Engine and Transmission Tech

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jbarila
John Barilaro
Red Sox Nation!
(60 posts)

Registered:
11/02/2007 08:29AM

Main British Car:
1977 MGB Ford 302/5L

Slave Cylinder Bore Size.
Posted by: jbarila
Date: January 07, 2008 01:15PM

Will a 7/8" ID slave cylinder work with a late model MGB clutch master cylinder?
Or must it be 5/8"?


V6 Midget
Bill Young
Kansas City, MO
(1337 posts)

Registered:
10/23/2007 09:23AM

Main British Car:
'73 MG Midget V6 , '59 MGA I6 2.8 GM, 4.0 Jeep

authors avatar
Re: Slave Cylinder Bore Size.
Posted by: V6 Midget
Date: January 07, 2008 01:58PM

It will function, but I doubt if it will "work" with the stock clutch linkage. You'd have about 40% less travel with the 7/8" cylinder than with the 5/8" cylinder for the same amount of pedal travel. You need to find out how much slave travel you need to release the clutch and then calculate the bore size to give you that amount of travel when used with the MGB master cylinder. To avoid problems consider adapting the MGB slave cylinder to the donor engine/transmission if possible or use another cylinder of the same bore that might mount easier.
If you have any questions about hydraulic systems it's time to study a bit on how they work as far as how the bore size affects mechanical advantage and travel. Try [auto.howstuffworks.com] for a good basic guide.


jbarila
John Barilaro
Red Sox Nation!
(60 posts)

Registered:
11/02/2007 08:29AM

Main British Car:
1977 MGB Ford 302/5L

Re: Slave Cylinder Bore Size.
Posted by: jbarila
Date: January 08, 2008 10:35AM

Thanks Bill,
The MGB master cylinder is 19mm in diameter according to MGB/lockheed info site.
That converts to 0.75". The 7/8" cylinder converts to 0.875" The mc area is 0.44 sq. in's
and the slave is 0.60 sq. in's. 1:1.3 ratio. So for every 1" of pedal travel the slave will move 1.3" with a force .3 higher. Might make for heavy pedal feel.
JB



Edited 4 time(s). Last edit at 01/08/2008 11:09AM by jbarila.
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