[gtorich]

Ok, couple questions here for you guys...........trying to make a long story short........got new rotors & calipers, bleeded the brakes good, no issues......

Have a very hard pedal..........thought maybe the booster might be bad or the check valve, did the pump a few times and start the motor..........on the very first pump the pedal only went down maybe a inch, second pump about a half inch, 3 pump barely moved, started car and the pedal maybe moved a half inch.

When car was off, i pulled the check valve out, got a hiss sound for a second..........also when running the motor i pulled the check valve out, ran a hair rougher, the idle speed when up.

When hooking up a vacuum gage at about 800 ish rpm, i get between 12-13, if i move the idle screw up some to 900 ish, i get about 13-14...........this is never steady, seems to jump around some.........if i give it some gas it will stay at about 18 or so and pretty much steady.

The cam is an Old Faithful in a 463

The car does stop, nothing to brag about though, the brakes will not lock up.

So im looking for some advice on what to check or do next

Rich

[Geoff]

Judging by the tests you have done so far, it sounds like the booster & M/C are working.....as best they can.

Discs require about 50% more line pressure to achieve the equivalent stopping power of drums brakes.

Two things to get more line pressure is a [1] smaller diam M/C or [2] larger diam booster or dual booster.....or a combination of both.

I changed to discs &, like you, didn't like the reduced stopping power. Went back to factory drums & now the car stops!
. Mr. Pontiac knew what he was doing!

[Scarebird]

Shoot a pic of your booster.

[ta man]

Do you still have a check valve in the vacuum line for the booster? Confirm that it is in the proper orientation.

[gtorich]

Originally Posted by Scarebird

Shoot a pic of your booster.

Scarebird, couple pics for you.

I did read about some S-10 duel booster..........the pics of that looked pretty big, im hoping to not have to mess with these brake lines........seems everytime i mess with those, bad things happen. lol.............not sure on the hydro-boost.

Rich

[Scarebird]

Yeah, your booster is way too small. You will need a dual 9" with that cam. Or switch to hydro boost or manual.

[ta man]

Originally Posted by Scarebird

Yeah, your booster is way too small. You will need a dual 9" with that cam. Or switch to hydro boost or manual.

The cam isn't the issue.

[Scarebird]

Your vacuum is too low for that booster; the cam defines the vacuum.

Hard pedal is indicative of low vacuum, assuming the booster is working correctly to it's ability.

[ta man]

Originally Posted by Scarebird

Your vacuum is too low for that booster; the cam defines the vacuum.

Hard pedal is indicative of low vacuum, assuming the booster is working correctly to it's ability.

What's the difference between the OP's booster and a stock 2nd gen firebird booster with either disc or drum brakes and others that have used stock boosters with the OF cam?
Like I said..if the engine is pulling 13 inches of vacuum don't blame the cam..many others run the same cam with zero issues with stock boosters.

[Scarebird]

That is not the stock booster, most likely a 9" or 10" single aftermarket. Do the math with surface area vs. 11" and you will answer your own question.

Stock 11" single diaphragm are good to about 11 inHg, single 9/10's like the one shown are mid-teens; hence his issue.

Dual 9" work at least to 9 inHg from personal experience.

[gtorich]

Hey, thanks guys......the booster is a 9 inch one.........im hoping i can try a dual 9 inch, im just worried about having to move the brake lines...........when i first got the car it had manual disk..........another thing i should have just let alone, cant go back to manual without messing with the brake lines, which i hate doing.

Hopefully someone that put a hydro-boost on a 66-67 can chime in if they had to mess with the brake lines.

Rich

[Scarebird]

You have serious issue, you will need to mend it.

You may be able to get flex lines to fit.

[Scarebird]

Fittings that will adapt to GM master:

1/2-20 to 4-AN

https://www.summitracing.com/parts/ear-562046erl

1/2-20 to 3-AN

https://www.summitracing.com/parts/ear-562046erl

9/16-18 to 3-AN

https://www.summitracing.com/parts/ear-562048erl

9/16-18 to 4-AN

https://www.summitracing.com/parts/ear-562049erl

May also work with the combo or distribution valve. You can look up hoses with the AN fitting easy enough.

Mark

[gtorich]

Originally Posted by Scarebird

You have serious issue, you will need to mend it.

You may be able to get flex lines to fit.

Scarebire, i take it your saying no matter what i do, duel 9 inch or hydro-boost, im gonna have to mess with the brake lines...........oh boy.


Ta man...........im taking it your talking about the yellow piece going into the booster, thats the only check valve i have...........im assuming the check valve is bad if you can blow thru it, and seeing i have "crs" syndrome......had it off yesterday thinking if i blew air from the check valve it came out the hose, but if i blew on the hose end nothing came out of the check valve.

I dont mind moving lines around , i just hate working with that Dot 3 trash......stuff has wrecked enough paint on me..............gonna look into if i can get the whole deal switched over to Dot 5...........dont know what that takes to do, you would think everyone would do it if it was easy.

Thanks for the reply's guys

Rich

[Old Goat 67]

DOT 5 for 38 years and Hydroboost for 13. Wouldn't go back for anything!

It is easy. Clean out old DOT3 with denatured alcohol, new rubbers everywhere, pressure bleed whole system with DOT 5 in master.
Like having a monkey in the trunk with an anchor and a chain.

[Scarebird]

I have no direct experience with DOT5. Steal a turkey baster from your wife and siphon out the fluid from the master before starting. Manual masters work well too, roomy and cheap. A good flare kit (Blue Point) is a must if making your own lines and avoid stainless, not needed and a royal pain to flare - use Cupronickel.

[gtorich]

Originally Posted by Scarebird

Fittings that will adapt to GM master:

1/2-20 to 4-AN

https://www.summitracing.com/parts/ear-562046erl

1/2-20 to 3-AN

https://www.summitracing.com/parts/ear-562046erl

9/16-18 to 3-AN

https://www.summitracing.com/parts/ear-562048erl

9/16-18 to 4-AN

https://www.summitracing.com/parts/ear-562049erl

May also work with the combo or distribution valve. You can look up hoses with the AN fitting easy enough.

Mark

Mark, thanks for the info.........

Old Goat 67...........thanks will look into this deal.

Rich

[Lemans64]

I have a Hydraboost on my 64, Hydratech model. With prop valve on the side. Works very well, but take a kittle getting used to.
Prepared for face plant on dash, LOL. I had 9" booster on mine and did not have enough vacuum to work properly. Used a vacuum reservoir for a bit that did help a little.
Went to vacuum pup after that, it worked but was noisy and could feel vibration in car when it came on. hydra boost and have never looked back.
Lines did require some slight bending, but nothing where i had to remake them.

[Chris65LeMans]

I have hydro boost with 4 wheel disks and love it.

You shouldn’t have to throw a ton of money at this, though. It sounds like you’re out of adjustment. If you hate working on brake lines, I’d consider finding a reputable shop to work on it. “The car Does stop” sounds pretty scary to me. Remember- the better your brakes, the faster you can go!

[autobahn]

I just went thru that ! my bet is you have a 1.125" bore master cylinder and you have hard brakes I went from a 1.125" Wilwood master to a 15/16" bore Wilwood master, and now I have the brake I wanted