99VetteFRC

I need to know what clutch master bore size I should run with my stock t56 slave cylinder. I have a Wilwood 7/8 bore but the pedal is very hard. I was wondering if the 3/4 bore size would be better?

lsxRanger94

What pressure plate are you running?

74modified

The throwout needs a set volume of fluid to move the required amount. If you use a smaller bore, it will be easier to push, but will need a longer stroke to move the same amount, so check you have additional stroke available. Same goes larger bore, harder to push but a shorter stroke. Also the pedal ratio can be changed - Leverage - attaching the same master at a higher point on the pedal (changing the angle) will be easier to push as long as you still get the stroke needed.

Fry_

^^^ I'd look into the pedal ratio. The Tick clutch MC is 7/8's and doesn't create to hard of a pedal so it's likely something with your pedal ratio or clutch pedal geometry.

1981TA

iTrader: (7)

I'm using a 3/4 wilwood with mine. Shifts perfectly. Another thing to look at which will impact pedal stiffness is the angle at which the pedal rod pushes into the master. The straighter this angle, the better. If you get around 15 degrees off, I've noticed contact between the rod and the body of the master.

onetype

iTrader: (6)

I'm running a 3/4 Wilwood in the Volvo with a monster stage 3 setup. Has been flawless.

lsxRanger94

Can you post a pic of how the master cylinder is mounted and the clutch pedal assembly? Are you comparing the stiffness of the pedal to a similar vehicle with the same setup?

99VetteFRC

I don't have a pic yet... I am using a stock clutch at the moment. I bent the push rod on the master and when I took it apart to fix it the master popped out of the vice and hit the floor. The piston wedged into the bore and scared it up... ordered a new master...

markbsae

Make sure there is no side loading on the cylinder bore. That will wear it out prematurely. Move your pedal pivot to fix this. You should have a pedal ratio between 6:1 and 7:1. Measure pivot to center of foot pedal and pivot to master cylinder center line , divide the pedal distance by the master cylinder distance and that will give you pedal ratio. That's the best place to start I've built my truck pedal assembly to have a 7.1:1 ratio but im using a 13/16" bore and a stock GTO release bearing.

99VetteFRC

I put a 3/4" bore master in the car and changed the angle of the push rod and now the clutch works great!

bczee

iTrader: (12)

If you screwed up the old master and got a new one coming. Rip open the old one and measure it.