Lets talk about Master-Cylinders

[Edbert]

That is good info there Kyle, thanks! I checked out the fox 5.0 booster in the store and it is very close to the 67 in dimensions. I purchased the thinner/wider 2.3 booster yesterday.

Well, the (neither) fox booster does NOT work out of the box with the Wilwood master cylinder, and by association will not work with the vintage MCs since the Willwood MC fit right up to the vintage booster. The pushrod on the new design protrudes too far from the mounting surface of the booster. Looks like I can try and remove the pushrod to cut it down to size or make a spacer to fit in between the two...sigh. Stuff like this is why my car is still not done.

 

[347Fastback]

I have been down this road with my 65 fastback project. I used SVO mustang master cylinder and booster with a wilwood Prop valve, this is when I was using the power booster. Now I am using just the SVO master cylinder and wilwood prop valve and factory junction block... Excellent pedal feel for manual 4 wheel disc brakes.

 

[5.0ina66]

Use an SVO MC then I don't know why you'd consider a vintage MC anyway as they're not large enough, or setup for 4xDisc applications. My 85 Continental MC (aka SVO MC) had a removable pushrod, FWIW. I know the SVO MC & Fox boosters are a tried & true combo (and cheaper than Wilwood )

For some reason, spacers just don't seem like a good idea to me, especially large ones. A picture of a cracked firewall keeps running through my mind....hanging all that mass farther off the firewall is a recipe for more leverage on the mounting points, I think. I like the idea of an adjustable pushrod much more, but thats me.

FWIW, I saw a discussion started by a guy who had Baer 13" front discs & ~11" rear, and didn't care for the looks of the Baer & Wilwood MCs, and was looking for something more factory. An SVO MC turned out to be the perfect choice for him, and Baer said any MC with a 1" or more bore would be good, so at ~1.125" bore, the SVO unit fit the bill just right. Am I biased? Naww!

HTH
--kyle

 

[347Fastback]

Yes the SVO master cylinder has worked great for me...

 

[Edbert]

Maybe I wasn't clear about which MC i am trying to use. This is the one I bought (mine is not polished though):

It is about 20% the weight of the facory MC, plus the 2.3L booster is thinner and much lighter than the 67 Bendix unit, so the weight stress on the firwall is not too much of a concern.

I cooled off a bit and went out to check again. This time I'm gonna blame Wilwood though. Their marketing says it will fit most pupular Ford Chevy and Mopar applications. While i will readilly admit a classic ustang may not exactly fit that description we are talking about a Fox booster here, and if the 5.0 Mustang does not work then what "popular" Ford application could they be referring to, maybe the mid 90s Capri or the Pinto?

Anyhow, the plunger in the Wilwood MC is near the outer edge of the MC, whereas the SVO and even the vintage MC has a big recess in them for the pushrod. I've sent an email to Wilwood tech support, we'll see what they have to say about it.

 

[Edbert]

The volume of fluid in the reservior is just short of 25 cubic inches! LOL.

Anyhow, after a 20 minute phone call Wilwood is sending me a spacer for use on Fox boosters. W000T!

 

[HHStang]

I like the Dodge truck master. They are the ones with black plastic reservoirs you see the street rod guys using. Good bore size, the stroke is great for Mustangs and works with most boosters, great looking, ports on fender side (so good for big block or modular guys) and if you get an early enough model year, you can get SAE brake lines. The newer stuff is great until you try to find the right metric to SAE adaptors or have to do metric on one end and SAE on the other end of the lines. My 2 cents...

 

[Edbert]

Do have a specific range of years for the Ram MC?

Wilwood is sending me a spacer, but if it doesn't work out I intend to use an off-the-shelf unit. Having the ports on the fender side is a big deal for aesthetic reasons alone even if my 351W has room.

 

[Hack]

I have the factory PDB front distro-block and the stock MC. UltraStang used a MkVII distro block and MC, and a 92-LX booster. I have the manual distro-valve but fear the prospect of plumbing all that when the original ones already fit. How heavilly recommended is the "upgrade"?

Great thread! I was reading through and I didn't see an answer to this question.

I think the keys for a swap are:
1. Get an adjustable proportioning valve. You need to set the rear/front balance so that the rears do not lock up first. UltraStang used the valve and IMO anyone making non-stock additions to their braking should use one. In a panic stop on the freeway it could save your life or someone else's!

