MGB Clutch master Cylinder Dimensions

[BWA]

Can someone give me the bore and stroke of a typical MGB clutch master cylinder?  The reason I would like this info is that I need to compare it to the clutch master cylinder in my 76 TR6.  I am putting a Gm 3400 V6 in my car and the clutch slave is a modified Fiero one from British Car Conversions.  British Car Conversions has done a number of these conversions in MGB's and they work well using the Fiero clutch slave with a stock MGB clutch master cylinder.
If there is a big difference between the TR6 master cylinder and the MGB one I may need to get an MGB master cylinder.
Thanks for your time and consideration!!

Cheers
Byron

[ex-tyke]

Can't supply stroke info but the bore dia of a late model 'B' clutch M/C is 3/4"

[BWA]

Graham thanks for the info.  Today I measured the bore diameter and it is 11/16".  Will the TR6 master cylinder displace enough fluid to actuate the slave or am I going to have to change to an MGB master cylinder?  If I have to go this way where is the best place to get an MGB master cylinder?  I am a member of a Triumph forum and the word is that the Moss Motors replacement master cylinder is not very good.

Cheers
Byron

[kstevusa]

Unknown Poster
I have Tilton 5/8" M/C operating my Mcleod HTOB.  I would think the 11/16 would also work. since it larger than the one I use

[ex-tyke]

Byron,
     If you decide to use the TR6 11/16" M/C, a master/slave ratio of  0.6 to 0.7 should get you in the ballpark. ie. a 1" bore slave for your application.
For comparison, from what I gather off the 'net, the production MGBGT V8 clutch master/slave bore sizes were 0.70"/1.0" respectively.

[BWA]

Thanks Graham I will have a chat with Marc at BCC, he should be able to tell me what the bore diameter of the Fiero slave is, if he can't I will pull the one off my car and measure it.

Cheers
Byron

[BWA]

After a long setback I finally got my engine running and it runs real sweet!!  Today we tried bleeding the clutch and after many attempts we could not get the clutch to actuate.  We took off the slave and came to the conclusion that the TR6 clutch master cylinder does not move enough fluid to actuate the clutch-slave.  I measured the Fiero clutch slave and it has a diameter of 27/32"
So I am thinking that I will have to get an MGB clutch master cylinder as I assume that this is what works with these 3400/3500 conversions in MGB's.  Is this going to work?
 Moss sells a Lockheed M/C for 1968-80 MGB's for $159.95, would this one be okay?

Thanks for your time and consideration.

Cheers
Byron

[mgb260]

I would just buy a 3/4" Willwood or Tilton for about 1/2 that price.

[Moderator]

There are lots of options. The cheapest I'm aware of is shown in this article: http://www.britishv8.org/MG/JamesSpradlin.htm (scroll down to the photos and captions)

[DiDueColpi]

This shouldn't be that hard to figure out guys.
It's just basic physics.
Measure the amount of clutch release lever movement that you need at the slave cyl contact point.
Measure the amount of clutch pedal travel that is available at the master cyl connection to the pedal.
Calculate the fixed parameter which is the slave in  this case.
So PI x R2 x travel required, gives you the volume needed to actuate the clutch.
The reverse is true for the master. You know the travel and the volume needed so the diameter is easy.
I would go 10% larger on the master just to give a margin for error and you're good to go......or not.....depending on the pedal position.
HTOB's are the same deal. just calculate the fluid area x the travel needed.
This doesn't address clutch pedal feel or effort though.
It just gets you adequate movement.
But the standard rule of thumb is a 6-7 to 1 ratio at the pedal.
That means that the distance from the pedal pivot to the pedal pad is 6 or 7 times more than the distance from the pivot to the master cyl. connection to the pedal.

Hope that helps some.
Cheers
Fred

[74ls1tr6]

Byron,

I'm using the stock TR6 Clutch master cylinder to clutch my T56 6 speed transmission. I think the Wilwood is the same size. I haven't had any problems yet.