[buisoma]

Six months ago I put disc brakes on the front of my 68 chevelle. They seemed to work fine other than having to be careful of a a hard brake if i used then to much. I have low vacum around 8 and even with a dual diaphragm booster i can run out pretty quick. The problem I'm writing about is recently my front brakes have been getting hot after i go out for a cruise and you can smell them after backing into the garage. You notice the drag when starting off and when sitting at a light with some incline the car doesn't roll easily.
I took both front wheels off and bled any air that might be trapped in the line. I also checked if my pedal was to tight and there seemed to be adequate play there. My proportioning valve is located within 1/4 inch off of my headers, I was wondering if this could be a problem. Also if not having enough vacum could affect the release of my brakes. I know I could use a vacum pump, I just can't afford one right now. I was surprised to find that I didn't have more vacum my cam isn't that radical of a grind and there is nothing else that runs off of vacum other than my timing advance. Any help where to look next would be great.

[joe_padavano]

Boiling of the brake fluid could cause a problem. Also, did you use new rubber hoses when you installed the brakes? The liner in old hoses can collapse, acting like a one-way valve and preventing full release of the brakes.

[HalfOunce]

I second that on the hoses.... if you are worried about heat make a sheet metal shield to go between the header and valve...

[sqzbox]

I think a vacuum resivour can would be cheaper than a pump.

[T-bucket23]

If the pedal rod is a bit to long it can keep the brakes from releasing all the way or not fast enough. You also could have a mechanical bind not letting the pads release.
The hoses are also a possibility as mentioned previously.

If you put it up on a lift or on jack stands and pump the brake a few time, see if the wheels spin freely. If not crack the bleeder valve and see if they release. If so then you have a hydraulic issue. If not then it is a mechanical bind.
If it is hydraulic issue, repeat the test but crack the line at the master to see if they release. If they do either the master is bad or the rod is a bit to long. If they dont it is most likely the brake hose(s)

[buisoma]

Went out for a drive and pulled my brake pedal back with my foot after stops and the brake drag went away. Took my car home and adjusted my brake rod a little shorter and still had some mechanical drag preventing the pedal from fully releasing. I was thinking of installing a spring to pull it back all the way is this a easy fix or a bad idea.

[unix]

You should have a small amount of free play before the pedal engages the plunger that activates the booster, like but not as much as a clutch would have.

Another item, at 8 in of vacuum, if a reservoir is installed you still have 8 in of vacuum, you will need the vacuum pump. Personally I do not know how you drive it like it is, you are only asking for trouble.

[T-bucket23]

Originally Posted by buisoma

Went out for a drive and pulled my brake pedal back with my foot after stops and the brake drag went away. Took my car home and adjusted my brake rod a little shorter and still had some mechanical drag preventing the pedal from fully releasing. I was thinking of installing a spring to pull it back all the way is this a easy fix or a bad idea.

It is usually not required but if you cant resolve it an nothing is binding it probably would be ok. It could be a simple parts mismatch causing the issue

[buisoma]

Thanks for all the help you guys are great. Great forum for knowledge. Southwest Street Rods, Durango Co.