brake master cylinders (510 & 240/60/80Z

Tech tips and how to's

Moderators: notoptoy, garth, S Allen

onsight512
Site Supporter
Posts: 263
Joined: Fri Mar 02, 2018 9:39 pm
Location: in the Verdugos
Model: 1500/1600
Year: High Windshield-68-70

brake master cylinders (510 & 240/60/80Z

Post by onsight512 »

Could someone educate me, possible with pics, of the differences between a stock Roadster brake master cylinder and ones from a 510 and a 240/60/80Z? My car currently has the stock master and is about to get an upgrade.

Am I correct that the stock master is 3/4"? Some were 13/16"?
The 510 is 3/4".
The 240/60/80Z is 7/8?

Could someone who has swapped in one from a 240/60/80Z explain to me (ELI5) what modifications/accommodations had to be made for that swap? Pics?

My car has Spriso's 300ZX front brake conversion and a rear from an RX-7 (rear disc). It stops well enough right now, but the pedal is softer than I like and travels farther than I like. It makes it difficult to heel/toe.
roadsterred
Roadster Nut
Posts: 36
Joined: Sat Mar 26, 2011 10:35 pm
Location: Honolulu, Hawaii

Re: brake master cylinders (510 & 240/60/80Z

Post by roadsterred »

My 68 Roadster was equipped with a 3/4" master cylinder. I replaced it with a 510 3/4" master cylinder. The only modification required was installing two brass connectors/adapters between the master cylinder and the original brake lines. I bought the connectors from a NAPA store where they were readily available.

The front and rear brakes are original discs and drums.
todd lorber
Roadster Fanatic
Posts: 363
Joined: Sun Dec 09, 2007 5:58 pm
Location: Los Angeles

Re: brake master cylinders (510 & 240/60/80Z

Post by todd lorber »

The softness is probably due to air in the line. A larger bore won't help with that, but it may reduce pedal travel.
I believe my Z had a 7/8", and I changed it to 15/16". I can't say I noticed much difference in the travel. However, the Z has vacuum assist, so the brake pedal is a bit more vague than the roadster.

You might ask Karps if they can overbore the stock master to a larger diameter while resleeving. Of course you'd need a larger piston as well, but when you look at the price that some charge for new roadster MC's, the cost may be less than buying a new master.
User avatar
spl310
Roadster Guru
Posts: 12155
Joined: Sun Dec 29, 2002 10:38 pm
Location: In front of this keyboard... in Jacksonville, Florida!

Re: brake master cylinders (510 & 240/60/80Z

Post by spl310 »

Brian Zana/Sin City Datsun has new aftermarket master cylinders at a very attractive price.
"Wow, a Roadster!" Stuart Little

1967.5 2000
1967.5 2000
1964 1500
1964 1500
1967.5 1600
1968 chassis
2000 Durango
1995 F350 Powerstroke!
More...
User avatar
theunz
Roadster Nut-Site Supporter
Posts: 1818
Joined: Sat May 02, 2009 1:54 pm
Location: Catoosa Ok.
Model: 2000
Year: High Windshield-68-70

Re: brake master cylinders (510 & 240/60/80Z

Post by theunz »

If you increase the size of the master cylinder then you will have to exert more pressure on the pedal for the same amount of stopping power. Since you have changed brakes at both ends the stock master may not be sized correctly. I would check with Spriso for their advice since they engineered the swap.
Mike M

Old enough to know better, too old to remember why!


1969 2000 solex mine since 1972, under resurrection. (Finally resurrected as of spring 2019!) 1969 Porsche 911s -worth more, but not as valuable!
onsight512
Site Supporter
Posts: 263
Joined: Fri Mar 02, 2018 9:39 pm
Location: in the Verdugos
Model: 1500/1600
Year: High Windshield-68-70

Re: brake master cylinders (510 & 240/60/80Z

Post by onsight512 »

theunz wrote: Tue Jan 12, 2021 2:18 pm If you increase the size of the master cylinder then you will have to exert more pressure on the pedal for the same amount of stopping power. Since you have changed brakes at both ends the stock master may not be sized correctly. I would check with Spriso for their advice since they engineered the swap.
Yes, Michael has said he recommends a 7/8" master for my setup. I know one from a 240/60/80Z doesn't quite 'just drop in' and so I am trying to get a solid idea of just what is involved with that swap. Something about a washer to change travel and a different rod?
User avatar
dynaguy
Roadster Fanatic-Site Supporter
Posts: 1034
Joined: Wed Jan 01, 2003 3:27 pm
Location: Colton, Wa

Re: brake master cylinders (510 & 240/60/80Z

Post by dynaguy »

