Hydroboost brake conversion

[Gary Lewis]

East enough to do.  

[Blacktop]

Many thanks 😁

[Blacktop]

Great news, I managed to score a hydroboost from a '98 mustang from a friend.
It will need a new mounting plate fabricating to match the vac booster mounting holes. It will also need the actuating rod shortening to match my master cylinder. Will need to get new hoses and modify the brake pedal pin etc. But good score I think👍

[Gary Lewis]

Yes, good score!  Didn't know the Mustangs had hydroboost.

Do you need to know any dimensions?

[Blacktop]

Not at the moment Gary, thanks though.
I had a spare mc and checked its fitment, it fitted straight on! I need to flip the mounting plate 90 degrees and almost certain I'll need to redrill it or drill holes to suit in the firewall.

[Gary Lewis]

Let me know if you need measurements.  I have the hydroboost unit to hand.

[Blacktop]

Could you measure the mounting plate bolt pattern? I think on my bullnose the bolt pattern is equal but on this mustang one, there is one bolt offset.
I will measure the mounting plate I have and post them here for reference. Hopefully I can just redrill this plate and reuse it rather than have to fabricate a whole new plate.
Also, when removing the mounting nut, I managed to break it😕 so if anyone knows this thread size so I can get a new nut I would very much appreciate it. I had a quick look and it appears to be M41 x 1.6 pitch which is a weird size to me🤔

Many thanks,
Alan

[Gary Lewis]

Ok, the list of pre-work things is growing - after finishing this cuppa and having another.

I think it is:

1. Check out the '84 dealer book for grille options

2. Measure the bolt pattern on the hydroboost

3. Take a nut off Big Blue's master and booster and check sizing.  But, was it master/booster or booster/firewall?

[Gary Lewis]

Let's see if this answers the question.  Both the studs for the master cylinder/hydroboost interface and the firewall/hydroboost interface are 3/8-16.

The measurements are "raw", meaning that they may 2.400" and 3.200", but they are what I got by measuring outside/outside of the studs with my dial calipers and subtracting the measured diameter of a stud.

[Blacktop]

This is the thread size I need to source a new nut. I measure it to M41 x 1.6 pitch but I'm assuming its metric.

[Blacktop]

Apologies for the really bad image, doing this on my phone as I'm not near my pc.
This is the '98 mustang mounting plate. It is not flat and angles the booster down toward the pedal which may help it to align with the pedal pin. I may remove the bolts and weld up the holes before redrilling to the pcd to match my removed vac booster.

[Blacktop]

You can see from the side how it angles the booster down...

Sorry, the site keeps flipping some pics 90 degrees.

[Gary Lewis]

I see what you mean.  The plate on my unit is flat, with no angle.  Should be easy enough to make out of plate.

But, I don't see a good way of getting the nut off on mine.  I took off the snap ring, but don't have a socket big enough for that nut.  And my adjustable wrench can't get around the studs.

I'm assuming you tried a thread pitch gauge to discover the thread pitch.  My metric one doesn't do anything but 1/2 mm steps, so wouldn't do 1.6 mm.  However, everything on my unit that I've measured is SAE, so might that nut be?  1.6mm is really close to 16 turns/inch, which is a favourite for our nuts.

[kramttocs]

Possibly Dorman AutoGrade 1.625-16 Inch Thread Spindle Nut?

Part # 615-128 Line: DOR at O'Reillys.

[Gary Lewis]

That might be it!  I get 1.628" on the little bit of threads that protrude from the nut.

[Blacktop]

Yeah, that looks like it. I'll see if I can find one over here in the UK😟

[Blacktop]

Found one on rockauto so at least if I cannot find one here, I can at least order from there👍

[Gary Lewis]

Keep us posted.  

[Blacktop]

Thinking I will remove the bolts from the mustang mounting plate, weld on a flat plate that has the bolt pattern of my existing booster and then bolt it straight on.
Seems the simplest solution.

[Gary Lewis]

Ok, I'm as thick as two planks, but humour me.  You have the Mustang's plate off, right?  Why wouldn't you just make a new plate?

Or, maybe I'm thinking how I'd do it given the machines I have.  So, if you don't have the machinery to do that, perhaps that's why?