master cylinder mod?

I got a disc/drum master cyl on my shelf but it's for power brakes,I need manual can I drill the piston deeper for the push rod?

 

That really doesn't sound like a good idea.
The single most important thing on any car are the brakes.
I would "bite the bullet" and get the proper master cylinder for the application that you are in need of.
Better safe!
KK

 

Agreed, the brakes on your project are not the place to do R&D. Get the right MC

 

Using a master cylinder with a deep counter bore on a custom manual system is good practice, especially if the push rod will not be retained in the bore, like most/all factory manual push rods. However, do not attempt to drill a shallow bore primary piston, because manual and power primary pistons are usually designed and configured differently. You may drill through and/or weaken the piston.
JFYI, all of the Ford power brake masters I have, use or remember working with have the deeper push rod counter bore, normally around 1 1/4" or so. The manual masters I am familiar with have the push rod retained in a shallow counter bore.

 

just use it as the trade in core for a proper manual master cylinder.

 

Master cylinders are so inexpensive these days that it's not a place to scrimp, considering what the outcome might be.

 

thanks,I'll go get the correct MC.