Hey guys, I'm new here but I've done a bunch of reading on the issues we're having and I'm hoping to get some ideas for our problem. My dad and I are building a 60 Impala, late 80's camaro 350 and T5-5spd. I've been around hot rods my entire life but this is my first build. My dad has done some restoration for over 40 years. Enough formalities... Unfortunately it seems I've come in too late to actually get good advice on what kits to buy and install, as from my research we've bought and installed the worst of both worlds. CPP drop spindles and disc brake kit in the front and the Cadillac Eldorado disc kit in the rear. Car did not have power brakes and had a single chamber MC. We've installed a booster and dual MC from a late 60's Camaro (I believe), as well as an older GM proportioning valve. The MC was bench bled prior to install and booster is mounted high on driver side of firewall. Our problem is a lack of pedal feel. The car stops fine, but the pedal travels about 8-10 inches prior to engaging. The lines were bleed rear to front probably 8 times prior to driving the car. Upon further advice we drove the car quite a bit more to let the pads set, and re-bled again yesterday. Not really any air coming from the lines so we're a bit stumped as to what we could do to get better feel. From reading around here these setups can sometimes be finicky and dependent on wheel size, tire size, etc....but I wouldn't think those things would greatly affect the lack of pedal feel? Word was we could check the proportioning valve by spinning the front tires and pressing the pedal until they stop; then holding the pedal in that same spot and going to all the tires and seeing if they would spin. That test worked, whether useful or not. We've also tried to adjust the parking break multiple times by ratcheting it out, pumping the parking brake pedal, etc. I read that the Eldorado parking brake is a pain to adjust, but the instructions are not very clear on how to do so....although they specifically say if you do not adjust properly then the pedal will go to the floor. With the parking brake set, the car will not move. There is a little bit of drag without the parking brake engaged. All signs point to no problems there, but we might be missing something. Any help and suggestions is greatly appreciative. Car is riding and driving good, but these brakes ain't the greatest feeling. Will be starting on the body work soon!
If you can and have an adjustable push rod on the pedal, lengthen it slightly to see if it helps. Half to one turn should be enough to tell if that's the issue and you can fine tune it from there.
It does have an adjustable push rod so we'll try that tonight hopefully. I read that on another thread but wasn't quite sure. Thanks!
Try adjusting the push rod you need to leave about 3/16 clearance so it does not apply pressure on the master with your foot off the peddle Is your master and Caliper matched ? What pedal set up are you using ? Some 4 wheel disc brake set up just have a shitty spongy feel. Mid to late 90’s jaguars suffered this pedal almost to the floor but brakes stopped perfectly Also some fords from the same era See if you can find out what exactly you have , front / rear Calipers / master / booster and if it’s all matched Sometimes your better off buying a complete kit Or finding a donor car and stealing the complete system. As I said about 4 wheel disc brakes, compared to a drum/drum system or disc / drum system the pedal will always feel a little softer
but the master cylinder must not be pushed in at all when the pedal is "up", it needs a little free play in the pushrod. I'd put the original drum brakes back on the rear of the car. Adding front discs is an improvement, but adding rear discs is kind of useless on a car like that, especially those old ones with the crappy caliper design.
Hi There's an adjustment rod BETWEEN the booster and the m/c that may need adjusting. Also check for the plug in the end of the m/c plunger, mine was missing even though I bought a complete booster and m/c. Also adjust the brake pedal rod until the big plunger of the booster just starts to move. I could not get a good pedal until I did that. Hope this Helps Dave
The pedal ratio has to be changed from the stock +/- 6:1 non-power to +/- 3:1 power. Some GMs had additional holes in the firewall that simply required moving the pedal box to change the ratio. There normally is not any booster input rod adjustment, other than overall length. The output rod or pin normally can be adjusted, and should have about 1/32"-1/16" max clearance to the master cylinder. This should be checked with full vacuum applied to the booster.
Thanks for the responses will look into all of the above. Calipers and MC are not matched. System is a bit hodgepodge right now. Front setup is CPP, rear is new style Cadillac Eldorado. MC and booster are 69 Camaro I believe. Prop valve is GM (all I know for now). Main lines and pedals are all stock. I debated springing for rear discs but in the end wanted the look so they're on now.
if all else seems well, linkages, levers, etc, then it sounds like you likely need a larger diam bore in the master cyl. Those large bore calipers use more fluid than small calipers or drums. You might not be supplying enough fluid on the pedal stroke. ...if all else seems ok. check master cyl diam, then look up mcs on other gm cars that use boosters, and try out one with a larger bore to get the fluid volume you need. If you had manual brakes, I would say to to watch out for pedal effort increasing with the larger bore, but with the booster, the pedal effort will still be reasonable. GM normally increases bore size considerably when comparing a nonpower brake system to a boosted system on the same car. Whatever mc size you have now, you can almost certainly be happier with trying a larger mc diam. probably WHY BE ORDINARY ?
Firewall and brake pedal already had secondary holes for the power brake upgrade. Simple as shaving the pin to fit the new hole and moving everything around. Thanks for all the suggestions guys, we have brakes and they feel good!!
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