low drag caliper/ guick take up mc

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low drag caliper/ guick take up mc

Postby jim327monza » Sun Sep 07, 2014 9:04 am

Hi, I am trying to solve my low brake peddle issues. s-10 conversion disk /drum. 76monza master and booster and combo valve. Calipers , wheel cylinders, mc,
booster and combo valve all new. System has been bled to ensure no air. After more research I find that S-10 calipers are of the low drag design and require a
step or quick take up master cylinder. If any one has knowledge of this set up the help would be greatly appreciated
As always, Thanks for the help Jim H
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Re: low drag caliper/ guick take up mc

Postby cosvega76 » Mon Sep 08, 2014 8:02 am

Jim,

A Quick Take-Up master has a larger bore next to the pushrod end and a valve in the primary reservoir. As the pedal is pressed, the larger bore moves a larger volume of fluid to the front calipers until a certain pressure is met and the primary piston is past the compensation port. At that point, the brake system functions normally and the excess volume from the quick take-up bore is vented into the primary reservoir.

The problem with the H-body using one of these masters is that the register in either the firewall or the brake booster is smaller than the boss of the master cylinder (because of the larger bore for the quick take-up portion). You may need to adapt an S-10 brake booster to use one.

Make sure there is no excess movement in any of the caliper mounting hardware, wheel bearings, or taper in the brake pads. These will also cause a long pedal. Did you change from manual to power brakes? If so, did you change to the lower pin hole on the brake pedal?


Chuck
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Re: low drag caliper/ guick take up mc

Postby 1100kaw2 » Mon Sep 08, 2014 11:21 am

Had same problem with my set up.
bleed bleed bleed, pump pump pump. I even used power bleeder. still had crappy pedal.
I found out about the quick take up info, etc...
I was told that unless you specifically ordered quick take up calipers, like from speedway or something, that the chances you have them are slim. all the aftermarket, rebuilt stuff will prob. not be quick take up style.
That being said, the difference is in the machining of the caliper bore and piston. I don't think you can tell by just looking at them.
I ran into a guy on another forum that recommended a residual check valve in rear line.
He said even if rear drums adjusted up correctly, the return springs pull them in and cause the pedal to travel too far before it starts to pressure up system.
I installed a 10 lb.(red) check valve from Jeggs, $18. Made everything much better.
I am still contemplating doing 2 lb.(blue) valves in the front.
I'm gonna wait till I get to drive it more before I do.
Hope this helps.
Darrell


72 LS-5spd.
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Re: low drag caliper/ guick take up mc

Postby 1100kaw2 » Mon Sep 08, 2014 11:24 am

Just a note
I am not running factory style proportioning valve,( no valve) and I am non power.
Darrell


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Re: low drag caliper/ guick take up mc

Postby jim327monza » Mon Sep 08, 2014 8:31 pm

Chuck, Darrell, Thanks for the reply. From the information I have gathered, 90% of gm calipers for mid-size cars from 1980 to 1988 (5 1/2" bolt spacing) were low drag units. Their are two ways to make this work. 1; order aftermarket calipers for the s-10 set-up and specify non low drag. Be sure to match the piston size to the bore of the master cylinder. 2; swap out the monza mc to the step-bore from the s-10. Getting rema calipers from the box auto store is a crap shoot because the reman guys have lumped all these calipers together and you don't know what you are getting. (bendix, as well as several other well known supplier have issued tec warnings about this). At this point I am leaning toward putting in the full s-10 set up. I will be at the Charlotte Auto fair next week and will see what i can find out. I will let you know if I find anything useful.
Thanks Jim H
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Re: low drag caliper/ guick take up mc

Postby 76wagon » Tue Sep 09, 2014 7:43 pm

Jim, I'm running the same setup (except for an aftermarket booster for a little extra clearance) and ran into the same problem. All new parts, no leaks, bled it a million times, bench bled the master a few times, replaced the master, no better. Turned out the master cylinder was no good, so was the second. The third one was a different brand (Wagner) and works awesome.


I had never had a problem getting brakes to bleed out properly before, everything has always worked the first time. I figured the Monza masters were probably sitting on the shelf for years before I got them and the seals had dried out or something. Also when I brought it to the mechanic for a safety I let them try just in case I was missing something, they had the same results.


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Re: low drag caliper/ guick take up mc

Postby jim327monza » Thu Sep 11, 2014 7:50 pm

Phill, I agree that the monza masters probably have been sitting on the shelf for a while. This is one reason that I am considering the full s-10 swap. I need to check fit for the vacuum booster and push rods. the s-10 components should be fresher and more readily available. Just depends on hoe much is involved to do the swap. I will be at the charlot auto fair next week and will check their for more info.
Jim H
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Re: low drag caliper/ guick take up mc

Postby jim327monza » Mon Oct 27, 2014 6:42 pm

At last, a solution to my low brake pedal !!! After a lot of research (Thanks to everyone who replied to my post) I found my problem. Quick take up master cylinder? no! Low drag calipers? no! Bad MC? Bad calipers? Bad wheel cylinder? No,No.No!!! AIR? Yes, Yes Yes! I went through 3 quarts of fluid bleeding the system to no avail. Pressure bleed vacuum bleed reverse pressure bleed. Nothing. I went old school, had the little woman pump the brakes while I open and shut the bleed valve ( I wont go into what she thought about that). Air was trapped in the lines where they go over the rear axle , the high point. I put the rear of the car on jack stands high enough to put the bleed valve near level to the hump, left it overnight and rebleed the next day. Repeated the process for the front. I now have a high, firm pedal, and can lock all 4 tires with heavy pressure. I hope this will help some other poor SOB not to half to go through what I did.
As always. Thanks for all the help and I'll be back after a trip to the alignment shop. Jim H
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