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A One Inch Diameter Brake Master Cylinder for the S30 Z Cars

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A One Inch Diameter Brake Master Cylinder for the S30 Z Cars

 

 

With the availability of the 280ZX 15/16 inch diameter master cylinder becoming limited there is now another option for a larger diameter master cylinder for the 1970-78 (S30) Z cars. Wilwood, long known for their automotive racing products, now makes a one inch diameter master cylinder that is almost a “bolt-onâ€, requiring only two minor modifications.

 

 

Why use a larger [one inch] diameter master cylinder?

 

The diameter of the brake master cylinder is determined primarily by the amount of fluid displacement that is required to move the caliper pistons against the brake pads so they contact the rotor surface. Other minor factors, such as the brake pedal lever ratio and the brake booster size, may be considered as well.

 

The diameter of the stock master cylinder on the 1970-78 Z cars is 7/8 inch. When Nissan introduced the 280XZ in 1979 they changed the brake system by going to disc brakes at the rear and added a vented rotor up front along with a floating caliper. The rear calipers and the new front calipers required more fluid and hence Nissan increased the diameter of the 280ZX master cylinder to 15/16 inch.

 

Brake modifications to the 1970-78 Z cars typically involve changing the rear brakes from drums to discs with calipers replacing the rear wheel cylinders. The front calipers are changed from the stock two-piston to a four (or six) piston one with increased piston area. Both of these changes require more fluid from the master cylinder and the change to a larger diameter master cylinder is always recommended as part of the brake upgrade.

 

The 280ZX 15/16 inch diameter master cylinder is typically used for the S30 brake upgrade, but as the supply of good used 280ZX master cylinders becomes scarce and the cost of NOS ones quickly increasing, going to an aftermarket one inch diameter master cylinder is a viable option. However, a larger diameter master cylinder will require more pedal force to build the same fluid pressure. Nissan used a larger diameter brake booster on the 280ZX to reduce the pedal force of the 15/16 inch diameter master cylinder.

 

 

The Wilwood one inch master cylinder

 

The Wilwood one inch diameter master cylinder which will work on the S30 Z cars is Wilwood part number 260-8794. There is also a 260-7563 part number which is the one inch diameter master cylinder but with remote reservoirs. The remote reservoir kit makes the 260-7563 slightly more expensive than the 260-8794.

 

http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-8794

 

http://www.wilwood.com/PDF/DataSheets/ds439.pdf

 

The Wilwood one inch diameter master cylinder is available from Jegs, Summit, StreetPerformance.com, and probably others.

 

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Modifications needed

 

The Wilwood one inch master is a “vertical mount†type and although it initially appears to fit the S30 brake boosters as is, you have to do a modification to it first. The center-to-center spacing on the S30 booster mounting studs (for the master cylinder) is 60mm whereas the bolt hole spacing on the Wilwood one inch master mounting holes is 57.2mm (2.25 inches). So, you will have to elongate (slot) the mounting holes on the Wilwood master with an end mill or a file. You could also drill out the mounting bolt holes (on the Wilwood master) to the next larger drill size.

 

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The second modification allows the Wilwood one inch master to connect with the S30 brake lines. The Wilwood one inch master cylinder outlets are designed to be used with standard 3/16 inch SAE double flare brake line fittings which have 3/8-24 threads. However, you need 10mm x 1.0mm female metric threads to interface with the stock Nissan double flared brake lines.

 

Fortunately the SAE threaded outlet fittings on the bottom of the Wilwood master cylinder can be unscrewed and replaced with the Nissan metric ones off your old stock master cylinder. However, this only applies if you have a 1972-78 stock master cylinder as your donor.

 

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The outlet fittings of the 1970-71 stock master cylinders are different and will not fit the Wilwood master. This also applies to most the aftermarket (i.e., the non-Nabco/Tokico ones) S30 master cylinders.

 

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The stock outlet fittings on the bottom of the Nissan master cylinder are part number 46038-B5012 which is still available from Courtesy Nissan:

 

http://www.courtesyparts.com/cylinder-p-p-362085.html

 

Note: Tighten the outlet fittings on to the bottom of the Wilwood master cylinder with 156 in-lbs of torque.

