Cure(s) for soft brake pedal needed

[180 Out]

I have put the Trans Am Racing conversion kit in my kids' '65 289 fb with factory drums and single pot MC. It does not perform up to expectations. The pedal feels soft and the brakes will not lock up.

The T/A kit consists of a dual pot MC and a small booster, both of unknown origin. The MC looks like a Ford part, with the same shape as a Ford and the same cap and with the ports facing out toward the driver's fender. The brakes themselves are the standard (i.e., not Force 10) Stainless Steel Brakes 4-piston conversion kit. Also included is an adjustable prop valve for the rear brakes.

I have heard from a pro that a smaller bore MC might help. I would do this swap if I knew what part number to ask for. Does anyone know?

One thing I have seen, while watching under the hood with an assistant pressing on the brake pedal, is that the firewall flexes enough that I can see the MC rising 1/4 - 1/2 inch. I have read on the web that a brace running from the firewall to the shocktower can correct this.

I have bench bled the MC and the lines more than once. The rear drums are properly adjusted.

I have read that there is a factory prop valve in the rear brake line. If there is, then it's still there, because I have not taken it out. I have read that a 10 lb residual pressure valve in the rear lines can help a soft pedal.

I hope the length of this post does not turn people off, because I would really like to fix this. Any input from folks with experience with the small bore MC, the firewall brace, or the residual valve fixes would be appreciated. Best of all would be someone who has dealt with this problem and beat it.

 

[LMan]

for the 67s, the residual valve is in the rear line near the axle. Do you know where the '65 valve is? It would be worth making sure it is functional.

 

[180 Out]

No, I don't know where it is, or how to test it if I knew. Right now, my plan is to put in an aftermarket 10 lb-er from Master Power Brakes, swap in a smaller bore MC (if I can get a part number) and cobble together a brace with rod ends and clevises. In other words, throw parts at it.

 

[LMan]

do you have a shop manual?

 

[Az Pete]

My 66 Coupe had bad brakes from the start. I did new drums, shoes, and cylinders on the rear. Then went to the front drums and just cleaned everything and did all the adjustments. Brakes work great now. Been good for about 2000 miles. Every once in a while, the right front tends to be a bit tighter. I think that it is just needing some new springs. I found the rebuild and flush did great.

 

[mustangdave]

I can't help but are you saying that you have a frt. wheel disc conversion from S.S. and then you did the T.A. booster conversion? This will help others understand your problem.

 

[180 Out]

LMan: yes I have the '65 shop manual.

AZ Pete: I've bled the brakes several times, and since they're only about two years old and with less than 10,000 miles, and since the soft pedal has been characteristic from the gun, I'm reluctant to rebuild the calipers. I rebuilt the rears at the same time as I did the T/A conversion.

Mustangdave: The T/A kit includes the SSBC 4-piston front disc brake conversion kit. In addition, the T/A kit includes a CNC-machined aluminum spacer and 4 studs to mount it through the firewall and into the pedal support; a small booster; a dual pot MC; and an adjustable prop valve.

I think the firewall flex, which I understand to occur with cable and hydraulic clutch conversions too, is exacerbated by the T/A kit. That is, the centerline of the booster/MC is about 1" higher than the hole in the brake pedal shaft where the booster pushrod attaches. This means that the booster pushrod runs at an ascending angle from the shat to the booster. This means that pedal movement exerts an upward force on the booster, not a solely horizontal one like it should.

Anyway, keep the responses coming!

 

[1966conv]

I've replaced the brake systems in 3 66's and have never found an inline valve of any kind. I have the distribution block up front in the fender apron and the distribution block on the alxe tube in back, but nothing in between.

 

[LMan]

I think your idea on the firewall flex is a valid one. Can you adjust matters so the pushrod works horizontally?

 

[rbohm]

part of the problem is the firewall flex. there sould have been either a reenforcing plate, or instructions on making included in the kit. also make sure the rear drums are adjusted properly, and that the brakes are properly bled, and yes firewall flex will prevent proper bleeding.