Pirate Jack booster died in '68 - would a late B-body booster fit?

[cudak888]

Hello all:

In good old "there goes the aftermarket" fashion, the relatively new 8" dual diaphragm Pirate Jack booster that I installed on my '68 Satellite bit the dust last weekend - it's sucking manifold vacuum through the rear seal. Brake feel is about 75% of what it used to be.

For the record, this is the setup. The car used to be drum/drum, but if you have to think of my question in terms of the overall setup, just think of it as a factory disc/drum car now. All of the correct parts are there - firewall plate, Z-bar, hold off valve.

Also note that the PJ master cylinder was junk as well (wouldn't bench bleed correctly), so I'm running an appropriate Cardone unit instead:

Since there's been no reply from PJ (none from when I inquired about a very minor hiss at the back of the booster months before it failed entirely) and I don't expect anything else out of them, I'm studying my options.

I know the PJ booster is also sold by a few other distributors (for $250 - $300 clams!), and frankly, I'm not interested in anything that looks like it's the same thing that failed quick on me before.

I know there are the oddball wannabe Hemi-type boosters mounted on risers out there, but I'm rather interested in the idea of something that A. Isn't priced ridiculously and B. Could be had at a parts store. So I've been snooping around on Rock Auto looking for interesting fixes. Interesting in terms of "it's cheap" and "Hey, look, I found a workable combination that nobody thought of yet."

Thus, I've been wondering whether a simple 1976+ B-body single-diaphragm booster like this one would work, but there's two things I don't know: Is the firewall bolt pattern the same as the pre-1974 cars? And if it is, is the diameter larger than 8"? I know one of the limiting factors on the '68 is the inner apron.

The way I see it, single-diaphragm shouldn't be an issue; after all, I'm running the same 11.75" brakes up front as an M-body, which had a very similar booster (far as I can see, the major difference is the more common two MC studs vs. the Mopar four). I also have the PJ bellcrank already installed, so I've got that end sorted - but there's the issue of whether the rod at the back of the booster is big enough...

I've also considered this from an '80 Newport (R-body), which uses the two-bolt master type - but I have a few Ford masters kicking around which I could probably adapt.

Any advice?

-Kurt

 

[Malicious]

Subscribed. I think my has started pulling in air too. Only noticed since I hooked up a Vac pump to get better braking. I have an original Bendix booster here. Just don't know if its any good.

Not looking forward to replacing it if its needed.

 

[cudak888]

Subscribed. I think my has started pulling in air too. Only noticed since I hooked up a Vac pump to get better braking. I have an original Bendix booster here. Just don't know if its any good.

Not looking forward to replacing it if its needed.

I've been busy in the meantime, so I think I can answer a few questions on this one, and also document a few things here (like I did with the stickied firewall plate post) so everyone is clear on ALL the options and my quandary. Maybe some of you Mopar gurus of many years know all of this by heart, but some of us can do with a clear guidebook that saves hours of thread searching.

*********

The following are the present-day options for '68/9 disc boosters:

1.
First is the Bendix 8" reproduction (I believe it's a '68 copy and differs from '69, someone fill me in) as sold and branded by Pirate Jack, A-Team Performance, Summit Racing MBM Brakes, and a few other vendors, both with and without MC's:

Dorman also lists rebuilds of this Bendix-style booster (will put P/N here once I can find it again), and parts stores will list it, but they are not available at all. You'll hit a dead end when you try to special-order these; they have none in stock for rebuilding.

As for my project, I've decided that the failure of my virtually new unit is enough for me - forget this one.

2.
Next up is the 8" booster sold under The Right Stuff name as RPB8001 in cadmimum gold, and RPB8001C in chrome. By default, it comes with the 426 HEMI offset booster and Z-bar (see the addendum at the end of the list about the HEMI bracket).

