Aluminum master cylinder for 73-80 trucks

[Pyrotechnic]

I wanted to upgrade my 77 to the newer aluminum/plastic master cylinder found in 80's trucks, but I found out there were a lot of differences. One thing is the fact that it wont even fit the booster, the rear part that gets inserted into the booster is larger, meaning you need the newer booster. The other issues is the stepped bore sizes. The bore for the front brakes is larger because of the quick take up feature on the newer calipers, which means you need the newer calipers too. Too much money and work just for the master cylinder.

I searched high and low through the rock auto parts catalog, but it seems like when GM went to quick take up brakes, that's the same time they switched to the new style master cylinder. Every aluminum MC for a GM vehicle seems to be quick take up.

Today I decided to look over in the Ford and Dodge sections to see if there might be something that would fit. I found one for a Dodge D150 that has the correct bore size and correct fitting sizes. The only difference is the push rod depth - GM has a dimple to center the push rod but it looks like the Dodge push rod will seat in about 3/4 inch. There is also the port locations - the rear feeds the front and the front feeds the rear but that can be dealt with.

Assuming that the bolt spacing to bolt up the master cylinder to the booster is the same, I'm thinking that it may be possible to machine a piece of rod with a dimple in it that will fit into the Dodge MC, which will make the push rod area the same as the GM MC.

I may take a trip to OReillys to see if they will bring out both for me check if the mounting bolt pattern is the same.

Has anyone ever done this swap before? What do you guys think? The Dodge MC will be lightweight, won't rust, and has nice screw on caps for the reservoir.

Here's a pic showing both.

[INSIDIOUS '86]

Why not a aluminum aftermarket master cylinder? Lighter and better looks IMO. Think cop and wilwood and ssbc make some
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[Pyrotechnic]

Originally Posted by INSIDIOUS '86

Why not a aluminum aftermarket master cylinder? Lighter and better looks IMO. Think cop and wilwood and ssbc make some
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Cost. A new replacement master cylinder is $30. If all I have to do is make a spacer for the push rod, then all the things I don't like about the stock iron MC get solved without spending too much.

I just looked on the SSBC website and they have a really nice aluminum one, but it's $450.

[INSIDIOUS '86]

Umm... OWWWW $450 is stupid! I think the wilwood is half that too...

Well I have never had an issue with the cast iron mc but I don't like plastic... Want to race my truck on a road coarse sometime and the thought of hot fluid on Plastic... Not my idea of reliable
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[Axle]

As far as I was aware, you could not use a regular master with quick take up calipers. But you could use a quick take up master with conventional calipers.

If that is false, I'm sure somebody will chime in and set us straight, if not, you can probably stick with using the later model gm master.

Alex.

[tucsonjwt]

I had the local brake shop install a new master cylinder and they put in a Raybestos, which promptly started to rust. Next time, I am buying AC Delco like most of my parts. I only let them pick the part because they mis-diagnosed my brake problem and gave me supposedly "their cost" on the master cylinder.

[Pyrotechnic]

Insidious - I know plastic doesn't sound as good as tried and true iron, but even the ZR1 Corvette has an aluminum/plastic MC. If the GM engineers deemed it good enough for that then I'll trust it.

Axle - I thought the larger bore on a QTU MC is supposed to send a quick rush of fluid to get the pads back close to the rotor. Sounds to me like it might make for brakes that don't work the same as they did before? The main hurdle here though is that the QTU MC doesn't fit a non-QTU booster.

tusconjwt - Raybestos is a decent brand. I think the shop either didn't paint the master cylinder well, or they spilled fluid on it which ate the paint off and it caused it to rust.

Last night I took the plunge and ordered the Dodge MC. I never got to take a look at one in real life, but with the critical specs being the same I decided to take a gamble. Wish me luck!

[N2TRUX]

Several companies sell adjustable push rods if thats what needed.

[Keith Seymore]

Originally Posted by Pyrotechnic

Axle - I thought the larger bore on a QTU MC is supposed to send a quick rush of fluid to get the pads back close to the rotor. Sounds to me like it might make for brakes that don't work the same as they did before? The main hurdle here though is that the QTU MC doesn't fit a non-QTU booster.

Correct. You can mix and match non-QTU calipers and master cylinder and you will have foundation brakes - you just won't have the QTU feature (ie, reduced drag).

But - the main issue is that the QTU won't bolt up to a non-QTU booster (as you have stated).

K

BTW - the change in the calipers is a slight bevel to the square oring groove in the bore, and the dust boot is modified to create a slight amount of retraction. Those two changes add up to result in less brake drag on the rotor (from the caliper portion).

[Pyrotechnic]

N2TRUX - Some added length to the push rod is definitely what is needed. I did some searching on Google, naming it everything I could think of but I haven't been able to find one. Do you know where I could get one? It's either I get an adjustable push rod or make some kind of spacer.

Keith - That makes sense, good to know if the whole booster and MC combo is being replaced.

I got the master cylinder in the mail today! I'm very pleased with the way it looks, and it is MUCH lighter than what is on there now. The screw on caps are a nice touch as well.

Now the kicker, my flare nut wrenches aren't going to be here till next week. Can't do any work on this project till they get here.

[flamingbig10]

[Pyrotechnic]

I wish! That looks really nice!

[INSIDIOUS '86]

So if I got a wilwood master cylinder on my 86 which I assume has qtu brakes then I would prob want new calipers without the qtu? Or would they be fine and just a mushy pedal?
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[Steve Cole]

I know this thread is very old, but does anyone know if the Dodge master cylinder worked? I am looking for something similar for my '68. Thanks.

[nonstop]

I have used one on an ot car. On that one I had to slot the mounting holes to get it to bolt up, but has been working great on my car , which happens to be my daily driver.

[Pyrotechnic]

Steve Cole PM'ed me asking if I had ever finished this swap. I forgot to come back and post the results, so I'll paste here what I sent him:

The master cylinder mounting holes where it mounts to the brake booster needed to be elongated with a file to correct the hole spacing for the GM booster.

The outlet port threads are really deep and meant for a long flare nut. GM trucks have a short flare nut. You can re-flare the lines and install a long flare nut, or you can mill down the port bosses on the brake booster enough that the short flare nuts will work. I milled mine down since that was easier for me.

The the pushrod between the brake booster and MC is too short. I extended my pushrod by welding another piece of rod to it and then grinding down to the right length.

The brakes felt odd even with lots of bleeding, and then shortly after that the pedal went to the floor. I believe I had a defective MC right out of the box. I ended up just installing a stock GM cast iron MC to get it back on the road quickly and I haven't revisited the Dodge MC since then.

It should have worked though. Cylinder bore size is the same, I think I was just really unlucky and got a defective one. This isn't the first parts store MC I've bought that was bad out of the box.

I'll probably do this mod again later on. It looked really nice and was much lighter, just hope I have better luck next time.