I have a 1985 Ford F-150 with a stock cast-iron master cylinder. I was wondering if I could replace the master cylinder with the see-through plastic master cylinder that started in 1987? Can I just replace the cylinder, or will I need to use a 1987 brake booster as well?

 

Was searching everything I could find about my next project when I ran across this old question by Lariat 85. I've started the process by getting a new booster (O'Reilley #54-74211) for an '85 and the MC ( O'Reilley NMC 4007) for an '87. All was going great until I couldn't find adapters to go between my existing '85 lines and the new '87 MC.
I figured out the easiest way to hook it back up with my original lines was to swap the flare nuts and grab a "proportioning pressure regulator control valve" (E7TZ2C161C) off of an '87 in the yard so that the threads match up.
My question is whether or not anyone has used this part, and if so, did you gut it or leave it fully functional.
I guess I'm worried that if left functional, it might react poorly with the stock Proportioning valve down on the frame.
What are your thoughts?

 

A little additional info;
The flare nut thread sizes on the original cast iron MC are
Primary - 9/16-18
Secondary - 7/16-24

'87 MC w/ plastic reservoir
Primary - M18-1.5
Secondary - 9/16-18

I was able to find an adapter to go from 7/16-24 to the 9/16-18, but could not find one to go from 9/16-18 to M18-1.5

What I did notice was that the "Proportioning pressure regulating control valve" that is used on the '87s has the M18-1.5 to 9/16-18 threads, so all I did was change the nuts on my existing lines.

It would seem that now I have two devices that want to regulate the primary and secondary pressures!

My concern is whether they will play nice or cause problems. I had read something a while back about gutting the valve that mounts on the MC, but not sure if I should and would like to hear some opinions.

 

After lots of reading last night, it seems that I have the answer to whether or not I should gut the "Proportioning pressure regulating control valve". Here is an excerpt from the shoptech.com website and the first rule is what did it for me;

Proportioning Modifications

We could start this section by clearly stating that you should not modify your proportioning valve. But, what fun would that be? In all seriousness, making changes to the proportioning valve to effect brake bias should be left to those with the proper tools and measurement devices, but if you have tweaked your vehicle beyond recognition, this may be your only solution to restore a sense of proper bias to your braking system.
We’ll start here with three of the most basic rules regarding proportioning valve installation and selection.
1. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed if the factory unit is still in place. Proportioning valves in series with one another can do nasty, unpredictable things!
2. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed in-line to the front brakes. The effect would be to make your vehicle rear-biased before you could say “terminal oversteer.” Front brake line pressure should always be left alone – only the rear pressures should be considered for proportioning.
3. In all cases, the basic brake system balance needs to be close to optimized to start with. This is the only way that a proportioning valve can be effectively utilized. You should never assume that simply adding a proportioning valve will address all rear-bias conditions, as even the best proportioning valves must be well-matched to the target vehicle.


So, here is a pic of the valve that I pulled off of an '87



Here it is turn apart and the exploded view from Ford



And lastley, the stock '85 proportioning valve that I'm leaving on my frame rail.


The best thing about taking the adapter apart is that the first fitting (to the far left in the second pic) is simply a bushing that goes from the M18-1.5 to the 7/16-24 that my stock line has. I won't even need all of the rest of the parts.
I still need to get this all back together and bleed everything but I think all will be golden.
Stay tuned for a road test in the next couple of days.

 

I'm curious. If you were changing the line nuts anyway, why didn't you change the primary to M18-1.5?
Or am I missing something?

 

The M18-1.5 is not a flare fitting on the male end, it's simply a threaded fitting. The female side is a flare at 9/16-18

 

Oh, you mean it's not meant to have a brake line screwed directly in to the MS? Only the valve is meant to screw in?

 

That correct. The flared end of the line goes into the valve, the valve goes into the MC.

 

Reviving this to find out how it's working for you.
I think I'm going to do the same thing to my 85.

 

Everything is working just fine for me. No leaks and stopping power is great.

 

Great! Thanks for the reply. Now on my to-do list.

 

Looks like the PN for the MC mounted proportioning valve is E7TZ-2C161-B.
In case anyone is doing the conversion and can't find a used one.

 

Turns out I didn't need the proportioning valve.
I had bought, but never look at closely, a Wagner MC120368 which came with a straight through adapter.
Both lines are 3/16" dia so I had to get different fittings, which NAPA had for about $1.50 each.
I have a 25 foot roll of copper nickel brake line (BK 6413347) and am making new lines today between the MC and stock proportioning valve.

If you're using different size lines you'll need different PN's.

 

Well, turns out it's not a simple conversion on over 8500lb trucks.
The '87 MC mounting holes are slightly too close together.
I don't know if an '87 booster will fit my '85.