Roadster Power Brakes Advice Needed

[Ol'earl]

My son and I are a couple of weeks into our build, we need guidance and I will try to put our issues down in point form:
1- Looked at Whitby kit and they advise we should buy a 1990 V8 vacuum booster locally for their kit. Is this what others have done? Is a 1990 booster smaller than a SN95 booster?
2- There is no mention of a proportioning valve in the Whitby kit. Isn't this needed?
3- We have a donor 2007 3Valve motor (orphan) and 3650 transmission and other parts including front 12.375" front brakes. Also 2017 IRS and brakes. We plan to adapt the larger front brakes to the FFR spindles.
4- The 2007 (S197) Mustang Master Cylinder is 1.0625 bore and for reasons of pedal travel I think we need to stay with this bore. The S197 booster is too big in diameter to fit even with a frame cut and the MC is not compatible with the pre 2005 boosters.
5- The 94-98 GT MCs were 1.0625 bore, however, I am not sure they would fit a 1990 booster or again is the 94-98 booster a fit with the frame cutout?
6- I would have to adapt the 2007 pedal box as the clutch is hydraulic and the accelerator is drive by wire so there is no off the shelf options here, but we think this is doable.
7- Finally any input regarding pedal travel and pedal feel with such a setup would be appreciated.

[Jeff Kleiner]

SN95 and S197 boosters are too large in diameter. Fox booster fits as Whitby advised. Yes, an SN95 master can be used with a Fox Mustang booster, just watch the booster to master plunger free travel and adjust as necessary.

Jeff

[Ol'earl]

Thanks Jeff, that is exactly answers one of my questions. Based on posts on the SVT Performance site it appears that those running Fox boosters with SN95 Cobra brakes works well, which are similar brakes to the S197. So I am beginning to think that moving to the 1" MC is ok, also it will help pedal pressure somewhat compensating for the smaller diam booster. I presume I should have an adjustable proportioning valve.

[Lidodrip]

If you are using power steering, you could also consider a hydroboost system. Mike Forte sells a complete setup including brake pedal modification.

James

[PG_Cobra]

I am currently changing my std Fox booster for the larger 93 Cobra booster (LMR new manufactured item). It installed fine in my Mk1. My frame mod clears it but is a homemade part as when I built my car (2001) Whitby hadn't released theirs, so need to check with them on clearance if you intend to use the Whitby part.

I have a disc-disc combination valve from Master Power Brakes, mostly for the shuttle valve function in the event of brake failure.

[Ol'earl]

I am currently changing my std Fox booster for the larger 93 Cobra booster (LMR new manufactured item). It installed fine in my Mk1. My frame mod clears it but is a homemade part as when I built my car (2001) Whitby hadn't released theirs, so need to check with them on clearance if you intend to use the Whitby part.

I have a disc-disc combination valve from Master Power Brakes, mostly for the shuttle valve function in the event of brake failure.

Thanks for the input. I have looked at LMR and Whitby, Whitby has the frame mod for the Fox booster, I think I will make my own mod though. The 93 Cobra booster is quite a bit bigger (8.9") vs the Fox (7.5") and I would have thought it would interfere with the steering. My S197 booster is the approx the same diameter as the 93 Cobra.
Any particular reason you are swapping out the Fox booster for the 93 Cobra?

[Ol'earl]

If you are using power steering, you could also consider a hydroboost system. Mike Forte sells a complete setup including brake pedal modification.

James
Thanks James, I have considered the hydroboost and plan to run power steering, but have not locked in yet to vacuum or hydroboost.

[Jeff Kleiner]

...The 93 Cobra booster is quite a bit bigger (8.9") vs the Fox (7.5") and I would have thought it would interfere with the steering...


It will. PG can get away with it because the steering shaft is in a different location on Mk1 and 2 than it is on Mk3 and Mk4.