 

If you cannot locate suitable metric outlet fittings, then you can resort to cutting the metric fittings off your stock brake lines, installing 3/8-24 fittings, and re-flaring the ends of the lines. No manufacturer (that I am aware of) makes a single-piece 10mm x 1.0mm to 3/8x24 UNF brake line adapter.

 

 

Residual pressure check valves

 

According to the Wilwood 260-8794/260-7563 instruction sheet, the Wilwood one inch master cylinder contains internal residual pressure valves (for drum brake use only) which should be removed and not used in disc brake applications.

 

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Adjusting the booster pushrod

 

The push rod projects from the front of the brake booster and activates the master cylinder pistons. The push rod length is adjustable and the push rod to master cylinder piston clearance (gap) should be checked any time the master cylinder or booster is replaced.

 

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Problems can occur if the push rod is improperly adjusted. If the gap is too small (or non-existent) then the master cylinder piston will not return completely when you let off the brake pedal and there will be pressure remaining in the lines which will result in brake drag and premature pad wear. If the gap is too large then there will be a slight time delay in brake actuation, increased pedal travel and reduced pedal travel reserve distance.

 

The preferred push rod adjustment procedure is to use a special tool or gauge to determine the gap. However, if such a suitable tool is not available then an alternate method can be used (see the accompanying pictures).

 

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Using a vernier caliper, measure the distance between the rim of the master cylinder bore to the mounting flange surface on the master cylinder (measurement “Aâ€).

 

Measure the distance between the bottom of master cylinder primary piston to the top of the rim of the master cylinder bore (measurement “Bâ€).

 

Subtract A from B to obtain the depth of the master cylinder primary piston to the mounting flange surface (measurement “Câ€).

 

On the booster place a precision straight edge across the face of the master cylinder mounting surface adjacent to the push rod. Measure from the top of the straight edge to the top of the push rod (measurement “Dâ€).

 

Measure the width of the straight edge (measurement “Eâ€).

 

Subtract D from E to obtain the height of the push rod (measurement “Fâ€).

 

The push rod clearance (or gap) is determined by subtracting F from C. Adjust the push rod to obtain 0.3mm (+/- 0.2mm) of clearance.

 

Warning: When adjusting the push rod length avoid pulling the push rod out of the booster to prevent the reaction disc from falling down into the booster. The best way to prevent this is to place the booster facing up when adjusting the push rod length. If that is not possible (i.e., booster is bolted to firewall) then apply moderate pressure on the push rod in a direction towards the booster during the adjustment which will keep the reaction disc from moving.

 

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Appendix/Addendum

 

* The stock Nissan reservoir caps will fit on the Wilwood reservoirs. Likewise, the Wilwood reservoirs appear to be identical to the Nissan stock ones so that they will even fit the stock master cylinder. The Wilwood part number for the reservoir is 260-3386.

 

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* The Wilwood master cylinder has o-ring sealing where the reservoir mounts, a nice improvement over the stock master.

 

* Use silicone sealant to seal the base of the master cylinder to booster as it should be an air tight seal.

 

* Tightening torque for brake line fittings. As a general rule tighten the nut finger-tight until you feel it draw down tight, then tighten with a brake flare wrench approximately 1/6 to ¼ turn more. Do not over-tighten.

 

* A nice explanation on the importance of the booster pushrod adjustment can be found here:

 

http://www.tegger.com/hondafaq/mastercylinderreplace/howworks.html

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Great write up.

 

I just finished doing the Wilwood 1 inch brake master cylinder swap as a result of the non-availability of the 70-81 280ZX brake master cylinder.

 

Note: Outlet fittings from a 79 - 81 280ZX master cylinder will also work.

 

Larger Booster: With limited space between the 240Z throttle bracket and my 7/8 Tilton clutch master cylinder I had to use a 75 280Z booster. I had to re-drill the firewall to match the 280Z booster bolt pattern and dimple the booster slightly where it touched the Tilton 7/8 clutch master cylinder. The tight space problem might not be an issue if the stock 240Z clutch master cylinder is still in place. Note: If I had used a Wilwood 7/8 clutch MC instead of the Tilton 7/8 clutch MC there would have been more space to fit the larger 280Z 2+2 10 inch booster. See kj280z post below. The Wilwood MC has a smaller footprint on the firewall.

 

Overall, the Wilwood 1 inch master cylinder and 280Z booster performs much better than 280zx master cylinder/240Z booster combination that I was using with my Modern Motorsports vented front and 240SX rear disk set up. Pedal is firm, but not hard to push using the 280Z booster.

