1986 Thunderbird Prop Valve

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1986 Thunderbird Prop Valve

July 22, 2018, 12:00:55 PM

So I have swapped my rear axle to an 8.8 in the 1986 Thunderbird, and I am using the disc brakes that came on it. I gutted my prop valve and ended up stripping one of the brake lines that goes into the bottom of the prop valve. I'm having a hard to finding a new one to buy and was wondering if there is any way to replace the gutted prop valve with something else and just run an aftermarket adjustable prop valve? Any input would be great thanks. My car is an 86 Thunderbird TC.

1986 Thunderbird Prop Valve

Reply #1 – July 25, 2018, 03:25:42 PM

Replaced with some tees and couplings because the gutted prop valve wasn't really needed anymore.

1986 Thunderbird Prop Valve

Reply #2 – July 25, 2018, 08:29:32 PM

I used this on my 84.

https://www.summitracing.com/int/parts/wil-260-11179/overview/

1986 Thunderbird Prop Valve

Reply #3 – July 26, 2018, 12:16:03 AM

My brake pedal is very soft now and all, so I am guessing I need a better master cylinder. What one do I get to replace the stock 1986 Thunderbird TC master cylinder?

1986 Thunderbird Prop Valve

Reply #4 – July 27, 2018, 11:24:09 AM

for the prop,,
use a brass cut off valve in series with the line that feeds the rear.

the same product used on most refrigerators with a separate ice maker.

you can then adjust the amount of fluid flow to the rear vs front.

for the master... 93 cobra style,, but it has 3 instead of 4 fittings.

did you notice that your front driver side brake line is a home run from the master cyl while the 3 remaining wheels "pass thru" the prop valve?

1986 Thunderbird Prop Valve

Reply #5 – July 27, 2018, 08:36:51 PM

My master cylinder only has 2 fittings on it that went into the prop valve

1986 Thunderbird Prop Valve

Reply #6 – July 28, 2018, 12:13:05 PM

correct..
now what is the total number of fittings on your master?

3, correct???

1986 Thunderbird Prop Valve

Reply #7 – July 30, 2018, 09:23:21 AM

Nope, two. Two fittings that come off the master and go into the prop valve. And those are the only two on the master

1986 Thunderbird Prop Valve

Reply #8 – July 30, 2018, 06:23:14 PM

So your MC is like what was on my '83 in that it is an old school cast iron two chamber unit. It not an aluminum MC with a plastic reservoir like the 87 and up Mustangs which are three port MC's. If you just want to upgrade the MC and are okay with the current style of MC then get an '85 Lincoln Town Car unit as they have a 1" bore size (and are aluminum so they look much nicer than the cast iron units) which will work on the stock brakes on that car all the way up through the SN95 Cobra brakes (you would be advised to swap the booster to a '93 Cobra unit if you ever move up to the SN95 GT/V6 or Cobra brakes). Using the Lincoln MC will make the swap easy as it should bolt right up and the stock brake lines should work as well.

https://www.oreillyauto.com/detail/b/brakebest-brakes-4474/brake-systems-16456/brake-hydraulics-16513/brake-master-cylinder-11289/3bff094046ed/brakebest-master-cylinder-remanufactured/101518/4559060/1985/lincoln/town-car?pos=1

As for the stock brass combination valve that most people mislabel as a proportioning valve. I would use a Wilwood proportioning valve and plug kit to do this so look here and they would be the first and third items.

http://www.maximummotorsports.com/Brake-Proportioning-Valve-C145.aspx

You will need to gut the shuttle valve section of the stock combination valve which is why you need the solid plug. Then you would install the Wilwood (or like) proportioning valve inline with the rear brake line after the combination valve. With this valve installed you will need to reduce the flow to the minimum amount the valve will let flow which is turning the valve all the way out (in a Wilwood so read the installation instructions) and then back it off 3-5 full turns. Check your connections, bleed the system, driver the car normally and inspect for leaks. Now take the car out and panic brake it. You want prevent the rear tires from locking up before the front tires. If they lock up before then back the valve off a couple of turns and repeat the panic stops until you get the brake bias you need.

You can do a search on here and I think I have some pretty detailed instructions on how to gut the combination valve with pictures. I would not recommend you use anything but a quality brake proportioning valve to reduce the pressure to the rear brakes as they are designed to do this. I am not going to entertain arguments here as I do not shortcut on brakes as that is the last place anyone should look for the cheap way out. I do shop my parts but I use OEM or aftermarket brake company parts.