Jeff

[michael everson]

Heres what I would do.
Get a 87-93 booster
https://www.amazon.com/Premium-Compatible-1984-1993-Thunderbird-Fairmont/dp/B0B4ZZ3R3K/ref=sr_1_3?crid=3JNEX7VYGBAV1&dib=eyJ2IjoiMSJ9.0GKndwB9J8mW4iXDHRaU6URlFT7q-3DQJ3z21IlKffz2FW97iUwCWsfiuOuWugxPJNHu4vv0lN3trkv DLDXZo-ARt7MIF0teKlwgAVeDACdFuNBjMzPxdh7ZD-6evRmN5XQLdxhzuej7FbCfBdO9pRw0AEIAwI7djuPfVTz9Vuv4 yXpb3FVYtMRNAELhfe1NjPy8GV2ENtOCDjVjUhXw2V65g_Meby aVQ_f8bZBRTOY.4_bB1mfExfytvMrhjDxP7KVG0n3YcwxY39Jz Q08-CN8&dib_tag=se&keywords=mustang+brake+booster&qid=1705665219&sprefix=mustang+brake+booster%2Caps%2C95&sr=8-3&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
87-93 pedal box
1995 Mustang gt master cylinder Oreilly auto part number 10-2693
Booster spacer from www.replicaparts.com
thats it for parts.
You can use a 94+ pedal box, but it requires some very minor mods. I use it all the time.
Mike

[DW66]

I did exactly what Mike recommended (Because I asked him) and my brakes are great. I think I'm using a 94 Cobra master cylinder? I did my own mod for the 3/4 tube. Everything else is easy and just bolts together. I highly recommend the replicaparts booster spacer.

Dave

[Ol'earl]

Heres what I would do.
Get a 87-93 booster
https://www.amazon.com/Premium-Compatible-1984-1993-Thunderbird-Fairmont/dp/B0B4ZZ3R3K/ref=sr_1_3?crid=3JNEX7VYGBAV1&dib=eyJ2IjoiMSJ9.0GKndwB9J8mW4iXDHRaU6URlFT7q-3DQJ3z21IlKffz2FW97iUwCWsfiuOuWugxPJNHu4vv0lN3trkv DLDXZo-ARt7MIF0teKlwgAVeDACdFuNBjMzPxdh7ZD-6evRmN5XQLdxhzuej7FbCfBdO9pRw0AEIAwI7djuPfVTz9Vuv4 yXpb3FVYtMRNAELhfe1NjPy8GV2ENtOCDjVjUhXw2V65g_Meby aVQ_f8bZBRTOY.4_bB1mfExfytvMrhjDxP7KVG0n3YcwxY39Jz Q08-CN8&dib_tag=se&keywords=mustang+brake+booster&qid=1705665219&sprefix=mustang+brake+booster%2Caps%2C95&sr=8-3&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc
87-93 pedal box
1995 Mustang gt master cylinder Oreilly auto part number 10-2693
Booster spacer from www.replicaparts.com
thats it for parts.
You can use a 94+ pedal box, but it requires some very minor mods. I use it all the time.
Mike
Thanks Mike and Dave, that's exactly what I will do and order the parts now.

[Flip Smiley]

Just a question for Mike or whoever can answer. When you install the parts Mike has listed above do you need to add an adjustable proportioning valve? I assume you need to at least gut the stock proportion block and use the new "O" ring plug to reseal. Is that adequate or does a new brake prop valve need to be added?
Thanks! Flip

[rich grsc]

Just a question for Mike or whoever can answer. When you install the parts Mike has listed above do you need to add an adjustable proportioning valve? I assume you need to at least gut the stock proportion block and use the new "O" ring plug to reseal. Is that adequate or does a new brake prop valve need to be added?
Thanks! Flip
If you have rear disc brakes, eliminate the valve completely

[michael everson]

no valve needed.
Mike

[Flip Smiley]

Thanks Rich! On the schedule for next year I am finally going to add 3 Link & 5 lug disc.
Best regards