C3Paul

Just to clarify:

C3 Master cylinder rear reservoir (booster side) feeds rear brakes and front reservoir (radiator side) feeds front brakes

Correct?

scottyp99

Correct!


Keep the shiny side up!
Scott

Eddie 70

70 LS1, why did you use spacers with your C5 master cylinder? Is the stock pushrod too long for use with the C5 master. What is the length of your spacers and did you buy them locally or make them. So many questions!! I wonder if we could cut the stock rod to make it work. Hmmm....

Eddie 70

Took the stock master off of my vette today after originally posting in this thread back in February!! LOL!! Anyway, I wanted to see how thick the spacer was going to need to be. Looks like I might have about 1/2" adjustment left of the push rod. It appears there might be 1" or more space I need to make up. My plan to figure it out is to adjust the push rod to its shortest point and then stack washers to figure out how thick to make the spacer.

Eddie 70

An alternative to this would be to remove the pushrod and run a die up the rod and add more threads to it. I like this even better.

What does it take to add hydroboost as far as this area is concerned?

TheSkunkWorks

IMHO this is still a most excellent thread worthy of keeping open.

70 LS1

The C5 master is too tall to fit under the hood. Moving it out from the firewall and down is to clear the hood and uses the stock manual brake pushrods. Also the spacers were sized to place a slight preload on the master to ensure the rod stays centered in the shallow bore.

Eddie 70

Found out today what you mean about the master hitting the hood. It hits one of the hood latch mounting bolts. I did not think to see how much to move it forward to clear this bolt. Now the bolts for the master need to be longer if adding a spacer. Did you add longer bolts also when you did your swap?

Stock C5 master mounted in stock location.


This is where the bolt is hitting the cap if mounted in the stock location.

70 LS1

This should help you. I pulled it off my website.

I had an adapter plate machined out of 1/4" aluminum that spaces the master cylinder out from the firewall and lowers it 1". The spacers are 1" for the upper and 3/4" for the lower ones. This angles the master cylinder down slightly in order to clear the hood. The master is spaced out from the firewall to ensure a good angle for the pushrod and also for hood clearance.

This master cylinder has a shallow hole for the pushrod instead of the deep hole you would find on a typical manual master. Some people have showed concern with my design because they think the pushrod will fall out of the master if you quickly let off the pedal. I just wanted to clear that up here. The bracket was designed to place about a 1/16" preload on the master cylinder. That means there is always tension on the pushrod even with the pedal fully retracted. Also there is a lip that extends beyond the master piston so if for some reason the pedal were to pull back faster than the piston, the pushrod could not fall out of the master.

This design uses the stock manual pushrod which is non-adjustable and if I remember, the lower holes are already in the firewall, but don't quote me on that. It's been several years since I did the mod and a few years since I sold the car.

Hope this helps.

Eddie 70

I found several of the hydroboost units at a local Pick A Part and am going to go up on Thursday and see if I can get me one or two of them.

Here is a picture of my brake pushrod. It is adjustable, just not enough to use with the C5 master. I could add more threads to it but I will wait and see what happens when I get the hydroboost unit at the house.

larrywalk

If you don't want plastic or need the Wilwood name, I used this aluminum master cylinder. It has a 1" piston which is the same size as used for C2/C3 manual corvette brakes:
http://www.speedwaymotors.com/Alumin...nder,8905.html


Since I didn't want power brakes or the big vacuum booster, I bolted on a 1/8" plate on the firewall over the 4 booster studs after drilling two properly located mounting holes for the manual master cylinder, which align with the brake pedal support structure under the dash.

To be clear, the manual master cylinder mounting holes/studs are about 1" lower than the upper studs for the power brake system, and the hole for the pushrod is also lower and smaller such that the center hole in the firewall needs to be relocated. The exact distance to lower the mounting studs and center hole are determined by looking at the holes in the brake pedal support structure since they already have holes pre-drilled from the factory for manual brakes also.

The pushrod needs to be longer due to the greater depth required with the manual MC. I used a long (~6") Gr-8 3/8" NF bolt - cut off the head to approximate length; tapered the end to fit the MC piston socket, and screwed the end with a jam nut into the pedal's clevis to adjust for proper length. The new pushrod is also relocated on the brake pedal arm about 1" lower (in existing pre-drilled holes) to afford additional travel due to the smaller diameter of the MC piston.

Looks good and works great!

TheSkunkWorks

Good post on the work involved in converting to manual brakes (), but I highly suggest that anyone who wishes to do so (or those converting from manual to power) get an AIM first and to fully study both systems before diving in. The drawings you'll want to reference may not be organized together, but they're easily worth a thousand words.


Larry, do you happen to know the weight difference between that aluminum MC and the iron one?

larrywalk

I didn't weigh the MCs, but the aluminum is approximately half the weight of the cast iron MC.

TheSkunkWorks

Thanks. That sounds about right. FWIW to power brake guys, it looks like there are a couple of similar 1 1/8" bore ones available from various sources too.

slofut

Sorry to reply to an old thread but this truck master has a tall reservoir that won't clear the hood. Just tried it... LT1 hood.