1978 cj5 with MANUAL brakes
dodge 60 rear with drum brakes
chevy 44 front, 1/2 ton calipers

stock MC isnt pushing enough fluid, what is a good one to swap in?

thx.

are you going to stay with a manual master? Or are you concidering boost?

I think you are going to end up using the 1968 - 1969 Vette MC. There are a lot of threads on this yo can search. Most you find will be about yjs and tjs but there are a lot on cjs too.

JOSH

yeah i searched but every result was for power brakes.

stickin with manual.

To get more stopping power (line pressure) shrink the MC bore. If you have a 1" bore, use a 7/8" bore. This will up the line pressure, but lengthen the pedal travel.

Here are some P#'s I pulled off the web, they are for fords but if the mounting bolts line up there shouldn't be a prob.
When I changed my MC I had to actually get a parts manual and look up the parts myself, in my area the parts stores
have high school kids lookin crap up on a computer (nimrods).

Raybestos # MC 39037 (R.H.) (cast iron) 7/8 bore
'78-81 Ford Fairmont, Granada, Futura, Zepher (Mercury)

Raybestos # MC 39531 (R.H.) (aluminum) 21mm bore
'81-86 Ford T Bird, '82-86 Mustang, '83-86 Marquis (Mercury)

Raybestos # MC 39310 (R.H.) (cast iron) 7/8 bore
'81-83 Ford Escort, Explorer, Lynx, Mark 7 (Lincoln)

Raybestos # MC 39027 (L.H.) (cast iron) 7/8 bore (L.H.)
'76-80 GM Monza, Sky Hawk, Starfire, Sunbird


I asked a friend of mine, he said on his CJ he used a GM master cylinder from a vehicle with 4 wheel discs. He thinks it was a 79 Pontiac Firebird, and that worked for him.

weird. id think a smaller bore would move less fluid. as it is now, the pedal goes to the floor and requires a few pumps to stop the vehicle. i dont think we have room for any more pedal travel.

would a mc for 4wheel discs properly apply front discs/rear drums?

Sounds weird I know, this is from what I know from experience. But to get in writing here is a site that I ran across from google, and got those part numbers from:

http://www.chtopping.com/truck.html

QUOTED: "You may be asking yourself what will happen if I go from a one-inch diameter bore to a 7/8-inch bore? This will up the line pressure. but lengthen the pedal travel. The pedal will be firmer when the line pressure reaches the point where the brakes are being applied You won't have to apply as much pressure to stop the car "

This is the paragraph after the partnumbers on the site.



In regards to the 4 wheel disc question: This is the article my friend used from 4x4wire.com (last sentence 2nd paragraph):
http://www.4x4wire.com/jeep/tech/brakes/yjmc/


I am not a brake expert by any means. But when I did my MC swap (1/4 mile race car I was building) I asked a Brake shop owner, he said to get an MC with a smaller bore. So I grabbed a parts manual and started digging to find the mounting dimensions, RH exit, and proper brake line threads. It worked.

I do know that there are several items to watch for. Like the residual pressure valves, and the proportioning valves. The residual pressure valves hold the line pressure at a kind of preload, some MC's have them inside behind the brake line fittings, some in other places. Some systems just need beeter residual pressure valves.

Brake system info and trouble shooting
http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm


You can check out wilwood's site
http://www.wilwood.com/
Residual Pressure Valves
http://www.wilwood.com/Products/006-MasterCylinders/010-RPV/index.asp

I know its custom stuff, but they may be able to help out without purchasing a new MC.

Wilwood Engineering
4700 Calle Bolero
Camarillo, CA 93012
USA
Phone: (805) 388-1188
Fax: (805) 388-4938

Maybe if you call them they can recommend what you need.

Good Luck

I used a proportioning valve from rear drum brake 1988 Buick Regal it holds some residueal pressure and works . I have YJ dual diaphram MC , no original proportioning valve and installed variable one for the rear and quarter turn hydralic valve for brake locks front and rear which allowed me to isolate where the problem was .

weird. id think a smaller bore would move less fluid. as it is now, the pedal goes to the floor and requires a few pumps to stop the vehicle. i dont think we have room for any more pedal travel.

would a mc for 4wheel discs properly apply front discs/rear drums?

I have 4 wheel disc with 3/4 ton calipers up front and Caddy's out back. I used the Ford E350 m/c and it works great. It was also a bolt up for my Jeepster - just some adapters for the input line size.

If your brake lines input the m/c on the engine side use the Ford. If your brake lines input nearest the fender the corvette has the right orientation to not need to modify the lines at all.

The Ford has no provision for brake lights so get the NAPA SL169 brake switch and mount it to your column to make contact with the brake pedal arm.

Master cylinder out of a 80's model 2wd chevy 1 ton has no booster from the factory. Works awesome cost like $25 at autozone. I am running chevy 60 front and disc 14 rear I can lock up and slide. Beats the ol pump pedal twice and hold method.
hope this helps

that one sounds like the ticket. thanks man.

You shouldn't need to pump it a couple times with the original master cylinder. It sounds like you have air in it. The first guy was right, 68-76 corvette master cylinder. It's 1 1/18th, will fit your mounting studs and your brake lines will fit. You'll have to switch them from front to rear but that's fine. You may need to bleed those calipers off the wheels, do a search.