The Stovebolt Site Forums The Parking Lot Big Bolts Brake upgrade

Not to rehash old stuff, but couldn't find quite what I'm looking for...
I just got an excellent condition 1952 Chevy firebolt, being in Canada it's a model 1700, making it a 3 ton.
MC leaks at pushrod end, unsure of hydrovac condition.
Brakes at wheels all look excellent.
How hard to repair MC and hydrovac (if needed), or am I better off going new (what parts... 3ton not listed most places), or even is there a two circuit system I could put in?

Here is some reading on the hydrovac.
http://www.stovebolt.com/techtips/bendix/erickson/
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=526858

I recently cleaned up the master cylinder on my 1 ton and installed a new kit, that's not usually very difficult.
https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1135231/Grigg.html#Post1135250

Here is some info on possible dual circuit MC upgrade.
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=720292
https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=973790

Hy 52vff, welcome, your master cylinder has a bore of 1 1/4" Raybestos MC9220 at RockAuto $119.67 this is a new master cylinder
at Napa their p/n NMC P9220 $119 this is a remanufactured master cylinder, NMC M9220 $199 this is a new master cylinder. As Grigg said you could disassemble your master cylinder and put a kit in it if the bore is not too pitted, if your brakes work now but you have a leak at the pushrod end of the master cylinder your master cylinder should be rebuildable. as to the Hydrovac Geoff at Alreta should be able to help with parts or a rebuilt unit, hope that helps.

Thanks 3B and Grigg.
I got truck in running condition, but no brakesm even park brake worn out. Rear looks to be recently redone, front no signs of leaks and lots of shoe left. MC was empty and cap seized, brake June from it to hydrovac replaced.
My first debate is changing to a dual circuit... problem there is first what to use, need 17500lb ability to match chassis. But to complicate things, in this firebolt at least, the MC is reverse mounted to allow a second clutch linkage from the pump,greatly reducing area to work in. Don't really want to need two boosters , one per circuit.
So then if I stay original.. without tearing mine apart can I tell bore size as no tags or cast numbers are on it (to get proper rebuild kit), is an 1 1/4 bore the largest offered? 3B the Napa one has mounts wrong side (assuming they're the bolt bosses in puck not outlets), both talk of two outlets. Mine only has one at the end opposite the pushrod.

My GMC 630 has 1.5" master, got kit on EBay, waiting for warmer weather to R&R MC.

Ed

Hy 52vff,When I checked the part description at Napa it said the master cylinder had two mounting holes and one port. The mounting holes go right through the master cylinder and the single port opposite the pushrod is a 7/16"X24t.p.i., this is the correct master cylinder for your truck, hope that clarifies/helps.

Thanks guys. Think I'll b pulling the MC tomorrow. Also park brake shoe assembly. Hoping to get shoes relined, see about takin MC apart to verify bore. Then I'll decide rebuild or replace. Think I've pretty much given up on upgrade to dual circuit, at least for now.

So I finally got MC off and takin apart. It is 1.25" bore, not 1.5. Pitting not too bad but has caused some rougher areas. Rebuildable but probably should be sleeved. Have a place about an hour from here that can do it for $275. Going to check price at NAPA ( Canada's online one won't put $ up) tomorrow for new / rebuilt.
Thanks everyone, I'll post what I find out..

That is a whole lot of money for sleeving a MC, shop around.
I recently put a kit in my MC (all it needed) and figured if necessary I could sleeve it or could have it done for about same cost as NAPA wanted for a new MC. Given choice of new or with stainless steel sleeve I'd choose sleeve even if it came at a slightly higher cost.

Grigg

I am sort of thinking about the dual master cylinder system for added safety. There has been a lot of discussion online here. I found a page that had some typical brake set ups. I would be interested in doing the first one, drum/drum. Does that diagram look like a correct set up?
http://www.mbmbrakeboosters.com/ind...y&layout=blog&id=8&Itemid=16
Also, the master cylinder that RDomec looks like it would fit in quite nicely on my 1948 two ton.
http://s1006.photobucket.com/user/r...c%20Brake%20Conversion/100_4114.jpg.html
If the dual MC has a brake booster, I take it you wouldn't need the hydrovac?

