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Old 10-30-15, 06:59PM   #1
Mr.Pontiac
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Default Told to buy Christmas gift now!!! Calipers

Nicce, family told me to be safe buy new & better calipers for the front of my 67 GTO. Running single piston factory units right now, Rotors have about 25 miles on them.Any suggestions on a nice set of calipers(i like red powder coated units). Some help here pontiac racers.My car will not hold car past 1500 rpm,s on starting line, i want something better!! Im listening!!!
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Old 10-30-15, 07:47PM   #2
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Yeah it's called a trans break and a line lock. Then you can come out at what ever rpm you want and not have to worried. The trans break locks first and reverse. So car won't move until you let go of the button. The line is just locks front breaks so you can do your burn out. If their going to spring for anything have them spring for a Trans break.
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Old 10-30-15, 07:49PM   #3
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I have found the factory front disks to be very good.The last owner of my bird put Baer breaks on and IMO was a waste of money.Do you have rear disc?If not that might be a better use of money but with that comes other issues.Tom
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Old 10-30-15, 10:01PM   #4
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Originally Posted by tjs44 View Post
I have found the factory front disks to be very good.The last owner of my bird put Baer breaks on and IMO was a waste of money.Do you have rear disc?If not that might be a better use of money but with that comes other issues.Tom
X2
My manual disk/drum has no problem stopping the car.
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Old 10-30-15, 10:29PM   #5
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Holding the car on the line is the first major problem,I tell momma stopping the car i can do if i have to stand on the pedal. She still worries. Tell me i have to pull the trans out again for a trans brake!!!
geeezzzzzz!!!! lol
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Old 10-30-15, 10:46PM   #6
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I cant believe with the med HP you have that your line lock wont hold that car!I would get a VERY good brake guy to look at your system.You have been cocking around with it so much there could be a issue your missing.Tom
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Old 10-31-15, 01:17AM   #7
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Sounds like the proportional valve isn't working properly. The majority of the persure gets applied to front disk brakes. Yep trans would have come out to install valve body.

Yeah...I would say if the brakes won't hold with you toqueing it up up to 2500-3000 you have a problem some were in braking system. Most likely proportional valve which allows you to adjust persure front to rear. Or just bad calipers or hoses that are collapsing not allowing enough pressure to disk brakes.
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Old 10-31-15, 03:23AM   #8
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Been in touch with the brakeman for 3 days, a proportioning valve, or whatever you want to call it should never be used on disc brakes.All the valves are nothing more than pressure reducing valves. On drum brakes all you need is250 TO 300psi to run them, thats why there are there but on a disc brake set-up you must have high pressure as much as 1000 psi to make them work proporly.My line lock bypasses the valve completely & he very very strongly suggests coming from master rightinto disc. brake line no valve of any kind!! vERY GOOD EXPLANATION ON LINE. He also explains why effient
disc are worst than drums. Only good thing from disc is its cooling charge alot faster than drums. Once again i have not had car out on the streets , go to www.Ramman.com watch the video.
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Old 11-23-15, 12:07AM   #9
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Mr. Pontiac,
Road racers use prportioning valves on 4 wheel disc systems because they have to get the balance between the fronts & the rears correct .If you do not you will put it into the ditch.
Same goes for street cars & drag cars.

Disc/Drum you have to use a minimum of a combination valve to balance the brake bias between the fronts & rears.
Make sure the combination valve you are using is NEW & not 50 years old.
The MC for disc/drum system will have a residual valve on the port of the rear resevoir that supplies the rears.


Have you acutally put a pressure gauge on the front brake circuit to see what the pressure on the fronts is when you pump up the brakes and activate the line lock?

I know if i try and make my line lock hold the car against the trans and give it too much throttle the car will start to push through the beams.
That's why the trans brake got invented.

Launching off the line lock(roll control) works best with a manual trans car cause you do not have three feet and don't want to rattle it forward after you are staged.
That'll kill it for ya if you are already staged deep.
If you end up going to a trans brake set up just fortify the trans with the biggest cooler & fan you can fit in front of the radiator.
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Old 11-28-15, 05:59PM   #10
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disc brakes all 4 corners
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Old 11-28-15, 08:13PM   #11
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disc brakes all 4 corners
You might go slower now more drag than drum brakes, very little though.
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Old 12-01-15, 02:41AM   #12
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Drums you could can back off the adjusters until there is zero drag but you will have a resulting low pedal that can spook you , especially on a fast car and no good for the street in panic stop situations.

Factory Sliding Calipers have a little more drag to them than normally adjusted drums and it is constant.

