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#915371 - 01/27/12 04:18 PM Re: can i install an adjustable prop valve [Re: Furgie]  
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SickSpeedMonte Offline
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SickSpeedMonte  Offline
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MD
Did you gut the stock combo valve when you installed the adj prop?

#915379 - 01/27/12 04:56 PM Re: can i install an adjustable prop valve [Re: SickSpeedMonte]  
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markg Offline
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nj
no


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#915495 - 01/28/12 04:51 AM Re: can i install an adjustable prop valve [Re: markg]  
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MADMIKE Offline
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MADMIKE  Offline
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C.V. CA
Originally Posted By: markg
no

Originally Posted By: StopTech

We’ll start here with three of the most basic rules regarding proportioning valve installation and selection.

1. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed if the factory unit is still in place. Proportioning valves in series with one another can do nasty, unpredictable things!

2. If you have the deeply-rooted need to install your own adjustable proportioning valve, be advised that they should NEVER be installed in-line to the front brakes. The effect would be to make your vehicle rear-biased before you could say “terminal oversteer.” Front brake line pressure should always be left alone – only the rear pressures should be considered for proportioning.

3. In all cases, the basic brake system balance needs to be close to optimized to start with. This is the only way that a proportioning valve can be effectively utilized. You should never assume that simply adding a proportioning valve will address all rear-bias conditions, as even the best proportioning valves must be well-matched to the target vehicle.


Take note of 'brake balance needs to be close to optimized'. A PV won't do squat if the balance is upset. Currently your rear drums/wheel cylinders are too big. Put them back to the 9" drums.


-Michael
Where the hell is JMD?!
#916090 - 02/01/12 01:21 AM Re: can i install an adjustable prop valve [Re: MADMIKE]  
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markg Offline
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nj
i put brake cyls from a 1 ton chevy truck in over the weekend.what i had was 15/16 and the ones now are 1-1/8 there is even one larger at 1-3/16 but i didnt want to go that far.the pedal def takes a bit more effor to stop now and i cant lock it up unless i stand on it.i dont think i would ever apply that much pressure.it still seems to stop very well but i still also have my manual prop valve that i installed all the way shut.im going to go with this i think.
now i need to get some good shocks for the front.i have kybs now that are at least 6 yrs old so they should be replaced anyway.
because my front is higher i would like to go with something at least 1 or 2 in higher.
any suggestions?


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#916249 - 02/01/12 10:59 PM Re: can i install an adjustable prop valve [Re: markg]  
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MADMIKE Offline
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MADMIKE  Offline
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C.V. CA
Originally Posted By: markg
i put brake cyls from a 1 ton chevy truck in over the weekend.what i had was 15/16 and the ones now are 1-1/8


Originally Posted By: markq
there is even one larger at 1-3/16 but i didnt want to go that far.



markg the modifications you have performed to the braking system would be best undone.

The rear brakes need to be put back to the 9" drums and 3/4" wheel cylinders they once were.
Originally Posted By: markg
the pedal def takes a bit more effor to stop now and i cant lock it up unless i stand on it.

You created a rear bias brake system with the 11" drums and 15/16" wheel cylinders. The bias is further rear with the increased wheel cylinders size of 1-1/8". You have already discovered to your chagrin that a rear biased brake system will cause the car to spin. Yet you continue to increase you're rear brake bias.

Why?

Originally Posted By: markg
i dont think i would ever apply that much pressure.

Did you think that before you spun and kissed the guard rail?

FWIW you cannot modulate drums as well as discs, the self-energizing effect limits this.

Originally Posted By: markg
it still seems to stop very well but i still also have my manual prop valve that i installed all the way shut.

The only reason you are still able to stop with this horrible bias is due to the quick take up design of the MC.

Originally Posted By: brakeandfrontend.com
When the pedal is depressed, the large bore piston closes the quick take up valve and forces fluid past the primary piston seals until a backpressure seals the primary piston. This is called take up mode. After this occurs, fluid from the large bore is returned to the reservoir through check valve in the center of the valve. This is called compensation mode.


The stock MC is a 23.8mm/36mm quick-take up design. Initially the MC is effectively a large 36mm bore MC. This allows the pads/shoes into contact with the discs/drums quickly. When they make contact the system begins to build pressure, when it equalizes across the 23.8mm bore piston, this seals the smaller piston and the check valve in the MC opens. Then the MC effectively becomes a 23.8mm bore MC. Automakers did this to reduce drag while still maintaining normal brake pedal feel.

