vipervetteguy

When I bought the car it had cheap AZ pads. I replaced them with Hawk 5.0 pads. Since that made no difference, I concluded pads were not the problem.

vipervetteguy

Car brakes very straight. No initial bite and even with massive leg pressure, it stops like old drum brakes that got wet.
I ordered a dual MC for a manual brake car. If it's the wrong bore, then the single line MC I replaced was also the wrong bore. Seems unlikely.

vipervetteguy

Bought MC for manuals. Rod is in correct hole on pedal for manual brakes.

vipervetteguy

Yes. They are true and brakes have no shudder at all.

vipervetteguy

I keep thinking about the MC, too. It's from Eckler's for a manual car. The reason I dismissed the MC bore theory is that would mean the single line MC in the car when I bought it was also wrong. I think it's time to get a gauge and check the psi at each caliper. That will give me more info to make decisions.

Nowhere Man

Look up Lone Star Calipers and talk to them and buy all your brake needs from them.

Tampa Jerry

I will weigh in again. Do you have two bleeders on the top of each rear caliper? Having a plug on the inside caliper instead of a bleeder will give you a soft pedal as air is still trapped in the caliper. Others have said, GM used this brake system from 1965 through 1982. They were used in racing applications for years. Jerry

boxster99t

FWIW, I had the exact same issue with my 67 with manual disk brakes, replaced the MC and bench bled it; flushed all the brake fluid replacing it with DOT 4 using a motive power bleeder and it was properly bled; checked the runout of the rotors; replaced the pads with organic pads. And the car never, ever, stopped anywhere as good as I thought it should (example: I could literally stand, and I mean stand up and put both feet and all my weight on the brake pedal and it would not lock up any of the brakes). The rubber brake hoses were replaced by the prior owner right before I bought the car so I didn't touch them.

After living with it that way for four years, I did the power disk brake conversion, replacing all the brake lines, new MC, booster of course, and with new calipers all around from Lone Star. Only the rotors which were original were re-used.

With all due respect to everyone who says you don't need power brakes, wish I had done the conversion day one as opposed to living with it for years. Now the car stops better than it ever did, and feel very safe driving it. I can lock them up--actually did that once one year during my state safety inspection when the inspector said, get the car up to 15 mph and hit the brakes. He remarked that most guys with old cars cannot make them stop like mine did.

When you consider that nearly every car on the road these days has power brakes and most are 4 wheel power disk brakes, especially for those who have worked on brake systems, not sure why you wouldn't want power brakes aside from spending some money--around $1200 in parts and could have been less if I didn't pay the extra for the period correct (but new) master cylinder and booster. Just my story and two cents--do the conversion. You won't regret it.

karkrafter

I added a PB Booster to my '66 couple summers ago, difference was like night and day. Didn't change on single item except add the Ecklers booster. Never loosened a brake line so never had to bleed the brakes...Still the stock single M/C [fairly new]

The single best inexpensive upgrade I have ever made to any car, bar none.

toddalin

Use a M/C with a smaller bore diameter (e.g., Wilwood).

You may also try to put 2# residual valves in both the front and rear circuits.

vipervetteguy

So you added a booster and kept the manual brake sized MC? I thought you have to change to a power brake-sized bore MC to work properly.

GTOguy

A 4 wheel brake system that will not lock up the wheels, disc or drum, is one that is not operating as designed. You have a pressure problem, most likely, or a delivery problem. Both hydraulic in nature, and possibly caused by the wrong master, a defective master, defective binding calipers, decayed flex hose, etc. Borrow a brake pressure gauge and check the line pressure at each caliper. That will get you going in the right direction. Your car should be able to stop on a dime.

emccomas

Does seem unlikely, but not impossible.

Check the actual bore size, or get the part number of the MC and get the specs on it, then compare it to what should be on the car.

LB66383

Interesting. I also have a '66 non-power brake car. I converted to a '67 dual master several years ago. Recently converted to O-ring calipers (rebuilt the existing lip seal calipers, didn't get new ones). The rotors are the ones that came with the car when I got it. I do have stainless braided flex lines. Yes, because it's non-power it takes more pedal effort, but I've always felt that the brakes were more than adequate. I've locked up a couple of tires momentarily on rare occasions dealing with stupid drivers. I've never just taken it out to test it by just standing on the brakes, but I see no reason why it wouldn't lock up all four without having to stand on the pedal with both feet. I don't know the bore diameter of the master, it came with a conversion kit I bought from a major supplier.

emccomas

OK, some data to work with

1965-1966 Corvette manual brake master cylinder - single line
GM Part # - 3866446, Casting # - 2225032 - 1 inch bore

Mid 1965-1966 Corvette Power brake master cylinder - dual line
GM Part # - 5467005, Casting # - 5467084 - 1 inch bore

1967 Corvette power and non power master cylinder- dual line
GM Part # - 5458831, Casting # - 5455509 - 1 inch bore

1968-1972 Corvette manual master cylinder - dual line
GM Part # - 5458831, Casting # - 5455509 - 1 inch bore

1968-1972 Corvette power master cylinder - dual line
GM Part # - 5461184, Casting # - 5460346 - 1 1/8 inch bore

1973- early 1974 Corvette power master cylinder - dual line
GM Part # - 5461184, Casting # - 5460346 - 1 1/8 inch bore

1973- early 1974 Corvette manual master cylinder - dual line
GM Part # - 5458831, Casting # - 5455509 - 1 inch bore

1974 late - 1976 Corvette power master cylinder - dual line
GM Part # - 5461184, Casting # - 5460346 - 1 1/8 inch bore

1974 late - 1976 Corvette manual master cylinder - dual line
GM Part # - 5455509, Casting # - 5455509 - 1 inch bore

Which of these is on your car now?

MikeM

For a couple of reasons, I don't think you have a problem with the bore size in your MC.

I suspect you are just not pushing on the brake pedal. Have you thought about filling your pants pockets with wheels weights and trying the brakes out again?

But I would do a pressure check, just to cover the bases.

vipervetteguy

Eckler's # 25-121868-1 has a 1" bore.

rene-paul

I have a question; Is it physically possible to install the rear calipers on the front and fronts on the rear or maybe all four are fronts? I am thinking a bias problem. [I have a drum brake 63 never worked on the vette disc systems]
Brgds,
Rene

vipervetteguy

See post #37

vipervetteguy

Don't mean to brag, but I was a former power lifter who is now a serious cyclist......my legs aren't the problem!