Four piston calipers not as much.

In the early 80's GM started using what they call "Low Drag" disc brake calipers.
Those require the use of a companion "Quick Takeup" master cylinder that causes the pistons to initially travel faster ( by pumping more fluid) to make up for the low drag caliper's built in clearance.

Most aftermarket retrofit brake kits do no use low drag/quick take up technology
.
Just remember that when working on a later model or when grabbing parts out of the yards. The parts just cant mix and match.
Check the interchange first.

Here is some more info 'esplaining about it:
Frequently Asked Questions (FAQs)
What modifications will need to be done to my “G-Body” or S-10 truck or Blazer to install the MANUALBRAKES.COM master cylinder brake plate?
When using the standard MANUALBRAKES.COM adapter plate without the retention cup, no modifications are necessary for all “G-Body” cars and 1st generation S-10 trucks (1982-1993) and S-10 Blazers (1983-1994). If using the MANUALBRAKES.COM adapter plate with retention cup, then there will be some trimming of the firewall to fit it properly on 1st generation S-10 trucks and Blazers. If done correctly, this will not cause any problems if converting back to power brakes. All vacuum boosted power brake equipped “G-Body” cars and all 1st generation S-10 trucks and Blazers have provisions in the brake pedal for manual brakes. This brake pedal provision is an extra hole drilled into the brake pedal from the factory to allow the use of manual brakes. The MANUALBRAKES.COM adapter plate uses these factory provisions to convert your vehicle to manual brakes.
On 2nd generation S-10 trucks (1994-2003) and Blazers (1995-2005), there is a need to have modifications done to the firewall because these years where never equipped with manual brakes from the factory. A 2” inch hole will need to be cut in the firewall centered between the top two holes that the vacuum booster bolted to for clearance of the master cylinder and the pushrod retention cup.
What is the piston size of a “G-Body” and S-10 caliper?
Stock piston size is 2.38”.

Caliper Specifacations of Aftermarket "Metric" Calipers

Caliper...................................Part Number...........Advertised Bore Size.......Actual Piston Size.....Weight
Wilwood 2" Bore Caliper.........PN 120-9333............2.00"............................. ....1.981"..........................4lb 1.6oz
US Brake / AFCO Caliper.......PN 7241-9004..........2.50"............................... ..2.376"..........................6lb 4.7oz
CCP Big Bore Caliper.............PN CP412526..........2.75"........................... ......2.565"..........................6lb 11.2oz
Wilwood 2.75" Bore Caliper....PN 120-8926............2.75"............................. ....2.704"..........................4lb 8.6oz

What is the bore size of a master cylinder on a “G-Body?
Manual brake master cylinders are 7/8” and are cast iron. Power brake master cylinders come in 24mm strait bore and a step bore version with a primary bore of 24mm and a secondary bore of 36mm. Most of the strait bore master cylinders where cast iron, though some power boosted versions where aluminum. The stock step bore master cylinder came in aluminum. Any new step bore master cylinder made today will be made of cast iron.

What is the bore size of a master cylinder on an S-10?
Manual brake master cylinders are a step bore design and have two different bore sizes. The bore sizes are 24mm and 31.6mm and where originally aluminum from the factory. Most power brake master cylinders came in 24mm and 36mm step bore and where originally aluminum from the factory. Any new step bore master cylinder made today will be made of cast iron.

What modifications should be done to the stock braking system?
If using the stock brake components, make sure all parts of your system are in good working order. Vacuum assisted power brakes will mask some faults in the brake system that a manual brake system will not be able to cover up. It would be good to replace old rubber brake lines with good aftermarket steel braided lines. Steel braided lines allow less “ballooning” that can happen with rubber brake lines and will contribute to brakes that feel spongy. Quick take up (low drag) calipers that came on most “G-Body” cars, S-10 pickups and blazers, and the third generation camaros and firebirds will require a step bore master cylinder. Another upgrade would be to a NON low drag calipers and a standard, strait bore master cylinder in a 7/8" bore. Upgrade to aftermarket pads.

What are quick take up (low drag) calipers?
In early 1980s GM introduced the quick take up (low drag) caliper on most of its vehicles. The reason for the quick take up (low drag) caliper was the energy crisis. The quick take up (low drag) calipers were designed to reduce the friction between the pad and the rotor to improve gas mileage.
The engineers at GM found that changing the square cut seal groove on the caliper could cause the caliper piston to be pulled back twice as much as the conventional caliper. The quick take up (low drag) caliper is designed with a 30 degree bevel in the seal groove as opposed to the conventional calipers 15 degree bevel. With twice the bevel, there is twice the seal flex. Flexing the seal two times as much pulls the caliper piston back into the caliper bore 2 times as far creating no drag of the brake pad on the brake rotors.

