I need then.  46221-E4601 for the front, is the one I may not have (#1 here in the "microfiche").  I happen to have a new old stock #2 though. 

    

 

I don't have any pics of these lines on the car I am restoring.  I'll need to grab them and new style MC and a compensator to see what's what.  Whoever fitted the new style cylinder may have bent the existing lines to fit rather than swapping them.  If so, perhaps I can bend the front line back to original shape.

[inline6]

I found the time to pull the lines out of the box of hardware.  Here's what I have:

 

The line which is attached to the compensator is the NOS (new old stock) one.  It is series 1, or per the parts manual up to 9/1971.  The line just to the left is one of two that came with the car.  Other than the bend towards the top, it looks like the same part as my NOS one.  The line at the right in the pic is the other one that came with the car.  It looks very similar to the correct series 1 line for the front circuit, but it won't line up with the correct master cylinder as is.  It would need to be twisted a bit if attached to the compensator to align with the front circuit on the correct master cylinder.  It looks to me like the car still has the original hard lines... that they were tweaked a bit to fit the later cylinder.

[inline6]

On 7/9/2021 at 1:17 PM, CanTechZ said:

Not sure if this helps but here are a couple of pictures of my early M/C with the original tubes connected. Hopefully you can compare these to your setup with the later M/C. I replaced mine about ten years ago, probably just before they went NLA.

Thanks for these pics - again... I was able to reference them and bend my front tube to the appropriate shape using this reference.  I appreciate it.

[CanTechZ]

Your welcome, glad I could help. And thanks in advance for the great references in your build thread. They will help a lot when it comes time for me to re-assemble and as I clean up the parts for my car.

Cheers, Mike

[Captain Obvious]

I'm working on an early master cylinder now. @inline6 How did yours turn out?

I had to resort to drastic measures to get the rear circuit piston out... Anyone got a half dead early master cylinder around they would offer up as parts? I could use one of these:

Also, the valve seats for the output check valves... Mine are stuck in there. How did you get these out?:

 

And just to make searching easier, here are a couple master cylinder related links:
https://www.classiczcars.com/forums/topic/68100-master-cylinder-anomaly/
https://www.classiczcars.com/forums/topic/66276-brakes-dragging/
https://www.classiczcars.com/forums/topic/66168-brake-master-cylinder-identification/
https://www.classiczcars.com/forums/topic/21826-brake-master-cylinder-240z/

 

[Terrapin Z]

 

8 hours ago, Captain Obvious said:

Anyone got a half dead early master cylinder around they would offer up as parts? I could use one of these:

I have this one on HLS30-00903.