fast-fill master cylinder?

[TRX]

Is there a fast-fill master cylinder that will fit the G bodies?

I made a pass through the local U-Pull, but all the ones I found pointed up at a fairly steep angle and the reservoirs were made to match that. My '80 Malibu's master cylinder sits closer to level.

It would be nice if it has the same kind of fittings as the Malibu, but I'm willing to modify or change the hard lines if needed.

 

[TRX]

Ah, sometimes it's just a matter of tickling the earch engines properly...

The 1988 S-10 master cylinder looks like it will work. The reservoir is level instead of steeply angled like the F-body cylinder.

The 1980 Malibu cylinder is listed as 15/16 bore, 9/16-18 and 1/2-20 fittings.

The S-10 cylinder is listed the same.

There are three S-10 cylinders: a standard 15/16, a fast-fill with a 1-1/4 step (JB1) and another with a larger 1-7/16 step (JB3). Prices look to run $65-ish for the JB1, $45-ish for the JB3.

GM had at least two mounting bolt centerline widths across the years, but I'm pretty sure the S-10 and G-body will be the same; many bits interchange between the two, anyway.

 

[pontiacgp]

why would you need a fast fill master if you are using the stock set up?

 

[TRX]

I'm not. Or rather, I plan not to.

I have a B-body front brake/spindle setup and a '95 Camaro rear disc setup. I'm gathering up all the miscellaneous bits for the conversion.

The fast-fill master cylinder isn't *necessary*, but GM used a lot of them on cars with rear discs where axle play might cause pad knockback, and I might as well replace the original 1980 master cylinder since I'm changing everything else...

 

[manualbrakes.com]

If you are using a vacuum boosted brake system on your g-body, all of the master cylinders will be at an angle because of the angle of the firewall. The plastic reservoir may flat on top, but the cylinder will be pointing up from the firewall at an angle unless your running an aftermarket manual brake adapter that levels out the master cylinder.

Basically the S10 step bore (fast fill) master cylinder housing is the same as the 1982 and up g-body vacuum boosted step bore master cylinder housing. Most of the power boosted versions of the S10 and 1982 and up g-body step bore master cylinders are the same step bores of 24mm (15/16") pressure bore and 36mm (roughly 1.5") volume bore. The manual brake S-10 step bore (fast fill) master cylinder came with a 24mm pressure bore and a 31.6mm volume bore and was also used on some early power boosted g-body cars.

The step bore design (fast fill) is used for LOW drag calipers which require the extra volume of the larger bore to fill the LOW drag calipers. LOW drag calipers retract away from the rotor more that a normal caliper and require this extra volume to push the brake pads back up against the rotor. The step bore design (fast fill) master cylinder is only used on the front brakes (rear port of master cylinder closest to firewall). Front port that goes to the rear brakes will only use the pressure bore size of 24mm. From my experience, any remanufactured caliper is rebuilt to NON low drag (normal) caliper standards and do not require a step bore master cylinder. Any new calipers, that you can find, are also rebuilt to normal, NON low drag standards.

The other difference between the S10 step bore master cylinder and g-body step bore master cylinder is the reservoir. Since the S10 firewall is flat and the g-body firewall is at an angle, there are two different reservoirs to compensate for the different angle and put both lids of the reservoir flat with the ground. The reservoirs are interchangeable between g-body and S10 master cylinders and most likely b-body step bore master cylinders.

Using a 24mm bore master cylinder with large b-body calipers and vacuum boosted assist will give you super sensitive brakes with no brake feel and very, very, very easy lockup. You will most likely like need to use a b-body master cylinder to use with the b-body brakes to get a good pedal feel and easier modulation for the brakes. If you want to run a step bore (fast fill) the b-body step bores have a 1-1/8" pressure bore and a 40mm volume bore. Match this master cylinder to the b-body booster (see conversion to g-body on the web), b-body front brakes, and you will have more brakes than any tire combination that you can put on your car can handle.

Compared to earlier g-body strait bore (normal) master cylinders (1978-1981), the step bore master cylinders are HUGE in size. All step bore master cylinders came from the factory made in aluminum with a plastic reservoir. ALL new ones are cast iron with plastic reservoirs and as heavy or heavier than the 70s cast iron master cylinders.

Also a booster for an earlier strait bore (normal) master cylinder will not work with a step bore master cylinder as the housing is too large to fit on the earlier booster.

When bleeding step bore master cylinders, I suggest getting a syringe type bleeder to help bleed a step bore master cylinder. The step bore master cylinder has a 100 lbft bypass valve that transitions from the volume bore down to the pressure bore during braking. This bypass valve can hold air and is hard to bleed with the normal bench bleeding procedures. The best way to bench bleed the master cylinder is to use a syringe to push brake fluid back up through the master cylinders outlets up to the reservoir removing the air from the master cylinder's bypass valve. After I use the syringe bleeding process, I then plug the outlets with 1/2-20 inverted flare plugs for the rear port (front brakes) and 9/16-18 inverted flare plugs for the front port (rear brakes) and cycle the master cylinder piston until it is rock hard and does not move more than a 1/16 of an inch. When the piston becomes rock hard and does not move, I hold pressure on the piston of the master cylinder for 45 seconds and see if the pressure holds and the piston does not move. If the piston moves and starts to slowly sink down the bore, you have a bad master cylinder. If find the plug method of bleeding is better than the recirculating hose method because you can test if the master cylinder is good before you bolt it up to the car and bleed the rest of the system.

