skinny z

I've done a thorough search. There certainly is a lot of info out there, some of it conflicting so...
Seeing as I've upgraded to the LS front brakes (as well as PBR rear dics), I'm thinking the move to a 4th gen master cylinder is in order.
I've found this in another thread:

Not sure of the logic regarding the larger bore but it makes sense to me to use the OEM arrangement. That is: 4th gen calipers and a 4th gen MS.

So my question is: Is the information about the 84-92 brake line fittings being the same as the 98-02 MS fittings correct? I currently have an 86 MS.

I've also got the GM prop valve that Ed Miller sells and plan on replacing my original 3rd gen valve with it.

soarestransam

yes the 4th gen mc will work in our cars u may need to change the flares of the lines and bend them back slighty to make it work but it will work just as fine as the 1Le master u have in the car now

skinny z

Thanks for that however my question remains:
I'd like to know ahead of time if I'll have to get new fittings haead of time.
And to what style, if there's a difference.

RBob

iTrader: (1)

LS1 brakes:

Camaro/Firebird (98-02)

M/C:

RH ports
Bore Size: 1"
Rod Cup: dimple
Front port Size: M12 x 1 bubble flare
Rear port Size: M11 x 1.5 bubble flare

RBob.

Orr89RocZ

iTrader: (20)

I did not change fitting size on my car. 89 originally, just put the 4th gen setup in. Went in fine. Had to slightly bend the line to get it to line up due to using hydroboost instead of vacuum booster

skinny z

I pulled this Luke Skaff's website.





Notes:
(1) 82-83 F-body master cylinders have a different thread and fitting then the later years F-bodies. It gets very confusing which master cylinder is used on which car from 84-92 F-body, the parts list from each manufacture list different years and different applications. From my research it appears the 18030556 part was only used on the 84-88 cars with rear disc brake and 18030555 was used on 84-88 cars with rear drum brakes. It also looks like from 89-92 GM used the smaller drum brake master cylinder 18030555 on all f-bodies.


I suppose what this ultimately means (despite other people's experiences) is that it's entirely likely that I'll have to change one line, possibly both or neither. What I have to do now is get a replacement master cylinder and go from there.
The whole point of this excercise is that I'm finding an unusual amount of pedal travel although the end result is excellent braking otherwise. I'd expect any braking action to be inititated immediately upon pressing the pedal. Perhaps with the larger volume of the LS calipers, there's insufficient volume being supplied by the 3rd gen master. I also think (but aren't entirley certain) that it may be a disc/drum master. It's been a long time since I did the original disc swap on the rear (from a 10 bolt drum to a 9 bolt with Delco calipers) that I've forgotten. Now I've got the D44 rear with the PBR calipers.

J.C. Denton

iTrader: (1)

Does it make sense to swap the 98-02 Master with the stock front discs and rear drums (92 Firebird)?

I hate bleeding brakes with the 3rd Gen rectangular brake reservoir. The 4th Gen style will make this a lot easier cause I can use a pressure bleeder. Or is the reservoir tank exchangeable without mods on the 3rd Gen Master?

Greetings!

Dfdub92

I won't to use a 4th gen mc because I can't get the power bleeder to seal...I want to be able to use the screw on cap where I know it will seal. Can someone post some pic of the two mc side by side are will the 4th gen bolt right on. Is it the whole mc are just the reservoir?

Dfdub92

pics please of the master cylinder swap.

1986 I-Roc

Please update me on this. I am having some issues with my braking after upgrading my brakes. I had rear drums and have upgraded to discs and the rear and then also upgraded to the LS1 brakes in the front. Now I have no braking power at low RPM's. I am wondering if the factory original MC and booster need to be upgraded as well and if so what the right option would be...any help would be greatly appreciated as I spent a lot of money upgrading my brakes and now they are worse...much worse

QwkTrip

iTrader: (22)

You don't want a 4th gen master cylinder. There will be a significant gap between the master cylinder and the stock 3rd gen booster pin that causes a dead pedal near the top of travel, and long pedal throw. Nothing wrong a 3rd gen master cylinder. It's not an upgrade to switch to a different 1-inch bore master cylinder, just money lost out of your pocket.

If your pedal sinks then there is air in the system.

skinny z

From the list posted above, the only MC with a 1" bore (speaking of the fronts) is the 4th gen version. Any 3rd gen MC in the list has a minimum 1.25" bore and possibly as large as 1.42". Wouldn't that then mean that less pressure needs to be applied via a 1" piston vs an 1.25" piston for the same result at the caliper? I think I understand Pascal. This may relate to the question just asked and a possible remedy. The relationship between the booster and MC would need to be addressed although I haven't any direct experience with that.

In all likelihood, yes. Bleeding brakes is one of those things that either goes very well and becomes a royal pain in the butt.

QwkTrip

iTrader: (22)

The stock 3rd gen master cylinder has a stepped bore, but it's the smaller 24 mm bore that is used for actual braking.

The high-pressure primary piston (front brakes) and secondary piston (rear brakes) are inside a 24 mm bore, or just about a 1 inch bore diameter. The 1.25 inch diameter stepped portion is only for the quick takeup feature, and that feature is out of the picture when brake line pressure goes above ~100 psi, so it's not a factor for braking calculations.

Basically there are 3 pistons. The quick takeup piston first pushes a high-volume, low-pressure shot of fluid at the back side of the primary piston. That shot of fluid collapses the cup seal of the primary piston and the fluid passes through to the front brakes to "quickly take up" the gap between brake pad and rotor. The quick takeup relief valve opens at about 100 psi and the rest of the fluid inside the 1.25" bore chamber gets bypassed to the reservoir. After that is when the real braking occurs. The primary piston cup seal [noun] seals [verb] again, and the master cylinder starts to generate high pressure for braking.

This stuff is like one of the great hidden mysteries of the 3rd gen world for some reason. That and don't use a 4th gen master cylinder.

skinny z

Seems that you have applied the same precise analysis of the master cylinder as you did the proportioning valve. All very educational. Thanks for both.
In an odd way, and I'm not sure how it managed to come about, but after I posted this original thread in 2015 regarding a less than satisfactory brake apply (the rears mostly as the fronts were OK), the rears have come into their own. Previous tests would barely slow the tires down when on jacks. A revisit to that after replacing a wiped out axle bearing showed them working superbly. I had done nothing other than drive it.
Another 3rd gen mystery.

ShiftyCapone

iTrader: (7)

The only exception being if you run an aftermarket master cylinder. They supply spacers to take up that distance and can be confirmed with a tool they sell. As QWK mentions there is no reason to switch. I did for aesthetics only and the 4th gen unit is a little cleaner looking.

WildCard600

the reservoir setup with the screw on cap instead of that garbage snap on flat lid is the main reason i'm switching to a 4th gen unit, the looks are just a bonus. Paired with a 4th gen booster there isn't any issues with booster pin distances as far as I am aware. Mine are still sitting on the shelf waiting for the crate engine to go in however.

QwkTrip

iTrader: (22)

Nope, I did a Google search and watched a training video yesterday. LOL!
Had some great pictures with cross-cut view and explanation.

rgauder

iTrader: (1)

Can you switch just the reservoir?

QwkTrip

iTrader: (22)

Nope

JR92RS

deleted question

JR92RS

deleted response