Manual Brakes (Not feeling so good)

[1988 Olds]

Hey guys I recently swaped to manual brakes on my cutlass. I made my own block off plate and used a S-10 master cylinder. The brakes just don't feel that strong to me. I have been reading people are using larger wheel cylinders in the rear from an S-10 but my dad checked today and the threads on my car are M10X1.25 and the wheel cylinders from an S-10 are listed as 3/8-24. Can anyone help me out here.

 

[SBCregal]

which threads? where the brake line attaches to the wheel cylinder?
if so, you could get adapters to go from one to the other

 

[Coveted]

manual brakes mean you have to stop on them hard or it dosent stop, like push the pedal as hard as you can
I had no power booster on my race car, trust me, nightmare to stop

 

[joe_padavano]

manual brakes mean you have to stop on them hard or it dosent stop, like push the pedal as hard as you can
I had no power booster on my race car, trust me, nightmare to stop

I have factory manual discs on my 70 W-30 and it stops fine. I wonder if the problem isn't one of pedal ratio. On the older A-body cars where you could get either manual or disc brakes, there are two different holes for attaching the pushrod to the master cylinder (or power booster). The manual brakes use the hole closer to the brake pedal pivot, the power brakes the one further away. This difference in pedal ratio makes all the difference in the world as far as pedal force is concerned. As with any lever, however, you're trading pedal force for travel distance - the longer lever arm with the pushrod in the manual brakes position requires longer pedal travel for the same fluid displacement out of the master cylinder.

I'm assuming the G-body brake pedal only has one hole for the pushrod? If so, I'd try drilling a second hole about an inch above the factory one to change the ratio.

 

[Uncletruck]

The second hole for the pushrod Joe speaks of is present on the G body brake pedal. It might give you some more leverage, but if you are just using the stock G body brake setup without the power boost, it's just going to be unbearable and dangerous if driven on the street as it was designed to be a power boosted setup unlike a car set up with factory manual brakes.

-UT-

 

[85 Cutlass Brougham]

I have factory manual Disc/Drum brakes on my AMC and it stops OK....but not great-even with all new lines, calipers, master, pads, etc. If you have the pushrod in the wrong pedal hole, it will be very hard to stop. I know that from experience. It took both feet to move the pedal. I think it needs to be in the upper hole for more leverage with manual brakes.

 

[1988 Olds]

Yes there are two holes and we already have it in the top hole. Like uncletruck said its not really safe at all to drive on the street. I drove maybe 2 miles yesterday and decided it wasn't worth crashing my car just to have it out and about.

SBC Regal - Do you know of anywhere that has them. A link would be awesome.

 

[joe_padavano]

The second hole for the pushrod Joe speaks of is present on the G body brake pedal. It might give you some more leverage, but if you are just using the stock G body brake setup without the power boost, it's just going to be unbearable and dangerous if driven on the street as it was designed to be a power boosted setup unlike a car set up with factory manual brakes.

-UT-

I guess I'm surprised by this. I've never driven a G-body with unboosted brakes, but my 70 W-30 weighs more and has the same 10.75" front rotors and 9 x 2" rear drums. The only differences I could imagine are the piston diameters in the calipers and rear cylinders and the bore of the master cylinder. As I said, my 70 came from the factory with manual discs and the bores are all sized accordingly. I have absolutely no problems stopping this car on the street, even when, ah, taking full advantage of the big block Olds.

 

[pontiacgp]

Hey guys I recently swaped to manual brakes on my cutlass. I made my own block off plate and used a S-10 master cylinder. The brakes just don't feel that strong to me. I have been reading people are using larger wheel cylinders in the rear from an S-10 but my dad checked today and the threads on my car are M10X1.25 and the wheel cylinders from an S-10 are listed as 3/8-24. Can anyone help me out here.

the wheel cylinders from the S10 are a direct replacement for the G body wheel cylinders. The wheel cylinder your looking for is a non power brake wheel cylinder. The cylinders are the same size as the G body but the piston in the cylinder is larger. I have the S10 cylinders in my GP for years.

As far as the discussion about non power brakes being unsafe I help out on a G body race car that has no power brakes. The front end has been upgraded to camaro spindles with the 11" rotors. The rotor and pads are being replaced due to one rotor being cracked in 2 places and the pads have been deformed from the pressure of the caliper piston. The driver of the race car is 15 years old and he's not the hulk so if he can do it with no problems I don't understand why anyone would claim it to be unsafe in a daily driver.

 

[1988 Olds]

Thanks for the help guys. I think we must just be doing something wrong. We are going to test the pressure at the wheels tonight or tomorrow. Maybe a bad master clylinder, who knows?

pontiacgp- do you have a link or a part number I could look up, again thanks for your help