What you have done markg with the larger rear wheel cylinders the MC is in 'take up mode' for a longer time as it requires more pedal travel to actuate the larger rear wheel cylinders. When the system begins to build pressure, the MC still requires even further pedal travel to build enough pressure to actuate the metering valve. Then finally the front brakes begin to work.

To compensate for this you now are using an adjustable PV to try and reduce pressure/flow to the rear wheel cylinders in an effort to have your car stop. This is not how the PV works. It is a fine tuning device on an optimized brake system. Since you are no where near optimized with the jantastic wheel cylinders attempting to bandaid the problem by closing the PV as much as possibly has given you a car that stops, but not in a safe manner.

The brake system is just that, a SYSTEM. Any changes done should be done with consideration to the system as a whole.
Remove that adjustable PV, reinstall the stock PV, install the original 9" rear drums and 3/4" wheel cylinders.
When you have done that, THEN we can begin improving your brake system.

Whomever is suggesting to use 11" rear drums and 1-1/8" wheel cylinders is going to get you killed... Unless you enjoy doing 180* spin outs on the freeway.

Center punching a pole with the rear of an G coupe does wonders for the gas tank.

Last edited by MADMIKE; 02/01/12 11:03 PM.

-Michael
Where the hell is JMD?!
#916347 - 02/02/12 02:26 PM Re: can i install an adjustable prop valve [Re: MADMIKE]  
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markg Offline
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nj
thanks for taking the time to pound this into my head.
the9 inch drums are going to go back on.i assume i can leave the adj prop valve inline and leave it all the way open.

i am def going back to the old systen but
didnt early montecarlos have 11 inch drums with the same setup we have in the front?


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
#916356 - 02/02/12 03:25 PM Re: can i install an adjustable prop valve [Re: markg]  
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Furgie Offline
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Rustbeltville,MA
g.m.s been using the same 9" drums for ages


Oh when your body starts to shake,It's time to loosen off the brake ,and slam the hammer down
#916483 - 02/03/12 07:42 AM Re: can i install an adjustable prop valve [Re: markg]  
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MADMIKE Offline
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MADMIKE  Offline
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C.V. CA
Originally Posted By: markg
i assume i can leave the adj prop valve inline and leave it all the way open.
If the factory prop valve is not disabled, you should not have the adjustable unit installed. Adjustable PVs cannot be 100% open nor 100% closed. There still is a knee point.
If you have gutted the factory prop valve and installed the adjustable unit, you do not want to leave it open. You will need to fine tune for maximum stopping power.
Referring back to the MM instructions for the Wilwood installation...
Originally Posted By: MM BPV-1
NOTE: Even at full “increase” on the knob the rear line pressure will still be slightly lower than the front line pressure. It is impossible to have higher pressure in the rear lines than the front lines with this valve.

The rear brakes should never lock before the front. To be sure this doesn’t happen, start with the valve fully toward the “decrease” setting. Test hard braking in a safe and controlled environment. A race track is recommended. Adjust the proportioning valve toward “increase”, until the rear brakes begin to lock at the same time as the front. At this point, turn the valve toward “decrease” until the rear tire lockup just goes away, and only the front tires lock up. This setting will give you greatly improved braking power and directional stability

Originally Posted By: markg
i am def going back to the old systen but
didnt early montecarlos have 11 inch drums with the same setup we have in the front?

No.
The 1st and 2nd gen Monte Carlos(116" WB) used 11" front rotors with 75mm calipers and 9.5" rear drums with 15/16" wheel cylinders.

The 3rd and 4th gen Monte Carlos(108"WB) used 10.5" front rotors with 63.5mm calipers and 9.5" rear drums with 3/4" wheel cylinders.

If you are looking to upgrade your brakes, the 3rd and 4th gen F bodies have better systems. The '98-up 2wd Blazers also offer a better brake system that is more of a bolt on for the 78-88 A/Gs.


-Michael
Where the hell is JMD?!
#916496 - 02/03/12 02:12 PM Re: can i install an adjustable prop valve [Re: MADMIKE]  
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markg Offline
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markg  Offline
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nj
thank you so much.
thanks for taking the time to educate me on this subject!
in the beginning i really thought that this would be an upgrade but this is something best left to the experts.


86 ss 86 cl,330hp GM vortec cratemotor-700-r trans worked,ford 9.5 inch rear with 3-50s,custom 3 inch exhaust with flowmasters.
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