70 Challenger Jegs Disc Brake Conversion Kit Problems HELP!

[enforcer505]

Hi Guys,

I purchased this Jegs disc brake conversion kit below:

https://www.jegs.com/i/JEGS/555/630200/10002/-1?year=1970&make=DODGE&model=CHALLENGER&submodel=BASE&engine=V8+(+5.2L+/+318+)

My 70 Challenger has manual (no booster) 4 wheel drums with stock distribution block (single big block) and 14 inch rims. brake system is all new and rebuilt.

I swapped the front brakes to this kit- but finding the brakes seem to be overheating. Ive done many of these kits in the past- Ive checked everything!

1- Caliper bolts are torqued and not holding the calipers from moving (jacked the car up and the wheels spin fine and when the pedal is pushed grab nicely and release fine also.
2- Replaced the Master cylinder to a manual disc brake type- the system is bled and no air at all in there and has a great pedal feel.
3- Calipers and pads arent dragging at all... but when rolling down the road progressively start to heat up (can feel in the pedal increased pressure and resistance and less pedal travel).
4- I purchased an adjustable rear proportioning valve for good measure and its installed. Rears were bled and no air in the system.
5- Im using the stock distribution block- Im assuming this is fine- it seems to work fine with applying and releasing the pads.

Ive replaced this kit once and Jegs sent another kit thinking there was an issue with calipers sticking but the brakes seem to heat up to much again.

Whats left is the distribution block to replace.... but whats frustrating is it doing its job fine....

Im completely lost on this and frustrated. Any guidance would be great!

 

[Xcudame]

Try using some high temperature grease where the calipers slide to reduce any friction there. Also check and verify the rotors are spinning true and not warped.

 

[enforcer505]

Try using some high temperature grease where the calipers slide to reduce any friction there. Also check and verify the rotors are spinning true and not warped.

Hey Xcudame,

upon installation i put grease on all sliding areas and the rotors are spinning true. i got my magnetic caliper out to varify. im still lost for words on this kit...

 

[Xcudame]

Well, heat is generated by friction. So something has to be dragging or rubbing, correct? If the factory distribution block is the culprit, causing the calipers to drag at speed, it's easy to by-pass. You just need a tee on the master cylinder line that will go to each front brake line. You have an adjustable portioning valve on the rear brake line, so that line can go straight to the rear from the master cylinder. All the factory distribution block does is have a piston that will slide one way or the other when either the front or rear brakes fail to work and light up a red light on the dash! But believe me, one who has experienced zero barkes, you'll know before that stupid red light lights up because the brake pedal will go to the floorboard and you'll know your in deep doodoo!

 

[enforcer505]

Well, heat is generated by friction. So something has to be dragging or rubbing, correct? If the factory distribution block is the culprit, causing the calipers to drag at speed, it's easy to by-pass. You just need a tee on the master cylinder line that will go to each front brake line. You have an adjustable portioning valve on the rear brake line, so that line can go straight to the rear from the master cylinder. All the factory distribution block does is have a piston that will slide one way or the other when either the front or rear brakes fail to work and light up a red light on the dash! But believe me, one who has experienced zero barkes, you'll know before that stupid red light lights up because the brake pedal will go to the floorboard and you'll know your in deep doodoo!

problem is im not sure whats left... proportioning valve tho seems to work... i dont want to start hacking into the stock system to bypass it. i apply the brakes they stop. release they disengage. the heat is i think in the pads... theres really nothing holding them back.. but this seems to be a very interesting problem.

 

[Chryco Psycho]

Faulty residual pressure valve maybe , usually inside the master cyl , , drum require 10 PSI , disc is 2-3 PSI , wht master are you using ?

 

[Challenger RTA]

As I was reading your problem.

Faulty residual pressure valve maybe

I did not look at the parts or instructions. Some installations require remover the residual valve. Was there anything about that?

 

[Challenger RTA]

Kind of read through it. It make no mention of what master cylinder to use.
1 A disc brake set needs a larger reservoir for the disc.
2 There was nothing about using a manual brake master cylinder.
3 where was it to use what master cylinder?

 

[Challenger RTA]

From instructions key take aways.

IF YOUR BRAKE PEDAL IS VERY SENSITIVE AND THE BRAKES GRAB

1. Your pedal ratio may be too high. Power brakes will require a 4:1 to 5:1 ratio. If your ratio is around6:1 you are getting too much mechanical advantage making the brakes extremely sensitive. Adjust the ratio to correct level

3. Too large a booster for front drum brakes. Drum brakes do not require as much pressure as disc brakes(500 psi vs. 1,000 psi). If your booster is very large (11”)

 

[Xcudame]

The issue could be your master cylinder like @Chryco Psycho and @Challenger RTA have mentioned.

 

[Bret Schneider]

Long shot but have you checked the front brake hubs/rotors for excessive run out? Wheel bearings properly adjusted? If the rotor wasn't running true between the brake pads it's possible that some friction could occur between the pads and rotors and begin to build heat. Typically you would feel some degree of pedal pulsation if this was the case but something to check anyway.

 

[MILOJ]

The rod was too long to my old car master cyl I shortened it some and no more dragging Also if you are using a drum brake master cyl on disc brakes you have to remove the residual valve in the master cyl on the line that go to the disc brakes that are added I had to get this figured out on my old Dodge WM300 and finally no more overheating front disc brakes that I added

 

[enforcer505]

Hi Guys,
Im using a disc brake master cylinder (new).

The end play or run out is fine- there is no pulsation in the pedal. I do notice the heat build it because the fluid starts to expand and starts claiming the pads.

 

[enforcer505]

Im running also manual disc fronts and drum rear. no booster used.

 

[Xcudame]

OK, here's a trick. Drain out all the DOT 3 fluid you're probably using and refile with DOT 5. You'll have to re-bleed the master cylinder and all four wheels. But DOT 5 has much better heat resistance qualities. Kinda spendy and time consuming, but at this point, worth a shot! By the way, I've been using DOT 5 in my 70 Challenger for the past 30+ years - front disc, rear drum. No brake problems.

 

[Steve340]

Is there a little free play on the master cylinder pushrod?
The master cylinder piston may not be returning all the way.

 

[Bret Schneider]

" I do notice the heat build it because the fluid starts to expand and starts claiming the pads."

That's interesting... any changes to the exhaust system lately? As in headers or a leaking exhaust pipe that could be heating up a brake line/component resulting in the brake fluid getting hot? Need to find the source of that heat and address it.

 

[Chryco Psycho]

Which line is connected where the front brakes should be closest to the pedal / firewall , the rear brake line should be farthest away from the pedal