GM master cylinder bolt pattern

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Caprimaniac
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GM master cylinder bolt pattern

Post by Caprimaniac » Wed Mar 20, 2019 5:16 pm

Yeah, I'm trying to build servo/vacuum brakes into my hotrod,

Using a 7" dia single diaphragm booster, which has 3.375" bolt spacing.

It should be the "COMMON GM" bolt spacing.

So my question is: What year/ model GM master cylinders have this pattern?

Need 0.875" bore and wish for a modern aluminum body master. Will something from the 80's work, or is this common GM. stuff only on the 60's and 70's model years?
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Re: GM master cylinder bolt pattern

Post by Caprimaniac » Thu Apr 04, 2019 3:46 am

Oh- give me a hint here, fellas.

I am just a noob when it comes to US classics; had my head buried in euro- cars most of my life....
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Re: GM master cylinder bolt pattern

Post by chevyfreak » Fri Apr 05, 2019 1:40 pm

Cant say for later models but i dont think gm had a small bore master. Its usually 1" or 1 1/8. Well the 60s models that i know of used those sizes.
Must it be american? Pretty sure you would be able to find an A.T.E booster and mastercyl from a german car.


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Re: GM master cylinder bolt pattern

Post by Caprimaniac » Mon Apr 08, 2019 1:39 pm

Hi. Yes, you are right. However- a New 7" ATE booster for an Escort MK2 is something like 350$, and the 7" US/Hot Rod boosters are like 60$, so there's the reason...

I'll look aout for a 7" 2. hand ATE
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Re: GM master cylinder bolt pattern

Post by chevyfreak » Tue Apr 09, 2019 1:20 pm

I know price is sometimes to main thing when building a project.
Would have thought for you getting european parts would be easier. The ford models here , well the english bodies had girling brakes. Unless you refering to the later german bodied cosworth .

I wanted to import a 9" booster from summit for my impala with disc brakes im fitting. With exchange rates and the shipping by the time it gets here it has escalated 3 fold.

Found a booster at a friend that he says came from an opel/vauxhall model, and with luck the bolt pattern for master was the same. The pushrod that activates master was different.
The disc brake conversion also done with parts that fits and works but not for the chevy. Hubs came from opel senator. Uses same bearings just spaced further apart.
Bmw discs and calipers also from the senator. Actually stripped one for parts (i have 5 of the opel v platform cars) so had everything.
And yes, i still have the xr6 cortina if you were wondering. :D

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Re: GM master cylinder bolt pattern

Post by chevyfreak » Tue Apr 09, 2019 1:24 pm

Cant say on all the brands over there in germany but over here all the german cars opels , vw/audi, bmw and mercs runs ate brake systems.

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