Edited by Miles

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Awesome writeup! You mentioned "Nissan used a larger diameter brake booster on the 280ZX to reduce the pedal force of the 15/16 inch diameter master cylinder," so does the 1" master cylinder need more pedal force once paired up with the S30 booster?

 

 

Also, I believe the 73+ boosters were bigger than 70-72.. So if we have 70-72 boosters, this combo may be pretty difficult, assuming the above is correct?

Edited by spitz17

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Awesome writeup! You mentioned "Nissan used a larger diameter brake booster on the 280ZX to reduce the pedal force of the 15/16 inch diameter master cylinder," so does the 1" master cylinder need more pedal force once paired up with the S30 booster?

 

 

Also, I believe the 73+ boosters were bigger than 70-72.. So if we have 70-72 boosters, this combo may be pretty difficult, assuming the above is correct?

 

 

Yes the one inch brake master cylinder will require more force when paired up with the 240Z booster. The pedal will feel stiffer and require more effort to stop as compared to stock brakes. The fix is to go to a larger diameter brake booster such as the 280Z or, if you have space for it, the 280ZX booster. The location of clutch master cylinder limits the room available to mount the 280Z or 280ZX booster on the S30 cars.

 

I just finished installing 1 inch wilwood master cylinder and 280Z booster. Pedal feel/effort is good like you would expect power brakes to be. Car hauls down fast with minimum effort.

 

Do a search as the 1 inch Wilwood master cylinder/booster issue has been covered in the brake section. Several members have posted "how to" threads on upgrading S30 cars with larger boosters. I recall some threads dealing with booster diameter.

 

See pictures of Wilwood master cylinder and 280Z booster install on a 72 240Z.

post-178-064267800 1318637999_thumb.jpg

post-178-059660700 1318638010_thumb.jpg

post-178-078489600 1318638018_thumb.jpg

post-178-023463900 1318638029_thumb.jpg

post-178-050313700 1318640079_thumb.jpg

Edited by Miles

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Nice write up! I did this upgrade several months ago and have one minor note to add. On the brake booster, the 280z had 2 different boosters for the coupe and 2+2. My 75 280z had the original booster. I upgraded to the 10 inch 2+2 version. In addition I'm using the Wilwood 7/8 clutch master which is smaller than the Tilton which some folks are using. Everything fits great!

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I was just on Wilwood's website and saw that master cylinder and thought "hmmmm... that looks a LOT like an S30 master cylinder!" I was going to check the dimensions with a vernier tomorrow and see if it matched up but then I decided to search on Hybridz to see if anybody else had noticed it and here it is!

 

My pedal has felt rather spongy after converting the rear drums to discs from an 83 280zx, I think this 1" master cylinder would bring back the rock solid feel that my car had with the drums. I might have to put this bad boy on the top of my Christmas list...

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I did the full conversion to 280Z booster and 1" Wilwood Master Cylinder, running Wilwood Fronts and Rears.

 

The car feels MUCH better, but my head doesn't hit the steering wheel when I brake hard.

 

Am I missing something? I bled, and had the system professionally bled. Maybe a proportioning valve is required?

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I installed the Wilwood unit this weekend. I have not tested it yet. I did remove the spring and little black thing but kept the cones. It looked to me as though the cones are what seal to the taper from the flare to the master... Spitz did you say you removed the cones?

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You are correct. Keep the cones - that is what makes the seal to your flared brake lines. The black things are check valves. Remove them for disc brakes,keep them for drums. So if you have disc in front, remove that check valve. If you have drums in back, keep that one. If you have disc in front and back, remove them both. Tell us all how it works.

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Re: Removal of residual check valves from Wiwood 1 inch MC vs 280ZX MC Design. Possible conflicting instructions.

I just now removed the cones from the outlets on two 280ZX master cylinders. One of the 280ZX MCs had been on my 240Z with vented Toyota front and 240SX rear brakes for two years. The other 280ZX MC was an old one I purchased to use as a core. The 280ZX has front and rear disk brakes and yet I found residual check valves in the front and rear outlets of both 280ZX master cylinders. Wilwood says to remove the residual check valves for disk brakes and to leave them for drums. Several HybridZ threads also say to remove the residual check valves if you have rear disk brakes because leaving them in would cause the pads to drag.

