Bore of stock master cylinder

dysan

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I'm thinking about doing a manual brake conversion but before I can decide on what new manual cylinder to get I need to know the bore size of the stock master cylinder.

Anyone know?


Thanks.
 

07gt6816

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jpc sells a kit from Race Craft, it uses a mopar style 1.125 bore master. $200 for the complete setup
 

dysan

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I know about the kit and after finding out what the stock master cylinder size is, the one from JPC has too big a bore for a manual brake in our cars from what I've been told. My friend who has his own shop and owns 2 dragsters advised me that to use a manual brake you should have a master cylinder that is smaller by at least 1/8". I don't understand why but it's something to do with the ratio between the caliper pistons and the master cylinder.

My friend Art (ArtQ on here) measured his and it is 1.057" so the one that JPC & Strange sell is actually larger than the stock one in our cars. That explains why some people have had braking problems when switching over to that kit. I need to see if Strange has a master cylinder that is 7/8" and I should be good.

I just looked on Strange Engineering's website and here's what they say...

"The Strange dual inline master cylinder is ideal for sportsman classes requiring four wheel braking. Assuming the rear wheels are equipped with 4-piston calipers; the 1.032" bore master cylinder should be used if 2-piston or single piston calipers are used for the front 2 wheels. The 1.125" bore master cylinder will allow for optimum volume and pressure for vehicles using 4-piston calipers for the front two wheels"

So...unless you have 4-piston calipers, the 1.125" bore master cylinder is too big to work correctly.
 
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gil_t2

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I am not 100% positive, but it seems that all the kits are made by the same company, They all use the 1.125 MC. on all years. Only difference i see is the adapter plates. Of all the company's selling these , Race craft is the only one to declare that you need the 4 piston calipers for proper function. I bought the unit from JPC and it works, but it does take too much effort. I am going to reinstall the stock MC if it fits the adapter plate, w/o the booster just to see how it works.
 

dysan

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I am just going off what my friend advised me and it makes sense after reading what strange has on their site. I may just piece it together getting the smaller master cylinder that strange sells and the adapter plate from race craft. I'm going to call race craft to see if they can get the smaller master cylinder from strange and sell it as part of the kit.
 

dysan

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I guess I need to find out how they mount. I'd like to use the available adapter plate so I might need to get a mopar style one since that's what the adapter plate is for.

Thanks for the info though!
 

gil_t2

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I pulled my stock MC apart today, it measures 1.062, i did not write it down it may have been 1.032, it was definitely one of the two just can't remember. Getting old is a MF.
 
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dysan

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Heh....thanks for checking yours...right in line with Art's measurement of 1.057. I didn't get around to calling race craft today to ask if they can sell the 1.032 one.
 

gil_t2

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BTW does any one know the thread size and line size , where the lines connect to the MC? I think the line is 5/16 .
 

gil_t2

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I doubled checked the bore measurment today, it is 1.062, used my new inside mic.
 

dysan

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I ordered the kit through racecraft earlier today and I'm getting it with the smaller 1.032" bore. They said they have been thinking of switching over to that master cylinder in the standard kit and they would like me to report back to let them know how it works. Won't ship out till later next week since they have to get some of those master cylinder from Strange. I'm sure it will be a little bit till I can put it in since I also want to delete the ABS module while I'm at it so some lines will need to be made.
 

ArtQ

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