Functionally, this is the same as the Bendix, but visually, it is almost identical to some Ford boosters (same as a '67 Ranchero, as one forum member noted), but they've been modified with the Mopar 4-bolt master cylinder pattern in front, and the wide 4-bolt Mopar firewall pattern.

Summit Racing's reviews of this booster speaks for itself, it's junk too!

3.
Then there's this 8" booster, which I'm certain is nothing more than a GM booster with zero modifications. It's offered for Mopars in five gazillion forms, but if you search close enough, you'll find that Pirate Jack and MBM Brakes lists them as PB8531 (PB8531C for chrome). MBM Brakes states "Great for installs on GM A, F, X Body Cars" and notes that they "will work on a variety of GM, Ford, Trucks, & Passenger Cars."

Pirate Jack offers this exact booster with the HEMI bracket and a Wilwood master as a Mopar combo, as the "260-8555-P~PB8531C~BPRP6570~PV2CK-2W." These are the master, booster, HEMI bracket, and proportioning valve part numbers, respectively:

It can be bought in black, cadmimum gold, chrome, and the amount of master cylinders I've seen with it run the gamut - one seller even offers it with a Wilwood master.

CPP's 6374BB2-8D:

A black version is sold by Pirate Jack (competing with the Bendix-repop style, apparently) as the MP-401:

MBM sells this variant as the MP-320 with a GM-style master:

And if you keep going, you'll find ENDLESS variations on this one booster and all the masters it can be had with.

If anything, this is just a bog-stock GM 8" master that you can throw on a Mopar, and I bet those Chevy master cylinders make the brake lines barely clear the inner fenders. They're all over the place. Couldn't find a review on Summit, but there were some on Amazon here that seemed favorable when used in GM applications: https://www.amazon.com/Diaphragm-Po...8-3&keywords=8"+brake+booster#customerReviews

4.
There's another very similar booster by MBM, the PBUP6570/MP-200. Again no idea about this one. Also a GM-style master, probably just another generic 8" GM booster too.

(Continued in next post)

 

[cudak888]

A few footnotes:

A.
Many of you may have seen this offset bracket on new booster/MC kits (and it's in a few of the photos above). These replicate the same offset bracket and external Z-bar used with HEMI cars to clear the 426's valve cover:

Functionally, boosters mounted on these brackets are the same as an 8" Bendix mounted directly to the firewall, just perched on the offset bracket. If you delete the bracket, you should be able to install one of these directly to the firewall provided the booster has the right bolt pattern and if you have a factory under-dash Z-bar. No idea if the Ranchero-style booster is designed as such.

B.
Also, just to be clear, the following is a Midland-Ross style power drum/drum booster. It looks like the Bendix disc/drum 8" booster, but it's not. Easy to spot with the clamp band holding it together. It's available everywhere as a rebuild, and from what I've read, it will not provide the necessary vacuum to operate a disc system (inquiring minds want to know "why?"):

 

[cudak888]

And finally: As for my own car and "let's find a different booster that fits" ideas, I found two snags:

First off, the later boosters don't appear to have the large rod end that accept the Z-bar pivot. Unless there's a sleeve on the Z-bar and I forgot about it. Anyway, I have something against removing material off rods that connect to my brake pedal, so that's out.

Until tonight, I really thought I was left with either the Ranchero booster or the Bendix repop, but I finally made sense of the GM style booster. Yea, the reviews seem OK, but I really don't know 100% if the bolt pattern is the same as the Mopar firewall, because I'd remove it from the HEMI offset bracket and use the Pirate Jack reproduction, under-dash Z-bar. Also, I don't know if the adjustable eyelet on these will work with the repop Z-bar.

There is one other option: Booster Dewey, who should be able to take one of these brand-new, shitty reproductions, and rebuild them with some quality rubber (at least, that's what I've heard, and such niche work only gets a good rep by doing a good job). But that sends the cost of this whole project through the roof, and it doesn't make sense for my 4-door driver-quality beater.