 

 

 

When I installed the MM 240SX rear disk kits on my 240Z two years ago I had a 280ZX master cylinder already installed. The 280ZX MC had residual check valves in-place at the time that the 240SX kit was installed. The 240SX rear disk kits worked well with the previously installed Toyota vented front brakes and 280ZX MC. But the 280ZX MC failed and I replaced it with the Wilwood 1 inch MC in which I removed the residual check valves per Wilwood's instructions. Since the installation of the Wilwood 1 inch MC the rear brakes are weak and the pedal travel is much longer/softer than with the 280ZX MC.

 

After I installed the 240SX kit the rear brakes did not drag as a result of the residual check valves being left in the 280ZX MC.

 

So now I am considering reinstalling the check valves back into the Wilwood MC as per the 280ZX MC design. Nissan had check valves in the 280ZX MC for a for a reason.

 

Why would Nissan put residual check valves in both the front and rear outlets for the 280ZX that has front and rear disk brakes?

 

 

 

Edited by Miles

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^ I just came to post a similar question. I have one on order just as a stock replacement for now. I planned on doing the Toyota brake upgrade right away, but I don't think funds will allow for it until winter, so it will be pumping the stock front disks and rear drums on my 77. I assume it will make for a pretty stiff pedal, but I was just confirming that I should remove the front check valve and leave the rear.

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I installed a 1" Wilwood MC 2 years ago in combination with vented Toyota front calipers (S12 not S12W, same piston sizes as the solid rotor Toyota caliper but configured for vented rotors) and Maxima rear calipers and didn't remove the check valves. I've had absolutely no problems with any brakes dragging or the system being weak. I'm also running a 280Z booster (not the 280ZX) so there is a bit more pedal effort required but it helps with modulating the brakes at the limit so I prefer it this way.

 

I also took a different approach to the 10mm thread issue, I fabbed completely new lines with the 3/8" fittings on one end and 10mm fittings on the other, these connect to the splitter block/brake pressure switch mounted to the frame rail. I also eliminated the stock proportioning valve in favor of an adjustable one on the rear brake circuit, I personally think this change is manditory when replacing the rear drums with disks.

 

A couple things I ran into when I swapped to the Wilwood 1" MC.

1. One of the bleeders was completely crushed right out of the box, I replaced both of the cheap aluminum ones with the brass ones from my stock MC.

2. One of the check valves was totally mangled right out of the box. I replaced this with one from my stock MC which had 2 installed.

 

The symptom of the mangled check valve was it wouldn't let any fluid pass in either direction. I found this while trying to bleed the rear brakes and not getting any fluid at the calipers.

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I installed a 1" Wilwood MC 2 years ago in combination with vented Toyota front calipers (S12 not S12W, same piston sizes as the solid rotor Toyota caliper but configured for vented rotors) and Maxima rear calipers and didn't remove the check valves. I've had absolutely no problems with any brakes dragging or the system being weak. I'm also running a 280Z booster (not the 280ZX) so there is a bit more pedal effort required but it helps with modulating the brakes at the limit so I prefer it this way.

 

I also took a different approach to the 10mm thread issue, I fabbed completely new lines with the 3/8" fittings on one end and 10mm fittings on the other, these connect to the splitter block/brake pressure switch mounted to the frame rail. I also eliminated the stock proportioning valve in favor of an adjustable one on the rear brake circuit, I personally think this change is manditory when replacing the rear drums with disks.

 

A couple things I ran into when I swapped to the Wilwood 1" MC.

1. One of the bleeders was completely crushed right out of the box, I replaced both of the cheap aluminum ones with the brass ones from my stock MC.

2. One of the check valves was totally mangled right out of the box. I replaced this with one from my stock MC which had 2 installed.

 

The symptom of the mangled check valve was it wouldn't let any fluid pass in either direction. I found this while trying to bleed the rear brakes and not getting any fluid at the calipers.

 

 

Just to be clear, you left the check valves in the front and rear outlets?

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That is consistant with my experience with the 280ZX MC. I had no drag problems with the 280ZX MC which had check valves in the front and rear outlet ports. With the 280ZX MC the brakes were high and firm. The check valves are the only variable I haven't addressed.

 

 

Looks like the check valve issue has come up before: http://forums.hybrid...eck-valves-f-r/

Edited by Miles

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