Hy Super55, I like the system drawings you linked but I find the Domec pictures to be too small. I assume his bracket will move the booster/master cylinder towards the rear of the truck and down below the centerline of the frame this will allow the system to be installed where there is more room for it.

NAPA wants $280 for new MC. +$500 for hydrovac rebuild...

Okay I've read bunches of posts and online.. still hasn't answered all my question. RDomec's conversion is what I think I'm gonna go for, but would a 1 tons MC and a 3/4 toms booster really be right??? By just using 10lb residual valve I can use a disc MC for drums?

I was thinking a 8inch vacuum booster and a c5500's MC would be better sized?? Are boostersspecific to MC's? Or just as long pushrod works and they bolt up?
Boy am I a newb on this.

Hy 52vff, please don't use abbreviations in your posts it confuses some people. The critical thing is the bore of the master cylinder, do not go smaller than the bore size of the original master cylinder, in this case 1.25". Yes you can use a master cylinder designed disc brakes for drum brakes by installing 10 p.s.i.residual pressure valves in each circuit. The introduction of "hotrod" parts availability has confused the issue of what is correct and adequate for a modified brake system, there are so many different ways to go and a lot of incorrect information is floating around out there. If you find a system that you want to purchase please describe it to us first and get our opinion, hope that helps

OK. So what I'm thinking is getting a drum / drum master cylinder for an early 80‘s GM c4500, pretty sure they're also 1.25 inch bore, but definitely similar chassis weight. Pair it with a hydrovac hopefully made for the 4500's as well. Mount the whole thing similar to how bdomec did.

Hy 52vff, Hydrovac is a booster installed after the master cylinder essentially a "slave" of the master cylinder, todays systems whether vacuum boosted or hydraulically boosted "Hydroboost" apply their boost at the input of the master cylinder. The "new" systems only require one booster to boost both the primary and secondary systems.

Im confused. I understand the hydrovac to be a vacuum operated booster. Old school - whats in my 52 comes with slave cylinder and goes after the master cylinder. New type goes between pedal and master cylinder. Hydroboost is a hydraulic oil run booster typically also between master and pedal powered by typically the power steering pump?
Im looking for a vacuum unit since I don't have power steering, but prefer only one unit "New" style.
Am I off on terminology?

A Hydrovac unit is a vacuum booster that is mounted on the frame and the assist part is activated by the brake line hydraulic pressure. These units are very common on the single pot MC systems. What your talking about is a modern power brake booster that is mechanically linked to the brake pedal and has the MC bolted to it (these units are not call Hydrovac units) and they are very common on dual pot MC systems.

No matter what type system you install you need to use the same bore size as the original MC had, otherwise you won't move enough fluid out into the system.

Hope this helps,

Mike B

OK so I got a price at NAPA for master cylinder of nearly $300. Been talking to MBM brakes and they're recommending a dual chamber 1.25" bore master (MC36352H) and a dual chamber 9" vacuum booster (pb9513). I'd have to custom mount this, but it seems workable. Any thoughts?
Super55 that's right about the booster, in fact you can use a dual master cylinder, and two hydrovac's if you wanted to though.

Thanks

OK, I just talked to my NAPA guy about the 1.25" bore MC and this stuff is not as expensive as you're being told.

Part number M9220 is a new master cylinder that list for $319 and walk in customer pricing would be about $210.

Part number P9220 for a remanufactured master cylinder sells for ~$120 and the core charge is ~$20

Part number 33 is the rebuild kit for ~$25

As i may have mentioned earlier I just used the kit but the remanufactured cylinder seemed well priced if it was necessary. I'd also first look into having your own old cylinder sleeved (locally or elsewhere) with stainless steel and buy just the $25 kit. This might be less expensive than the remanufactured cylinder and will be the better longer lasting solution.

As for the modern dual circuit stuff sounds like you have good info and ideas on those options.

Grigg

Grigg - $210 in the US would be "nearly $300" in Canada

Bill

Oh... there is that. It's been a while that I checked exchange rates, thought they were still hovering around equal...

Anyhow, I did find some part numbers that could be helpful to others, and the rebuilt option is cheaper than what 52vff had found already.

Thanks,
Grigg