This said, since I have all the barely-used parts from my previous setup still kicking around, I'm going right back to manual brakes. Frankly, after getting used to the high position of a Mopar with a manual brake pedal, I've come to dislike how low the factory power brake system sits to the floor, not to mention how short the travel is.

I ripped apart the dash this evening and will pull the booster and firewall plate over the coming weekday evenings. Should be back up and running with manual brakes by the weekend.

-Kurt

 

[cudak888]

Some pictures from this afternoon:

Yes, you're pretty much obligated to rip apart the whole dash just to get to the upper firewall plate bolts - and the one on the top right (from the back of the booster if power, reinforcement plate if manual) is so impossible to get to that I did NOT reinstall the nut, even though that's usually a no-no for me. Two hours of trying was enough...

Pirate Jack repop under-dash power linkage. I keep calling it a Z-bar, but I don't think that's correct. Some seem to call it a bellcrank, but that it isn't either.

At any rate, it seems to provide very minimal multiplication - if I had to guess by eyeballing the length, maybe 1:1.3. To be honest, it looks to me like it was designed offset to accommodate the existing eyelet of manual brake cars; the whole linkage is an adaptation for the necessary room required for power brakes.

Some more from under the hood:

-Kurt

 

[Pistol Pete]

That one nut is a bitch, no doubt, but it can be done without tearing into the dash. It takes a 1/4" drive universal and removal of the drivers seat. If you're really ambitious, removing the steering column makes things easier as well.

 

[cudak888]

That one nut is a bitch, no doubt, but it can be done without tearing into the dash. It takes a 1/4" drive universal and removal of the drivers seat. If you're really ambitious, removing the steering column makes things easier as well.

I can see where it's easy with the column removed. With it in though...not fun.

I've got to drop my column someday to figure out why the detents in the shifter linkage are sloppy, but not this time around...

-Kurt

 

[cudak888]

Got the ENTIRE thing swapped back to the old parts in record time - just over two hours to get everything out and swapped over. That's not including brake bleeding (PITA to need two bodies for that) or finding the second nut to reinstall the brake light switch - I had to omit one during the previous setup, and I don't know where I put it.

The booster and the way-too-nice-and-clean master:

Manual 15/16" bore disc/drum booster is back home:

No more power brake linkage - straight rod to the manual booster:

Good old fashioned Mopar manual brake pedal, high up in the sky...

Turns out the rubber boot on the rear of the booster did come off, which probably accounted for some of the hissing, but the felt behind it is also pretty ragged. It looks pretty cheap too. More pics of that later.

-Kurt

 

[cudak888]

Ok, booster picture time. Just in case anyone isn't 100% clear, this is the 8" Bendix reproduction.

Here's where the boot popped off. Since I enlarged the firewall hole as per the instructions of this particular booster, it couldn't have hung up on it, yet it appears pinched. Perhaps the rubber got hung up on the equally narrow pedal bracket?

At any rate, this isn't an ideal design. At the least, this boot should be designed so it can be strapped tight onto its seal. It barely takes ANY effort to pop it off, even if re-seated properly.

Also looks like the inside of this thing is made of a cheap PVC pipe and some felt. Meh.

In other news, I got hung up bleeding the brakes this evening due to a bleeder screw rounding off. I went to replace it with a spare - and got a spray of brake fluid in the wheelwell when I opened it.

After scratching my head a bit, I realized the spare came off this same brake caliper when I first got it - some idiot let it go past QC without the necessary bleeder hole at the BOTTOM of the screw. There's NO hole around the bottom at all.

Not going to fart around with these anymore; just going to get some one-person bleeders and be done with it.

And in a passing note, I can't help but be amused every time I turn this guy to full lock. I have a pair of Firm Feel upper control arms on it, but they turned out to be some one-offs they made for a race-spec E-body (eBay find, NOS). Not only do I have 6 degrees of caster, check out the positively modern amount of camber at full lock. FMJ spindles, FYI.

