More info on 78 Avanti master cylinder

[davette59]

Here is a link to photos of my master cylinder that I am having trouble matching. maybe the plunger that looks like an intake valve comes with the booster and I am assuming it comes with the MC. Is there a specific type of end that goes into the MC or does it not matter. If the size and configuration of the rod going into the end of the MC doesn't matter, then I think the one for the 67 Ford Fairlane 500 might work. here are some pictures----

http://s1213.photobucket.com/user/davette59/library/1978%20Avanti%20II%20%20master%20cylinder

[sweetolbob]

The one you show in photobucket looks like the drum brake unit.

This is the one on both my 74 and 83. It's a picture from Rock Auto of the disc brake unit 67 Galaxie

It uses the push rod you show in photobucket.

My 83 looks like your plumbing. The 74 looks like this. The front is plumbed from the other side but it makes no difference in the real world as you see here.


Bob

[davette59]

Went to the Rockauto web site and couldn't see anything showing it with the type of plunger that I have. I looked under the 67 Ford Galaxy. I feel I may be getting close but the plungers that I see have a metal loop on the end.

[sweetolbob]

Dave

Remember that your car comes with parts from every auto maker in the US and some foreign. The rod that is troubling you that sometimes comes with the M/C, the ones I bought didn't have them, would fit a Ford nicely. The problem is your booster which, I believe, is a Chrysler unit. You need to use the one you have. I have the same rod in both of my Avanti's with the Ford M/c's I posted and they stop. If you want a new rod, I'll let you search for it.

Bob

[davette59]

I think you're right, the master cylinder will work, It's just the plunger that doesn't come with it. I should be able to use the old one, I just hope the rubber is still good on it to make a tight fit.
thanks for everyone's help, I'll let you know how I make out.

[davette59]

OK, the master cylinder that is supposed to fit my car is from a 67 Ford Farilane 500 according to all the Avanti sites. So I bought one from my local FLAP store. When this came in we noticed that the larger reservoir on mine is on the opposite end ( see the pictures in my previous post ). Also. Mine has both brake line connections on the side and the new one had one on the side as well as the bleeder and the other on the bottom. I wonder if the PO found this MC somewhere and jury rigged the brake lines to fit. Shouldn't the larger reservoir be for the front disc brakes? Does the bore size make a big difference? I have been to every parts house in town and none can match my existing MC. Can I just use the one for a 67 fairlane 500 and reroute the lines to fit? I can get the new one from Studebaker Int. But I think it would simply be the same as the rebuilds in the store. Quite a mess. Help!

[sweetolbob]

I posted several pictures of the correct M/C which you have been purchasing all over town. The rear port on my M/C goes to the front discs. Do what you need to get it correct.

Bob

[Gunslinger]

Bore size does make a difference. The smaller the bore size, the harder the pedal with less travel. The bigger the bore, the softer the pedal with longer pedal travel. Unless special design needs are necessary, engineers generally work out a compromise between the two for the mass market.

[davette59]

Thanks for your help everyone. I feel a little stupid at times but it's just me being over cautious. I only want to do things once, too many times I've jumped into things only to have to do them over. The fan belt thing was really stupid once I looked more closely at it. I am going to get the right MC tomorrow, trace the brake lines out and switch them around as necessary. If the rubber end on the plunger ever goes bad it's probably time for a new booster. I will be posting some pictures of the carb and intake manifold where the PO disconnected several hoses etc. looks like most are vacuum hoses. Some of my questions may be stupid to you but it does give you something to do in your spare time. Sweet Bob, your pictures were very helpful. It's so nice to have others so willing to help.

Dave

[davette59]

Gunslinger, I measured the bore on my existing Master cylinder with a micrometer and it looked like 1.2. I am going to go with 1" on the new one. Thanks again.

[Starlight]

Davette59.....You might want to take a look at the master cylinder from a 74 thru 78 Dodge RamCharger........bolts right up and works great......I put one on a friends 64 Avanti and works great.....Just saying.......Keep on Studebakering

[rstrasser]

Gunslinger;
I believe you are wrong.
The smaller the bore size of a master cylinder; more travel is need for the same amount of fluid to be sent to the wheel cylinders. Hence more travel less foot pressure.
A larger bore requires less travel but more pressure. The piston displaces more fluid with each inch of piston travel.
There is a trade off between how much fluid is needed and how much pressure is required.
Ron

[Gunslinger]

My understanding is the smaller bore makes for a harder pedal and increased pressure. I've been told that and seen it in several sources. I know it sounds counter-intuitive but I've understood it to be that way for many years.

[davette59]

I just ordered an A1 Cardone 10-1379 master cylinder for a 1967 Ford Fairlane 500. Hope it fits but from all I understand it should. I searched all the info I could and couldn't find the bore size so I guess it's a crap shoot.
Ai looked at my starter that I think is getting heat soak because it usually starts great when cold but slow or does not start when hot. When I wait for it to cool down it's OK. I was going to put a shield on the solenoid but after looking at it, there is a shield the below and the length of the exhaust manifold and it isn't that close to the manifold. However, the exhaust head pipe coming off the manifold to the muffler is within inches of the starter itself. I am going to try wrapping a heat shield blanket around the exhaust where it is close to the starter. Maybe some foil backed insulation or some other aluminum type shield wrap.

[studegary]

Gunslinger;
I believe you are wrong.
The smaller the bore size of a master cylinder; more travel is need for the same amount of fluid to be sent to the wheel cylinders. Hence more travel less foot pressure.
A larger bore requires less travel but more pressure. The piston displaces more fluid with each inch of piston travel.
There is a trade off between how much fluid is needed and how much pressure is required.
Ron

You are correct as far the relative quantities of fluid moved (related to pedal travel), but that is not the concern with different bore sizes. The ratio of the master cylinder bore size to the slave cylinder bore size is what determines how hard the pedal has to be pushed in order to get the desired pressure at the brakes. It is the area that the pressure is applied across that matters.
In my mind this is clear, I hope that what I wrote is also clear <G>.