2. If you are doing a custom set-up, there will be no factory distribution block that is "correct" for it. One thing about drums is they need residual pressure to keep the pads near the brake drum. So a car with factory drums will have residual pressure valves in the distribution block. IIRC, drums need about 10 psi residual and discs need about 3 psi. If you use a drum distribution block with discs, the discs will drag because of the extra residual pressure in the system. An option is to swap the residual pressure valves. The other option is to lift a distribution block from a car with 4 discs.

3. Get a MC that displaces enough fluid for your application. Several others have mentioned this. This means that if you are running 4 discs you need a MC from a car with 4 discs. Big modern discs use more fluid than vintage discs do, so a modern MC is a good idea.

4. Get the proper mechanical advantage so that you don't have excessively heavy or light pedal forces. This has also been mentioned, and it's a tough one to answer because "heavy" is relative depending on the diameter of your thigh.

I hope this clarifies things.

One other thing I should say is that bending new brake lines is surprisingly easy. If appearance is very important to you, the brake lines are also cheap so you can try again if you mess up. I can't over-emphasize this. I was really unsure about bending my own, but I was worried about nothing. I bought the pre-flared kind with fittings already on them. It worked slick!

 

[Edbert]

Great thread! I was reading through and I didn't see an answer to this question.

I think the keys for a swap are:
1. Get an adjustable proportioning valve. You need to set the rear/front balance so that the rears do not lock up first. UltraStang used the valve and IMO anyone making non-stock additions to their braking should use one. In a panic stop on the freeway it could save your life or someone else's!

I've got one, made by Wilwood. The rear lines split at the rear axle, so I plumb this in between the MC and the single line that runs to the rear.

2. If you are doing a custom set-up, there will be no factory distribution block that is "correct" for it. One thing about drums is they need residual pressure to keep the pads near the brake drum. So a car with factory drums will have residual pressure valves in the distribution block. IIRC, drums need about 10 psi residual and discs need about 3 psi. If you use a drum distribution block with discs, the discs will drag because of the extra residual pressure in the system. An option is to swap the residual pressure valves. The other option is to lift a distribution block from a car with 4 discs.

I am not using a distro-block that has any valving in it whatsoever. I have this splitting the single line from the MC to the two fronts:

I've read that the residual pressure valves for discs should be 2-pounders, but they are only necessary when the calipers are higher than the MC.

3. Get a MC that displaces enough fluid for your application. Several others have mentioned this. This means that if you are running 4 discs you need a MC from a car with 4 discs. Big modern discs use more fluid than vintage discs do, so a modern MC is a good idea.

More fluid is better, period. Helps cooling of the fluid too.

One other thing I should say is that bending new brake lines is surprisingly easy. If appearance is very important to you, the brake lines are also cheap so you can try again if you mess up. I can't over-emphasize this. I was really unsure about bending my own, but I was worried about nothing. I bought the pre-flared kind with fittings already on them. It worked slick!

I did that for the front circuit, I bought a bending tool for $14.95, made the bends smoother and they look more factory that way. Make sure you use steel tubes for a performance application. 12,000PSI is the rating on all of my componenets. I had to get the rear fitting from a California supplier, it was 9/16, which is HUGE compared to the more normal sizes.

 

[Rusty67]

I've been wondering about this. I just recently found out that my MC doesn't have a big enough bore size for my front discs and I'm going to switch to the SVO unit with the 1 1/8 inch bore. My only question is, is there such a thing as having too big of a bore size for the application or is it just the bigger the better ?

 

[jerry S]

I've been wondering about this. I just recently found out that my MC doesn't have a big enough bore size for my front discs and I'm going to switch to the SVO unit with the 1 1/8 inch bore. My only question is, is there such a thing as having too big of a bore size for the application or is it just the bigger the better ?

I have read that a bore size in excess of 1" for manual brakes will result in a hard pedal. A MC with 1 1/8" bore should be just right for 4 wheel power disk brakes.

I went with 4 wheel power disks and if I could do it all over again, I would have stayed with 4 wheel manuals but would have gone with a JMC dual MC.

 

[HHStang]

"Do have a specific range of years for the Ram MC?"

Seems like the MC's are mid 80's. I actually got mine on Eb** for $10 or something. Do a search on dodge truck master and watch for them (I didn't see any right now). They will be the ones with the black plastic reservoirs. I'll post pics and a part number over the weekend, but this mopar thread (http://www.moparaction.com/Tech/archive/disc/29.jpg) shows a picture in the meantime.

