FYI FORD MustangSteve's Ford Mustang Forum / Issues with master cylinder too long

**Posted by 68FSTBAK** 12/20/2018 2:46 PM

Hey guys newbie here. I purchased a 68 fastback that was not very safe to drive due to the brakes. I have big plans and have removed the old 302 and C4 trans out of the car and ordered MS T5 conversion pedal kit and booster.

I installed the pedals and clutch cable bracket and booster and at first tried to use a wilwood master cylinder 1” bore but it was hitting the shock tower. So after searching I saw it was recommended to use a 2000 mustang V6 non-traction control master cylinder. So I order one and it is still too long by about 1/2 inch. The booster that came in the MS kit is big but the instructions show that it should work. I am I missing something or do I need to modify the shock tower to clear it?

Thanks

**Posted by Bullet Bob** 12/20/2018 3:01 PM

Welcome to the forum, some of us think it's the best place on the web. I'm sure you'll get the answer here but I sure can't figure why you are having trouble. I have Steve's pedal mod and booster in our 66 with an Explorer MC (ports on the right) which I think is the same overall as the one you are using. We also installed this setup in a 64 Falcon which is tighter than the Mustang and only dimpled the tower a tiny bit.

Do you have the large 9" booster from the four cyl. Fox Mustang? That is the one that is normally used with the MS setup. I'm sure MS will chime in soon and have some ideas but until then I hope you get it figured out....seems weird.

BB

**Posted by 68FSTBAK** 12/20/2018 3:11 PM

Thanks for your response. Yes the brake line ports are on the right side of the master cylinder. The booster that came in the MS Kit is quite tall but not sure on diameter size. I thought in was a bendix but not sure.

Thanks again

**Posted by 68FSTBAK** 12/20/2018 3:35 PM

**Posted by MS** 12/20/2018 4:06 PM

The 68 boosters are thicker than the 65-66 style. It is a very tight fit with the 2000 MC. You might place a couple of washers between the firewall and booster on the bolt and stud attaching the driver side of the booster to the firewall. That will angle it over just a little bit and should then clear. OR, washers under the bottom half of the booster/firewall interface will angle the mc up slightly.

Worst case, a dent in the shock tower may be necessary. Do not hammer directly on the shock tower. I have not had to ever do this to get one to fit.

**Posted by Bolted to Floor** 12/20/2018 4:48 PM

I used the Ranger master cylinder cause I needed the ports on the other side. It and the booster both fit with just a small amount of room between the end of the MC and the shock tower. Due to the length of the MC, it would not slip over the studs onto the booster. I used a file on the back side of the MC to angle the holes. That allowed the MC to be at an angle and away from the shock tower as it slipped over the studs onto the booster. From the front, it looks normal. Sorry I don’t have a picture.

**Posted by 50vert** 12/20/2018 5:10 PM

What John said.
Also, if you shorten the studs on the booster, it helps. I didn't on mine, but I shoulda. I had to loosen the bolts holding the booster to the firewall, then tilt it sideways to get the master on.
And welcome to the best place around.

Last edited by 50vert (12/20/2018 5:23 PM)

**Posted by Bullet Bob** 12/20/2018 5:28 PM

Well that explains why I couldn't help....I know nothing about a '68.

BB

**Posted by Bolted to Floor** 12/20/2018 5:51 PM

Bullet Bob wrote:
Well that explains why I couldn't help....I know nothing about a '68.

BB

It’s not too late to learn.

**Posted by rpm** 12/20/2018 7:38 PM

Bolted to Floor wrote:
Bullet Bob wrote:
Well that explains why I couldn't help....I know nothing about a '68.

BB

It’s not too late to learn.

John, apparently you don't know BB. He's still working on fastener torque values 101.

**Posted by Hornman** 12/20/2018 10:30 PM

rpm wrote:
Bolted to Floor wrote:
Bullet Bob wrote:
Well that explains why I couldn't help....I know nothing about a '68.

BB

It’s not too late to learn.
John, apparently you don't know BB. He's still working on fastener torque values 101.

Nah, he has moved on to metalurgy. He is looking for an aluminum alloy for his A-arm adjustment wedges that will compress with the bolt torque and not crush leaving the bolts loose again.

**Posted by Bullet Bob** 12/20/2018 10:43 PM

RPM: I passed the course. Just keep pulling on them 'til they start to get loose, then back off just a bit 'til they're tight again.

Hornman: How did you know, Ron. Butt (TS&T) I think I got it. I just mixed 6061 with 10% tire weight lead and 5% cat manure. It's light weight, crushes just enough to embed the shims, and don't stink too bad after a week or two.

BB

**Posted by Ron68** 12/21/2018 8:04 PM

68FSTBAK wrote:
Hey guys newbie here. I purchased a 68 fastback that was not very safe to drive due to the brakes. I have big plans and have removed the old 302 and C4 trans out of the car and ordered MS T5 conversion pedal kit and booster.

I installed the pedals and clutch cable bracket and booster and at first tried to use a wilwood master cylinder 1” bore but it was hitting the shock tower. So after searching I saw it was recommended to use a 2000 mustang V6 non-traction control master cylinder. So I order one and it is still too long by about 1/2 inch. The booster that came in the MS kit is big but the instructions show that it should work. I am I missing something or do I need to modify the shock tower to clear it?

Thanks

I used the stock Bendix booster for a 67-68 Mustang, the same one I had used for the older p/b disc/drum setup I had and I used a 2003 V6 master cylinder. My m/c clears the shock tower by approx 1/4" with no modifications.One of your parts is not correct. My m/c looks very similar to yours.

Last edited by Ron68 (12/21/2018 8:15 PM)

**Posted by MS** 12/22/2018 7:03 PM

UNFORTUNATELY, there are several manufacturers out there making those (same specification) master cylinders. UNFORTUNATELY, some of them use varying length castings and even castings having port bosses cast into both sides, with only one side drilled and tapped for the tubes.

I have seen some of the castings that are extra long and extra wide at the front. While they fit with no problems on the 94-04 Mustangs, those who retrofit them to the early cars can have issues.

I would hate to tell anyone to grind the end of the master cylinder to fit, as there is no telling where the bore actually ends. Twelve thousand stops at 1,100 PSI may be fine, but the last (non-completed) stop when the car needed 1,103 PSI to stop may blow out the ground down bore.

So, your options are:
Angle the booster UP.
Angle the booster to the PASSENGER SIDE.
Dent the shock tower.
Install a Mustang II front end.
Try another master cylinder for same fitment, but shorter, like Ron's.
Probably ten other ways to get there, for those who are creative.

And, remember, those spacers between the booster and firewall can get bent or the firewall can get bent when tightening the booster nuts. If you tighten the nuts on the driver side tighter than the passenger side, it can cause the MC to angle towards the wider part of the shock tower, causing fitment issues. Same happens if the bottom is tightened tighter than the top. Lots of installer induced issues can crop up.

**Posted by 68FSTBAK** 12/30/2018 8:51 PM

Installed the booster and master cylinder today. Thanks to all on the suggestion. I ended up shimming out the one side of the booster to the fire wall about 1/4”.

Question though will I have an issue with the travel distance on the brake pedal due to the 1/4” shim on the one side? Any concern with the distance the master cylinder pushes in ? Thanks

**Posted by MS** 1/03/2019 9:58 AM

It might make the pedal a bit lower only way to tell is juice it up and see where it goes with full pedal pressure. Be sure you have adjusted the rear brakes first, by operating the parking brake levers repeatedly until you feel the calipers firm up.