What’s the problem with using a quick take up (low drag) caliper?
The volume of fluid needed to take up the extra gap created by the quick take up (low drag) caliper exceeds a conventional master cylinder's capacity so a step bore master cylinder is needed. A stop bore master cylinder provides a large volume of fluid initially to take up the gap and then internal bypass valve switches the master over to a high pressure system where it acts as a conventional master cylinder. Quick take up (low drag) calipers require a step bore master cylinder to function correctly.

How do you visually check if your calipers are a quick take up (low drag) design?
“G-Body”, S-10, and 3rd generation F-Body vehicles use the same caliper design. Conventional calipers where used from 1978 to 1980 on the “G-Body” and quick take up (low drag) calipers started where used from 1981 to 2002 in “G-Body”, S-10, and 3rd generation F-Body. Because the calipers are the same design, externally there’s no way to tell because the quick take up (low drag) calipers are mixed in with conventional rebuilt calipers.

How do you physically check if your calipers are quick take up (low drag) design?
To check if your caliper is a quick take up (low drag) engineered, perform the following test. Purchase or rent a pair of brake hose clamps at an auto parts store. Press the brake pedal as it is and then clamp off the two front rubber hoses. If the pedal returns and is high and firm, chances are you have quick take up (low drag) calipers. Be aware that the same symptoms will occur if the bleeder screw is not in the 12 o’clock position when mounted on the spindle or there is still air in the caliper.

Can you use quick take up (low drag) and step bore master cylinder with manual brakes?
Yes. This is how it was done from the factory in the 1st generation (1982-1993) S-10 trucks, but they are not known to be very effective when braking. The stock front S-10 quick take up (low drag) calipers, 2.38” bore, are too small compared to the stock S-10 master cylinder step bore of 24mm and 31.6mm. This will cause a harder than normal pedal and there is insufficient clamping force produced by the system to make the braking effective. The stock S-10 step bore master cylinder is the smallest step bore master cylinder made. A 7/8” strait bore master cylinder is recommended, but can not work with the stock front quick take up (low drag) calipers. Since a more effective 7/8” bore master cylinder is recommended, an upgrade to larger 2.75” bore calipers are also recommended. A smaller bore master cylinder bore equals more brake fluid pressure at the caliper and a larger bore caliper equals more clamping force on the rotor.

What is a metric brake caliper?
A metric brake caliper where designed to be used on the GM metric chassis (1978-1988 “G-Body” cars). It is a floating, single piston design with 2.38” piston. The metric brake calipers where used on 1978-1988 “G-Body” cars, 1982-2003 S-10 trucks and SUVs, and 3rd generation F-Body (1982-1992 Camaro / Firebird) vehicles. Aftermarket metric calipers come in bore sizes of 2.75” bore, 2.50” bore, 2.25” bore, and 2.0” bore. Most aftermarket metric calipers are designed as conventional calipers and are not a quick take up (low drag) design. All metric calipers have a slide bolt center to center spacing is 5.50 inches and use a D154 brake pad.

What is a “G-Body” vehicle?
Technically, G-Body vehicles are the GM intermediates chassis designation made from 1981 to 1988. The GM intermediate vehicles from 1978 to 1980 also used the same chassis and are technically “A-Body” chassis. For simplicity and to avoid confusion, the 1978-1980 “A-Body” vehicles are lumped in with the 1981-1988 “G-Body” vehicles.
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Old 12-02-15, 10:06AM   #13
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The D-52 caliper is an excellent caliper.. I like the Carquest Ceramic pads.. An adjustable proportion valve along with a stand alone metering valve is mandatory with our hills..

As far as rear brakes, even with self adjusters they need adjusted manually to get full braking.. Jack the rear end up, release the brake and turn the star wheel with a brake spoon until you hear a light but constant scraping sound..

If no self adjusters, make sure the spoon is going in the up words direction on both sides to tighten..

On my 64, I pulled all that self adjuster junk out of there years ago and adjust manually twice a year, that's about 5-8 thousand miles for me..

Also, you can adjust the front disc brakes for drag by using alignment shims on the top bolt.. I have my Scarebird brackets set perfectly so there is almost no drag..

I can stand on my brakes at 100+ and my car pulls down with a nice controllable stop without and wheel lock up..

With A bodys, my Chevy buddy puts either 11" or 12" drums on the back of his A body cars, I forget which one..
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