What Master Cylinder

I have four wheel disc brakes on my nova, I am wondering what master to use,the one I have now is off of a corvette non power assist. my peddle has always been soft and I want to rectify this problem.:eek:

Four wheel disc brakes were installed on my Acadian at NNN. We didn't have enough vacuum for power assist and I didn't have a good peddle with the master cylinder provided with the brake kit. We ended up going to a local parts store and buying a rebuilt master cylinder for a 68 corvette and the brakes work fine. No power assist is needed, I have an excellent pedal and the brakes can't even be compared to the originals.

Ditto on the corvette master cylinder I think it was either a 68 or 69 non power 4 wheel disk, the pedel feels fine and stops me at 138mph. I am also using Aerospace Components brakes. Has the pedal felt like this since the cylinder was new?

I had another thaught your wheels are way up in the chassis, is the master cylinder still higher than your calipers?

I had another thaught your wheels are way up in the chassis, is the master cylinder still higher than your calipers?

The master cylinder is in the stock location, I bleed the pi**** out of them no air visible, could this be a push rod issue?:confused:

How much pedal free play do you have... should be 1/8 to a 1/16 before MC engages

How much pedal free play do you have... should be 1/8 to a 1/16 before MC engages

it feels like 1-1.5 inches

You might check and make sure they gave you a non power m/c.
I had that problem with mine.

You might check and make sure they gave you a non power m/c.
I had that problem with mine.

Did it feel real soft and almost go to the floor?

I will take a look at it this evening when I bring your Church crossmember over. Also check your E-mail if you can from work.

I will take a look at it this evening when I bring your Church crossmember over. Also check your E-mail if you can from work.

Thanks Brian, I'll see you tonight.

Joe do you know if you have the valve with the brake warning switch on your car? I did not see it but you may have put it outside the engine compartment.

Does anybody use -3 bradded line to run front to rear? I would think this would be ok but I personally have not done this so I do not know if this may cause a soft pedal. His pedal is very soft and low but does not pump up.The master is 1 inch bore but I do not know how to tell for sure if it is disc/disc or disc/drum the casting looks the same.

We crimped off the front lines and it did not make very much difference.No way to block off the rear due to the braided line,I suppose we could use an AN cap to block the line.Rear discs are GM front calipers with Wilwood style rotors and Speedway motors rear caliper brackets.

Hey guys I think you found the problem! When talking to aerospace components they mentioned using an 1 1/8 bore piston and then told me to get the corvette m. Cylinder from I can't remember 68 or 69 with 4 wheel discs and manual brakes.

Every thing I have found online says 1" bore for manual applications and 1 1/8" for power applications.It does have GM metric calipers front and rear maybe is does not move enough volume of fluid.We are going to try to plug the ports on the master and see if the pedal is hard.Then work our way from there.

Hey guys I think you found the problem! When talking to aerospace components they mentioned using an 1 1/8 bore piston and then told me to get the corvette m. Cylinder from I can't remember 68 or 69 with 4 wheel discs and manual brakes.

this is correct.

i knew his problem right from the beggining .....he needed a larger bore master to lose hydraulic mechanical advantage.this in turn creates a harder with less travel.but requires more driver effort.

the difference between a power master and non power is the bore size.

since power has assistance we can use a less mechanical advantage master with a larger 1 1/8 bore. which in turn requires less pedal travel.......

There is one other difference between the power and manual Corvette master cylinders. The manual master cylinder has a deep hole where the pushrod goes into the piston. The power master cylinder has a shallow hole that is only about 1/4" deep. This means the pushrod would have to be shortened. I would not use a shallow hole master cylinder. It can be dangerous as the pushrod could pull out of the dimple and fall out of the piston. Needless to say this would ruin your day the next time you use the brakes. I feel the 1 1/8 bore is too large and will cause high pedal effort. If all compenents are in good condition and the barkes are bled properly the system should wok fine with the 1" bore. CPP now has a even samller bore Corvette master cylinder (15/16" bore) if you need more pressure.
Tim

Joe, I have a 68 Cougar with 4 wheel disc's non power also. I put on a Wilwood 1 1/8 or 1 1/16 master and the pedal is solid, has very little travel, but needs alot of effort to stop the car. I was sure that I need to get the 1" bore MC to help this situation. I believe this is your problem also.

Joe, I have a 68 Cougar with 4 wheel disc's non power also. I put on a Wilwood 1 1/8 or 1 1/16 master and the pedal is solid, has very little travel, but needs alot of effort to stop the car. I was sure that I need to get the 1" bore MC to help this situation. I believe this is your problem also.

Wow 9 seconds, last I heard you were in the mid 10's, any way my problem is a soft and spongy peddle, I isolated the rears last night and the peddle felt normal,, so it looks like a problem with the rear brakes or maybe the -3 Teflon braided line I have running the lenghth of the car to the rear brakes?:confused:

could be... the long line... frm the MC to the tee if its all braided....

The small the bore the higher the pressure... car weight plays a big roll in MC bore selection... ... if you car is 3000 or less you can get away with a 7/8 bore...

see ya.

Wow 9 seconds, last I heard you were in the mid 10's, any way my problem is a soft and spongy peddle, I isolated the rears last night and the peddle felt normal,, so it looks like a problem with the rear brakes or maybe the -3 Teflon braided line I have running the lenghth of the car to the rear brakes?:confused:

huh? i didnt read that part...... are you getting rid of that line? going to hard line?

The flexible line you have running to the rear is the problem. All flexible lines need to be kept as short as possible. Replace it with hard line and your brakes will be fine.
Tim

I new this all a long, but was hoping it was something else, I did notice something last night my rear brake pads are loose when no pressure is applied unlike the fronts which are tight the way they should be.

Joe do you know if you have the valve with the brake warning switch on your car? I did not see it but you may have put it outside the engine compartment.

Does anybody use -3 bradded line to run front to rear? I would think this would be ok but I personally have not done this so I do not know if this may cause a soft pedal. His pedal is very soft and low but does not pump up.The master is 1 inch bore but I do not know how to tell for sure if it is disc/disc or disc/drum the casting looks the same.

We crimped off the front lines and it did not make very much difference.No way to block off the rear due to the braided line,I suppose we could use an AN cap to block the line.Rear discs are GM front calipers with Wilwood style rotors and Speedway motors rear caliper brackets.

7 months worth of tring to get that same deal to work and it will not. I sent it back to speedway and they gave me a FULL refund. I now have wilwood on the rear and GM Front. I have the same issue your having with a soft pedal. Buy the 1 inch bore master. No more then 18 inches of braided line. Trust me I spent $120.00 on lines I can not use. Wilwood will tell you the same if you call.

I have 3/16 line to the back (Steel line) and it help the pedal with the 1 1/8 bore master. The problem with this set up is the corvette calipers are very large and require the 1 1/8 bore. The new stuff and the smaller GM stuff will not work with it. Again trust me I know. The 1 1/8 is for power brakes with these calipers. How do I know... we have a second car with that set up and they work great.

I am waiting on Wilwood to send me the 1 inch bore master and not the 7/8 they told me to buy and does not work as well. To small...

Thanks for the info I will bend up some new line and go from there.

Joe,

I used -3 on the black car with a corvette 4-wheel disc master cylinder. I had hard line except for the flex to the front calipers, and a rear body to rear end line. Brakes worked great!! Not that you could tell now:(