 

[caveeagle]

SVO mc part #s

Many of you have reported good results from using an SVO/ MkVII master cylendar on your 4w disk manual set-ups. I am having trouble nailing down which part # I need for this application. I don't see any manual options for an svo mc. Will the power mc work just as well? I thought the bore diameter on the power units were >1" .

I need a part # for a Manual 4W disk MC to put on my 67.

Thanks...CE

 

[Rusty67]

MC's don't change if they are power or non-power. Power or non-power means the MC is attached to a power booster of some sort.

Wagner part # F105806
AC Delco part # 18M238

 

[caveeagle]

Rusty, thanks for the part #s. do you happen to know what the bore size is for those parts?

I get that the booster is what makes the power, I just need to know how to find an SVO MC that has a small enough bore size to use on my manual set-up.

Thanks....CE

 

[CornerCarvin67]

Man... I was hoping that I could just forget about my questions on this subject. But the thread came up and now I'm hooked back into this debate. Jerry... why exactly do you feel you would have just went 4 wheel manual disks? Cuz that's where I'm at now. And I've hammered this subject over and over. Guys with the boosters say that you have to have a booster to realize the value of your disks (I have the Baer kits front and rear). I bought the car with drum brakes front and rear.... and it had a dual master cylinder in it, although I don't know if it was factory or not. Anyhow... I kept that MC in there because I didn't want to re-bend lines for use of the MC that Baer sent me with the brakes (lazy?). And yes... that little factory distribution block is still in there also. I'm a big guy... so pedal pressure doesn't really bother me.... I just want to be sure that I'm realizing the potential of my $ brakes. I recall going round with this before and we seemed to conclude that you can only put so much pressure on the disks and that the difference in manual vs. power is just a matter of pedal effort. Which leads me to believe the only real difference maker is the MC itself. I was thinking of getting rid of that factory distribution block and just plumbing in a TEE. I already have the valve plumbed in the rear for the rear brake balance. Crud... now I'm thinking too much about this one...

I have read that a bore size in excess of 1" for manual brakes will result in a hard pedal. A MC with 1 1/8" bore should be just right for 4 wheel power disk brakes.

I went with 4 wheel power disks and if I could do it all over again, I would have stayed with 4 wheel manuals but would have gone with a JMC dual MC.

 

[jerry S]

Man... I was hoping that I could just forget about my questions on this subject. But the thread came up and now I'm hooked back into this debate. Jerry... why exactly do you feel you would have just went 4 wheel manual disks? Cuz that's where I'm at now.

The cost and effort were not worth it at the end. I began with drums and moved to 4 manual wheel disks with a dual resevoir MC. I wanted my wife to be able to drive the car and not be afraid so I dropped $1g on a power conversion kit. That included an electric vacuum booster because my cam is on the hefty side and I did not have enough vacuum to operate the power brakes at low rpm. On top of the money I spent on the outlay, I paid a ton in overseas shipping because I was lied to when I placed the order in Oct. that I would have the whole kit in my possession by Thanksgiving so I could take the stuff back with me. Nope, not true, The booster did not get to me in time. I had to pay overseas shipping and duty of about $75 on top of the purchase price. Then it turns out they shipped me the wrong booster (one for a vette) and there was no possible way to get it to fit short of removing the shock towers. So I had to pay to ship it back and pay to have the replacement shippped to me (another $200 in shipping and duty). Then the electric vacuum pump turned out to be defective and does not pull enough vacuum to operate the booster. Now I have to pay to send that back and get a new one shipped to me. the costs of installing and uninstalling this stuff have been enormous. If I could do it all over again, I would just put a JMC dual MC on there and forget about it. It certainly would have been cheaper and I bet the difference betwee the dual MC and power brakes is not even noticable.

 

[CornerCarvin67]

Thanks for your time Jerry.

Hey Edbert... could you please check your PM. I want to order my Phantom gauges today and I sent a message to you to cross check the gauges I picked out. I'd like to avoid the shipping/returning nightmare like Jerry just got done discribing.

Thanks.

 

[Rusty67]

Rusty, thanks for the part #s. do you happen to know what the bore size is for those parts?

I get that the booster is what makes the power, I just need to know how to find an SVO MC that has a small enough bore size to use on my manual set-up.

Thanks....CE

1 1/8 inch