Hope this helps.

 

[TRX]

Hope this helps.

I think it freakin' rocks! Thanks!

Can you suggest a year/model for an appropriate 1-1/8" B-body cylinder?

 

[manualbrakes.com]

My best friend is rockauto.com for researching parts.

You can search different parts and they have the picture so you can see what you are buying. Some parts numbers for master cylinder list the bore sizes either in the description or in the "info" link.

You most likely can get the b-body vacuum booster and master cylinder from a 1987 Caprice. Double check before you buy to make sure you are getting what you need.

Here is the link for the b-body brake booster install.

http://www.montecarloss.com/community/ubbthreads.php?ubb=showflat&Number=757283&page=1

 

[TRX]

Any new calipers, that you can find, are also rebuilt to normal, NON low drag standards.

Hmm, interesting. I ventured off into google-land and found this bulletin from Allied Signal: https://www.google.com/url?q=http:/...ggoMAA&usg=AFQjCNFQ3Be4Chit--aGJh5T17wGxo5omQ

and this from Master Power: https://www.google.com/url?q=http:/...gguMAE&usg=AFQjCNHGFJX2ma8S5Pl6SDQGkKwngbNyOg

It looks like the O-ring grooves are cut differently depending on what seal the caliper originally was made for. Wonderful...

 

[manualbrakes.com]

Lets talk calipers.

G-bodies came with a D154 "metric" caliper. This caliper was used on 1978-1988 G-bodies, 1982-1992 F-bodies, and 1982-2004 S-10 Trucks and SUVs. Same casting. From 1978-1981, these calipers are considered normal, NON low drag (normal) and used a 24mm strait bore master cylinder for vacuum boosted applications and 7/8" bore master cylinders for manual brake equipped g-bodies. From 1982-1988, on G-bodies, the calipers where considered LOW drag and used the step bore (quick fill) master cylinders that we have been talking about.

On S-10 trucks, from 1982-1997, these came with LOW drag calipers from the factory and used a step bore (quick fill) master cylinder as we discussed above. From 1998-2004, these trucks came with NON low drag (normal) and used a 1.0" strait bore master cylinder.

All third generation f-bodes from 1982-1992 used LOW drag calipers and a step bore (quick fill) master cylinder. These master cylinders differ from the S10 and G-body in that they have the outlets on the passenger side of the master cylinder and have metric bubble flare outlets versus standard inverted flare outlets on the S10 and g-body.

All store bought and online part store calipers are remanufactured (used rebuilt castings) and have the same part number for all years from 1978-2004. I speculate they rebuilt them to NON low drag (normal caliper) standards, if that is possible, because they can be used with a strait bore or step bore master cylinder. A LOW drag caliper cannot be used with a strait bore master cylinder as the brake pedal will sink quickly to the floor when trying to stop. I am uncertain that the caliper bodies were machined differently between LOW drag and NON low drag.

When in doubt, buy new. For the D154 "metric" caliper, AFCO has the only stock replacement NEW caliper under part number 6635003 and 6635004 that I know of. There are also NEW "big bore" versions of the "metric" D154 calipers.

The B-body caliper is the D52 caliper and was used as early as 1968 through 1996. I am less familiar with the D52 caliper as I do not work with them as much. Like the D154 "metric" caliper, these were manufactured as normal, NON low drag calipers (1968-1981) and LOW drag (1982-1996). From what I can tell, most of the remanufactured calipers have the same part number also. So if there are issues with rebuilt calipers, they will be the same as the metric calipers. That being said, I have not had substantial negative feedback on the remanufactured calipers with my customers.

The "metric" D154 and the B-body D52 has A LOT of after market support. Pad selection for both is limitless. The B-body D52 caliper has a huge piston area which equates to the best clamping force of any caliper, that I know of, that you can use. Since 1/2 ton trucks, police cruisers, limos, and taxis use the D52 caliper there are heavy duty pads you can buy that have a different, larger brake friction compound area. If it was not for the perceived bump steer issue, I would highly consider a B-body spindle swap on my g-body. For the money and braking performance, the B-body big brake set up cannot be beat.

 

[TRX]

Thanks again!

Hopefully I can get out to the shop today and see what calipers I have. The brakes, spindles, A-arms, and bits came from a friend's GN; it's old-school from back in the '90s. He was running manual brakes. If I was going turbo I'd do the same, but otherwise I don't see any need to get rid of the servo.