Engine timing and braking problem

Which booster and master cylinder was installed with the front disc conversion?

 

I also would suspect that an icorrect Master Cylinder, propotioning valve, or rod being the issue, or a combination of 2 or more. If the peddle has exessive travel it would lead me to think that a manual brake master cylinder was used, anouther possibility could be the wrong proportining valve, the GM 67-69 disc brake systems used the same master cylinder as the drum brake cars, they just added a delay valve to the rear drums. That let the front brakes operate slighty faster than the rears preventing rear wheel lock up. You can see the delay valve up by the Master cylinder of this 67 Chevelle in this picture. What looks like a propotioning valve below is just a distribution block with the warning light switch.

The 71 and later systems use different Master cylinders for disc or drum brakes, and a proper proportioning valve. The one pictured below is not stock, but the valve is the same, and is usually mounted on the inner frame rail below the master cylinder, and combines the distribution block, and the warning light switch into the proportioning valve.

I would double check the P/N's of Master Cylinder and Proportioning valve (and Type of Valve)
I can see the timing if off severly could be affecting the brakes some, but not what you are desribing. Also I would put the car up on jack stands, and have some one operate the brakes and see if the rear brakes seem to operate differently than the front brakes.
Like when the peddle reaches the "loaded" position. It is possible that your front brakes are not working well, and with only the rear drums working I could see the conditions you describe. Hard pedal and brakes not fully effective.
Also does it happen only when the car is warm? Maybee the brakeline roughting is bad, and it's running toclose to the exaust and boiling the fluid?
Many possibilites.

 

I haven't lost brakes, but can tell you losing steering is scary as heck. http://www.stationwagonforums.com/forums/showthread.php?t=28283&highlight=butt+pucker

 

I call that pucker factor a -27. Only you and your laundryman knew how scared you were....

I've lost brake boost and steering boost when the engine stalled, but I've never had a catastrophic failure like you guys had. The closest was a broken tilt column, but the steering shaft remained connected.

 

I wish I had known that the car had a bigger cam in it prior to me starting this thread. My mechanic finally figured that out after exhausting all other possible causes. He said that it was only providing 10Hg of vacuum before he timed the car and now it's getting 15Hg of vacuum. I called the guy who built/ restored the car and sure enough he put a bigger cam in it.

Here's some back story. I bought the car from a girl who thought that it would be a good idea to have a retro wagon as her daily driver for her and her two kids. She figured out that she didn't have the where-with-all to keep it running good. She bought the car in October and I bought it a month ago. She said that she would get me the guys phone number that re-built the car but I didn't get that phone number until about a week later. I called the guy when I got his number but he didn't tell me about the cam.

So, when I bought the car I immediately took it to my mechanic who had it for three weeks. After my mechanic told me about the cam (only a week ago) I called the guy back that re-built the car and he confirmed the bigger cam.

I've tested every part of the braking system and the only problem appears to be low vacuum. So I have a few options. I can live with it, go to manual brakes, install an electric vacuum pump or install a hydroboost master cylinder (Hydroboost is a little pricey for me).

I like the idea of manual brakes but I am going to live with it for now until I have the money to fix it.

The brakes still don't feel perfect but they are a hell of a lot better than they used to be. Before I could stand on my brakes and only roll to a stop. Now I can lock em up. I was cut off in traffic two days ago and had to lock em up and they did just that. So, for now, I can drive the car.

Cammerjeff has some good points. I am going to make sure that I have the correct master cylinder, power booster and proportioning valve on the car. Then I am going to put it on jack stands and test it. I do know that the proportioning valve that is on it is the original one. My mechanic rebuilt the proportioning valve (put new seals in it and made sure that it was working right) but I still need to verify that it is indeed going to work with front disc brakes. I may need a delay valve because when I locked up my brakes the other day the ass end started to come around on me. So the rear is probably locking up before the front does. This weekend I will look at the P/N's for those parts. Thanks for the pics Cammerjeff. They are very helpful.

I like the idea of an electric vacuum pump like the one SSBC makes but everyone says that they are really loud. My car is pretty loud anyways because it has a chambered exhaust manifold, flow master mufflers and a bigger cam so I might not notice the SSBC pump.

Also, would a longer push rod that goes from the brake pedal to the master cylinder reduce the pedal travel? I've read that the push rod that comes with the conversion kits is usually too short. Can you buy an original push rod? I've looked on-line without success.

I don't know. I am gonna continue learning and figure what I am gonna do as I learn more.

I've never had a Cutlass before so I am doing a lot of learning right now.

I can imagine that loosing your brakes would be scary as hell. Loosing steering would be scary too. My buddy had his gas pedal stick open the other day. He has a newer mustang. We figured out that it was just the floor mat that got in the way.

 

I'll post some pics of the car later this week.

 

Try bleeding them out again.

 

Agreed. And if it was a manual brake car the rod at the pedal arm needs to be moved up into a new hole. I forgot how much. Like around 1/2". Many conversion kit companies have this information.

 

Here are some pics.

 

More pics.

 

More pics #2.