Now I can pull out the "because race car" phrase with this highway-geared pig iron.

I also have the fast-ratio Challenger T/A pitman and C-body idler installed. This thing should be a handling riot, but the factory steering box slop ruins the experience. I've been a cheapskate about ordering a Firm Feel steering box for this car, and I pay the price for it (well, I'd be paying the price for the FFI box too + the additional 50 for having it built with the extra Challenger T/A limit stops so I stop rubbing the frame at full lock, but that's another story).

-Kurt

 

[Malicious]

So the rubber boot is tore at that point? or it just slides off? Would some RTV sealant and holding the boot in place solve your leak problem?

 

[cudak888]

So the rubber boot is tore at that point? or it just slides off? Would some RTV sealant and holding the boot in place solve your leak problem?

No damage, but just slides off. Some RTV and a thin zip tie would probably do the trick, but I'm not putting it back on the car. Less crap to go wrong.

Going to throw it on eBay and cut my losses.

-Kurt

 

[Malicious]

I'm about to start chasing down a hsss I can hear under that dash this/next week. I think it might be what you've described, so RTV and zip tie might save me tearing it out.

Having said that, if it does have to come out, I think I'm just going to ditch the vac booster and go hydro.

 

[cudak888]

I'm about to start chasing down a hsss I can hear under that dash this/next week. I think it might be what you've described, so RTV and zip tie might save me tearing it out.

Having said that, if it does have to come out, I think I'm just going to ditch the vac booster and go hydro.

Sorry to burst your bubble on this one, but the fit between the pedal bracket is WAY too tight to fix the boot. The only way to do it right is to remove the booster:

Honestly, if it wasn't for the HEMI bracket relocating the MC/booster combo far up off the firewall, it's pretty nice to have: No trips under the dash ever again for booster issues. Been looking at some pictures too, and it doesn't look that bad when paired with an RB. Haven't seen an engine bay with an LA and a raised booster yet though.

I know Jonathan Ward (ICON4x4) swears by the current Hydroboost units, but I've had one troublesome one in a '78 Lincoln before. Those units were also a bit overboosted, but Ward says the latest ones are excellent. Not sure which unit he's using.

I considered Hydroboost as well - I already have a Hydroboost-plumbed power steering reservoir from the Lincoln that would slide right onto the Saginaw pump already on the car, but I have no interest in shelling out close to a grand for a Hydroboost unit that barely differs from a junkyard unit except for the mounting plate.

-Kurt

 

[roadrunnerh]

You're a Mopar soldier! I have been spending time under/behind my dash on my 68 RR removing stuff and replacing. My back paid a price...

 

[Malicious]

Bugger, I still see if I can identify it at least. Not looking forward to the job when I need to get on it.

 

[cudak888]

Bugger, I still see if I can identify it at least. Not looking forward to the job when I need to get on it.

Super easy to ID it. Start the car, close the door, shove your head under the dash, press the brakes.

If you have straight pipes and can't hear the leak...you don't have a problem

-Kurt

 

[Malicious]

Super easy to ID it. Start the car, close the door, shove your head under the dash, press the brakes.

If you have straight pipes and can't hear the leak...you don't have a problem

-Kurt

HAHA thats my problem! I have a electric vac pump though as the brakes didn't feel great, so I can test it with that on only.

 

[cudak888]

HAHA thats my problem! I have a electric vac pump though as the brakes didn't feel great, so I can test it with that on only.

Sounds like you've got enough of a lumpy camshaft to warrant the hydroboost. Not just because of manifold vacuum, but to stop your little old freight train...

-Kurt

 

[cudak888]

You're a Mopar soldier! I have been spending time under/behind my dash on my 68 RR removing stuff and replacing. My back paid a price...

Definitely not that much fun; have been in a few old things where access behind the dash is much better. But for my '71 Mustang, I've got to drop the steering column just to replace the shot ignition switch

-Kurt