just can´t get my brakes working

[camaro427-69]

swapped over to ssbc brakes but can´t get them working right. i brake bleeded 4 times but still almost no brakes. engine is a 468 bbc with a nice cam but still i´m getting 13-14" in idle and it jumps up to 16-17" when i hit the throttle a bit. using a comp cams vacuum canister. power booster is holding vacuum a long time. if i pump the pedal and start the engine the pedal travels about 1" down. pedal is not spongy and it stays hard all the time.

anybody some more advise please?
thanks,
pat

[MrQuick]

Are you getting good fluid flow at the calipers bleeders? When you say "aren't working" is this not stopping ,is this when driving?

[camaro427-69]

yep fluid without any air bubbles. when i hit the brakes the car slows down but really slow and i need to keep big distance to other cars to make it. i just ordered an electric vacuum pump maybe it´s gonna help a bit........

[MrQuick]

You should be able to stop it without the assist.

Are the calipers the 6 piston type? I had a problem with those before. Required a large piston master cylinder to fill the calipers.

See how far the pistons come out when depressing the pedal then see how far the pistons retract.

[David Pozzi]

What caliper piston bore sizes, and what bore size master cyl?

[chicane67]

Sounds like the PV ratio.

I would question the master cylinder vs caliper bore size mismatch... as David is questioning.

[camaro427-69]

master cylinder and everything else is stock drum disk 69 camaro. ssbc quick change caliper, so just 2 piston shouldn´t be a huge difference. it stops but i have to press the pedal real hard and breaking performance sucks. worked better with the old stock disk brakes........

[Tito]

SSBC "Force 10" Q/C calipers have twin 38mm pistons vs. "stock" single 2 15/16" piston. That makes for a total piston area of ~3.5 sq in with the SSBC calipers versus ~6.77 sq in with stock. That means you'll need almost twice the pedal effort for the same master cyl. Even if you go to the "heavy duty" Force 10's with 43mm pistons, you're only looking at ~4.5 sq in of caliper piston area (50% more pedal effort than stock). (which ones do you have?)

Best to ask SSBC what master cyl they reccomend, but with the 44mm calipers, I'm thinking about a 1" bore master (68 vette manual brakes master), probably something in the 7/8" range for the 38mm calipers (?) This would put the hydraulic advantage between the master and caliper in the ballpark of the stock setup.

Dave/Chicane will provide more better-er info :)

[chicane67]

I'm with you Tito... a master between 0.875" to 1.000" would be just about right... and the math says the same.

Obviously, the 0.875" will be a little more sensitive to modulation... but I believe the 1.000" would be right near stock feel.

[camaro427-69]

its the 185-s kit with the twin 38mm piston. i´ll try to get one of those master cylinders. i´ll let you know if it helped.

thanks a lot guys
pat

[camaro427-69]

btw. just checked summit and they offer master cylinders with 1.125 bore size for 69 camaro´s. is it wrong to go bigger? do i need changes at the brake lines/booster for that?..........

thxs

[6'9"Witha69]

Do not go bigger as you need more pressure from the smaller bore as opposed to volume with the larger bore. Look at the wilwood masters. They have a 7/8" which will be perfect.

[Tito]

btw. just checked summit and they offer master cylinders with 1.125 bore size for 69 camaro´s. is it wrong to go bigger? do i need changes at the brake lines/booster for that?..........

thxs

Most likely, you the m/c you currently have is 1.125" -- that's the stock size for power disc/drum. Swapping it out for another 1.125" m/c probably won't help your situation (unless the m/c you have is toast for some reason). VERY similar to stock master, but with a 1" bore is a master cyl for 67-76 corvette with manual brakes. This should bolt right up and are typically dirt cheap (at least here in the states). Of course, that means it's also cast iron, so if you're looking for polished aluminum or whatever, the SSBC units may work fine.

FWIW, the part nums for the 1" bore vette m/c are:
CARDONE 101371 (http://info.rockauto.com/Cardone/Detail3.htm?/10/101371-01.jpg)
Raybestos MC36367 (http://info.rockauto.com/Raybestos/Detail.html?MC36367-7.jpg)
Dorman M36367 (http://info.rockauto.com/RB/Detail2noTip.html?http://www.dormanproducts.com/images/items/hwrap1/UM36367.jpg)
AC Delco 18M27 (http://198.208.187.182/internet/PartImage.jsp?mfgname=ACDELCO&prodlinecd=14&acpartnbr=18M27)
(info according to RockAuto.com, I'm assuming it's correct)

[camaro427-69]

yeah, got it! i´m more of an engine guy.....bigger bore means more bang :fingersx: . i´ll try to get one of those, they are really cheap.

thanks for the information