front discs - opinions on quick take up masters 79-87+

[Chuck78]

Eventually I'm doing a front xmember swap for to gain 5 lug discs and $10 ball joints (vs $120 and $60 lower and upper for a 62), and I got a 73-87 xmember and booster/master/prop valve from the same 89 suburban (73-91 burbs are samebody/chassis as 73-87 pu's).

I didn't want the quick take up MC because of the plastic reservoir and modern look that it'd add to m6 62 GMC. THen I started reading up on it, and realized that they are designed for less drag and better gas mileage... This made me think twice about them, although I still don't like the look (rather have cast than parts plastic).

How many people run them, and how many of you have good opinions of them, or good/bad experiences? My winter beater 89 burban has one, but I never gave it any thought. Got same year 1/2 ton burban xmember from a boneyard for hte disc swap.

What calipers do you guys have them mated to? If you know the piston size of the caliper, post it please. seems they are typically, for the JB5 setup, 1-1/8 rear drum master bore, and 1-37/64 front disc bore. I believe the same front calipers are used with a standard 1-1/8 non-step bore master, but not sure. Thanks!

[Chuck78]

C'mon, anybody have feedback on these?
If the engineers designed it for less drag, that sounds like a great idea, but the one piece cast iron masters will look much better under the hood in my opinion. Are there any quick takeup units that still use the cast iron one piece master/reservoir design?????????? ???

[Super73]

Is this the one you are talking about?





If so, I have used it quite a bit in my truck before it went down. I pulled it off a mid 90's full size (Truck came to me as manual brakes). Worked great stopping the truck from upward of 110mph. Someone had already done a later model disk swap in the front before I bought the truck so I can't tell you exactly the year. But I was using an adjustable master in line of the drums with nothing on the front.

I'm removing the booster to run manual brakes. Suprisingly enough, just putting it around the shop with out the vacum to the booster, it's easy to depress and stops fairly good. I think a lot of that is in the pedal ratio. Also just finished up the rear disk conversion.

[Chuck78]

yep, that's the style. Looking for opinions on how much drag they will save vs the older style, as I hate the look under the hood of a vintage truck, but I love the functionality of the less-drag idea.
Your truck is b@d@$$, Super73. Most people wouldn't expect to see a beat up rusty pickup truck screaming down the 1/4 in 11.2-11.9 seconds!!!! Wow. The monster slicks sorta give it away, but still, the thing is a somewhat unsuspecting rocket... Quite a bit of frame twist on those extra hard launches though, wow! I guess slicks will do that when you throw that much power to the ground!

[hAetWagon]

That's a mean lookin motor.
I'd like to hear more about this here..

[Super73]

Don't want to take away from your thread and question, but there is much more axle wrap than frame twist. Next time out that will be addressed with a large antiroll bar in the rear.

Hoping to go 11.4-11.5 on motor next time and bottom 10's with the N20..


As far as reducing drag via the master, what are peoples reasoning behind it? Is the master allowing fluid to come back easier? I would think there would be just as much to gain with better calipers. But as far as I know, drum offer much less drag than a disk with more stooping power when cold, they just have a tendency to fade once hot. However, with the advancements in large calipers and rotors, this is becoming less and less true.

[TR65]

Hey Chuck,

Other than looks there is not much to recommend the cast steel masters in my mind. With the plastic you can see how much fluid you have, hold more fluid, you can open and add without spilling fluid all over, and of course the whole aluminum master and plastic resevoir is lighter. I run an 87 master with a 71 booster in my 65. Works good. I run a manual proportioning valve and gages to set the pressure split correctly for the non stock combination of front and rear discs.

TR