Help me identify this Master cylinder

[74 Bronco Billy]

I purchased this master cylinder from Wild Horses 4x4 at a swap meet, there was a tag that said it had been bench bled. I took it apart, hand it powder coated, then reassembled. I think there might have been some sand blasting particles left behind that have ruined the rubber parts inside as I can get any pressure to develop now. So, what make / model car or vehicle did this master cylinder come out of? I need to get the rebuild parts for it, I'll probably just go down to Napa (I like to support the locals), but it be nice not to have to haul everything down there, but to just call and ask for the right rebuild kit to be there.

Dang if I know what year model it is, do you? And Yes, I did make all my own stainless steel lines and hoses for both the brake MC and HB. Lot of work there.

Thanks,

Forrest

 

[toddz69]

That's a CPP master cylinder that's based on the old cast-iron GM units - most resemble the 77-82 Corvette units. However, these units have fittings on both sides for a fairly universal/wide-ranging fitment and it looks like you're using 3/8" tube nuts on both lines? I don't think there was ever a factory application made like this master so you're likely stuck ordering another one from WH, CPP, or other vendors who probably sell it as well. Should be a 1.125" bore master.

Todd Z.

 

[Madgyver]

looks like a 77 corvette master cylinder.

 

[DirtDonk]

Todd is correct. However some of the rebuild parts are probably standard, such as fitting a 1.125" bore. But I would not take that as etched in stone until you verify that the parts you purchase locally are the same as what you took out.
You did keep the old stuff I hope, correct?

As you've found out, powder coating a master cylinder is a finicky operation and not to be done casually. As with a few other items, keeping any cleaning materials (sand/media) out of the internals is critical. Tape and power towels don't cut it. If you or they did not, you would want to plug the ports with metal port plugs, cap off the rear piston opening and top cover opening extremely tightly and with stout materials.
I doubt that the coating process of heating to near 400° causes any problems, but not really sure if it could effect the bore shape or not. Never tried it...
But visually from your results anyway, it comes out looking fantastic!

As Todd mentioned, with the ports are on both sides and the mounting holes elongated to fit multiple types of braking systems, it's not from any specific older model vehicle application. We used to stock two different masters, one for standard and vacuum boosted brakes, and another for hydro-boost applications. A few years ago we went with this long-hole design which saved a lot of hassle. All new product, and as said, not specific to any older application. But none of that should effect internal parts, as the functions stayed the same.
However I just don't now if CPP or MPB have their own proprietary piston and internal parts designs, different from the old Bendix products. I would hope not, just to make it easier/cheaper to obtain parts, but don't know.
Never had to rebuild one yet!

Got pics of all the stuff you pulled out of it? Or is it still installed on the vehicle?
Maybe we'll get lucky and a member or two here have had theirs apart for refurbishing after many years of service and know for sure what to look for.

Paul

 

[74 Bronco Billy]

Thanks for the quick replies. Nuts!! Nice history lesson Paul and Todd, I guess I'm gonna call WH to see if they know (yes Paul, I know you're probably working from Home), it that doesn't work, than it is remove it and pull apart and see if Napa has the parts. ugh.

 

[Apogee]

What's the depth of the pushrod hole on that CPP unit? I only ask, because the internals are the same as the C3 Corvette if I'm not mistaken, but there are two versions; 1968-1976 with a deep pushrod hole and 1977-1982 with a shallow hole, so if you do find a rebuild kit, make sure it matches what you have so it'll work with the output rod on your Hydroboost. Master cylinder rebuild kits used to be readily available, however not so much anymore from what I've seen, so it's probably easier (and possibly cheaper) to just replace it...they're $59 at Summit Racing, minus the powdercoat of course.

 

[DirtDonk]

The master comes with a deep well piston and a bullet shaped spacer to fill it up for power brake systems with short push rods.

 

[74 Bronco Billy]

So the rebuild kit was 60.00 at O'Reiley, but the needs to be .480" diameter, not .530" like original. Ack. Anyone know where to get a smaller "bullet"?

Sent from my SM-G955U using Tapatalk

 

[DirtDonk]

So the rear facing openings in the piston are smaller even though the piston is the same size internally? Can you drill out the hole without damaging the piston?
A smaller diameter pin of similar shape and size could be maybe from McMaster/Carr? Grainger maybe?

Paul

 

[74 Bronco Billy]

Hi Paul,
I just finished talking with Summit, no dice. We came up with the name push rod spacer or pushrod pin. Ugh. I think drilling it out will not work since the diameter of the barbell is smaller, wouldn't want it to fail due to lack of thickness at that part. Grr.

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[DirtDonk]

What are the chances you could make a spacer? Seems like you could take some half inch rod and grind it down a little bit and then create a tip on one end in a divot in the other.
You might even find some strange piece that’s the right diameter and all you have to do is create the appropriate ends.

Just a thought.

 

[74 Bronco Billy]

What are the chances you could make a spacer? Seems like you could take some half inch rod and grind it down a little bit and then create a tip on one end in a divot in the other.
You might even find some strange piece that’s the right diameter and all you have to do is create the appropriate ends.

Just a thought.

Thanks for the encouragement Paul, this project is going on 5.5 yrs and just gets to be so frustrating at times. I’d really like to be able to drive it. Ugh. I may try to remove the spring off original barbell and put new spring and rubbers on it. Really frustrating that WH does not carry a rebuild kit for their MC kit they sell / sold. Rrr. I shall persevere.

 

[DirtDonk]

It’s not a bad suggestion. I’ll look into it. As far as I know it’s the first time it’s come up, but I’m sure it won’t be the last since they’ve been around for many years now.

That was pretty spendy for a rebuild kit too I must say! I think the last one I bought was under $10!
But there I go dating myself again…