As I remember, I used the 7/8" Z master. Took an adjustable rod from a spare Roadster Clutch Master. Be sure the end of the rod is the same profile as the receiver cup on the piston of the Z master. Then "machined" a bevel on 1/4" x 1"" fender washer after "machining" the O.D. down to fit the 7/8" bore. The machining was done in my cordless drill with a file. I then assembled the unit and adjusted the length of the rod to compare with my stock 3/4" master. Hope the pics help.
Pat
You do not have the required permissions to view the files attached to this post.
onsight512
Site Supporter
Posts: 263
Joined: Fri Mar 02, 2018 9:39 pm
Location: in the Verdugos
Model: 1500/1600
Year: High Windshield-68-70

Re: brake master cylinders (510 & 240/60/80Z

Post by onsight512 »

dynaguy wrote: Tue Jan 12, 2021 5:24 pm As I remember, I used the 7/8" Z master. Took an adjustable rod from a spare Roadster Clutch Master. Be sure the end of the rod is the same profile as the receiver cup on the piston of the Z master. Then "machined" a bevel on 1/4" x 1"" fender washer after "machining" the O.D. down to fit the 7/8" bore. The machining was done in my cordless drill with a file. I then assembled the unit and adjusted the length of the rod to compare with my stock 3/4" master. Hope the pics help.
Pat
Pat, thank you very much.
Please pardon my ignorance, but is the machined washer 'inside' the rubber gasket in the photos? The 'washer' is on the inside end of the clevis rod and is what is pushing down thru the bore?
User avatar
Gregs672000
Roadster Fanatic-Site Supporter
Posts: 7222
Joined: Fri Aug 07, 2009 11:47 pm
Location: Tacoma, WA

Re: brake master cylinders (510 & 240/60/80Z

Post by Gregs672000 »

I have what i recall is a band new 7/8 master without reservoirs available, as I had considered going to the larger master given my brake mods but decided to not make the change. If you're interested I'll sell it for less than the best price on rockauto for the equivalent master plus shipping as it's of no use to me. Let me know, I can send pics.
Greg Burrows
'67 2000 #588
Tacoma, WA
User avatar
dynaguy
Roadster Fanatic-Site Supporter
Posts: 1034
Joined: Wed Jan 01, 2003 3:27 pm
Location: Colton, Wa

Re: brake master cylinders (510 & 240/60/80Z

Post by dynaguy »

onsight512 wrote: Tue Jan 12, 2021 5:57 pm
dynaguy wrote: Tue Jan 12, 2021 5:24 pm As I remember, I used the 7/8" Z master. Took an adjustable rod from a spare Roadster Clutch Master. Be sure the end of the rod is the same profile as the receiver cup on the piston of the Z master. Then "machined" a bevel on 1/4" x 1"" fender washer after "machining" the O.D. down to fit the 7/8" bore. The machining was done in my cordless drill with a file. I then assembled the unit and adjusted the length of the rod to compare with my stock 3/4" master. Hope the pics help.
Pat
Pat, thank you very much.
Please pardon my ignorance, but is the machined washer 'inside' the rubber gasket in the photos? The 'washer' is on the inside end of the clevis rod and is what is pushing down thru the bore?
Unscrew the yoke off the rod, slide the washer, beveled side down, onto the rod. This will mate to the bevel in the master bore. The washer will stop at the "mushroomed" end of the rod that matches up to the cup on the master piston. There is a cir-clip that goes into a groove in the housing that holds everything together. Slide the rubber boot over the rod, re-install the yoke, adjust for length using locking nut. You're good to go.

Pat
onsight512
Site Supporter
Posts: 263
Joined: Fri Mar 02, 2018 9:39 pm
Location: in the Verdugos
Model: 1500/1600
Year: High Windshield-68-70

Re: brake master cylinders (510 & 240/60/80Z

Post by onsight512 »

dynaguy wrote: Wed Jan 13, 2021 11:46 am
onsight512 wrote: Tue Jan 12, 2021 5:57 pm
dynaguy wrote: Tue Jan 12, 2021 5:24 pm As I remember, I used the 7/8" Z master. Took an adjustable rod from a spare Roadster Clutch Master. Be sure the end of the rod is the same profile as the receiver cup on the piston of the Z master. Then "machined" a bevel on 1/4" x 1"" fender washer after "machining" the O.D. down to fit the 7/8" bore. The machining was done in my cordless drill with a file. I then assembled the unit and adjusted the length of the rod to compare with my stock 3/4" master. Hope the pics help.
Pat
Pat, thank you very much.
Please pardon my ignorance, but is the machined washer 'inside' the rubber gasket in the photos? The 'washer' is on the inside end of the clevis rod and is what is pushing down thru the bore?
Unscrew the yoke off the rod, slide the washer, beveled side down, onto the rod. This will mate to the bevel in the master bore. The washer will stop at the "mushroomed" end of the rod that matches up to the cup on the master piston. There is a cir-clip that goes into a groove in the housing that holds everything together. Slide the rubber boot over the rod, re-install the yoke, adjust for length using locking nut. You're good to go.

Pat
Thanks Pat!