MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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BWA


(344 posts)

Registered:
04/13/2010 08:13PM

Main British Car:


MGB Clutch master Cylinder Dimensions
Posted by: BWA
Date: December 13, 2012 08:20PM

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
Graham Creswick
Chatham, Ontario, Canada
(1165 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

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Re: MGB Clutch master Cylinder Dimensions
Posted by: ex-tyke
Date: December 13, 2012 08:42PM

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


BWA


(344 posts)

Registered:
04/13/2010 08:13PM

Main British Car:


Re: MGB Clutch master Cylinder Dimensions
Posted by: BWA
Date: December 14, 2012 05:35PM

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
kelly stevenson
Southern Middle Tennessee
(985 posts)

Registered:
10/25/2007 09:37AM

Main British Car:
2003 Jaguar XK8 Coupe 4.2L DOHC/ VVT / 6sp. AT

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Re: MGB Clutch master Cylinder Dimensions
Posted by: kstevusa
Date: December 14, 2012 06:51PM

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
Graham Creswick
Chatham, Ontario, Canada
(1165 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: MGB Clutch master Cylinder Dimensions
Posted by: ex-tyke
Date: December 14, 2012 08:36PM

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


(344 posts)

Registered:
04/13/2010 08:13PM

Main British Car:


Re: MGB Clutch master Cylinder Dimensions
Posted by: BWA
Date: December 14, 2012 09:16PM

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


(344 posts)

Registered:
04/13/2010 08:13PM

Main British Car:


Re: MGB Clutch master Cylinder Dimensions
Posted by: BWA
Date: March 13, 2014 10:00PM

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
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: MGB Clutch master Cylinder Dimensions
Posted by: mgb260
Date: March 13, 2014 10:17PM

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


Moderator
Curtis Jacobson
Portland Oregon
(4576 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: MGB Clutch master Cylinder Dimensions
Posted by: Moderator
Date: March 13, 2014 11:10PM

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


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

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Re: MGB Clutch master Cylinder Dimensions
Posted by: DiDueColpi
Date: March 14, 2014 02:06AM

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
Calvin Grannis
Elk Grove,CA
(1151 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

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Re: MGB Clutch master Cylinder Dimensions
Posted by: 74ls1tr6
Date: March 14, 2014 09:17AM

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.


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