Power master to vacuum conversion question.

I've decided that my power master brake system is getting too expensive and dangerous. I want to convert it to the vacuum system. I see Gbodyparts and Kirban sells the kits. Kirban's is much more expensive. Is it better? Anyone else these sells these kits? Thanks.
^^^This is probably the easiest and cost effective solution for those looking for an all-in-one kit without the hassle of sourcing your own parts Buick Grand National Vacuum Brake Powermaster Conversino kit - COMPLETE! | eBay

The Gbodyparts kit has a different booster and more importantly requires welding on a new pin to your existing brake pedal (if I remember correctly). Kirban gives 2 options - one includes a brake pedal with the correct pin placement or the cheaper kit that does not include the pedal but you have to weld on a new pin to our existing pedal.

The Earl Brown kit linked above allows use of your existing pedal (still have to drill a new hole for the new pin though) and requires no welding, which is convenient for those who don't weld. The other difference is the vacuum line tee's into the PCV hose whereas the other kits mentioned provides a new vacuum block with a dedicated port to run to your brake booster.
I don't send the vacuum block because they're all leaky pieces of crap. Not to mention cars with flattened stock body bushing will let the EXPENSIVE hood liner get torn up by the ridges on top of the block. (on a personal note, I hate the hose running across the DS valve cover. That's the only one that's easy to remove, and I hate the idea of adding a step on the few things easy to work on. lol)

Another big difference with my kit is the pin since most driveway mechanics don't weld. Mine just requires a drill and a hammer
The main difference in real world use is safety and strength.
I send out a forged clevis pin that's designed to be used in sheer for industrial applications. In a serious ''oh shit'' situation, you'll break the seat tracks before you can even bend my pins. And a bent pin won't take out your brakes. A failed weld snapping off the pedal would make for a bad day (and a dead Buick). My install doesn't have such stress risers to cause a sudden failure.
Everybody else that has new pins look like plain ole mild steel. With the leverage ratios of stock pedals, that pin can see thousands of PSI of sheer if/when things get real.

Oh yeah, I can also send a threaded barbed fitting for those that one to tap the plenum/spacer/intake for the vacuum signal. But, for all the kits I've made I've only had ONE person choose that route. So I hardly ever mention that anymore. lol
When I had my manifold off for porting, basting, and painting, I deleted the EGR boss inside the manifold, welded a plate over the hole in the floor, drilled a 11/32 hole in it, welded up the EGR boss, and drilled and tapped a 1/4 pipe thread into it on the port to the inside if the manifold. The lower port connects to the exhaust crossover. I welded those shut too at the manifold flange. A 3/8" hose barb allows a straight shot with a short hose to the booster. It looks clean and factory!
I've decided that my power master brake system is getting too expensive and dangerous. I want to convert it to the vacuum system. I see Gbodyparts and Kirban sells the kits. Kirban's is much more expensive. Is it better? Anyone else these sells these kits? Thanks.
I got the hydroboost system from Kirban years ago. It's one of the best thing I've done with the car. I totally trust it. I went through so many power masters before that. I was always waiting for the next time for the brake system to fail. That said..... I got it from Dennis Kirban. He even went to the shop I used and took photos as it was being installed; and posted them in his newsletter. I was a Kirban customer for about 30+ years. But now that the original Kirban's does not exist, I will look elsewhere when I need something.
Pic of the new hose to the booster!
Saw the window deal at the diesel drags yesterday....


  • 20230415_125041.jpg
    2 MB · Views: 109
  • 20230416_130745.jpg
    1.6 MB · Views: 117
I chose to route the hose behind the plug wires, under the coil/ module mounting plate to a tee right above the PCV valve. I like how it’s more hidden. It’s been working very well since ‘96.
Just another option.


  • FD1BE108-5C6C-462B-8024-C7B63B1842F3.jpeg
    518.5 KB · Views: 91
That works with a stock or small cam, but the PCV valve is a constant vacuum "leak" and will reduce the vacuum to the booster if it's "Teed" off of it. If it works, cool! If the vac is too low, you need a different way.
I have a .589 lift roller, so I did it this way.
Whatever works for all you folks! You have alternatives!
There is a billet booster check valve made by Earl’s thats next on my list.
They’re made in black and silver.

Cool if you like the look and want to spend $60.00. But, being anal, I talked with brake parts vendors and found that there is a federal standard for the plastic check valves and they have to hold up to repeated backfires, at a much higher pressure than we boost to. For the heck of it, I connected a regulator, a "T" with a gauge on it, and cranked up the pressure. It didn't fail with 50 lbs on it! I figured that since I won't be making that much boost, I'm probably golden. A pvc valve is metal and cheap, and old Mopars used nice machined pvc valves with a hose barb on each end on most of the 70s V-8s. They had a barb on the crankcase side because they were stuck in a grommet in the rocker cover.
As a guy with a reputation for over thinking everything, even I think you are over thinking this!
Besides, if that beautiful vac booster valve still has a rubber "petal" type valve, the housing may take hundreds of PSI, but the rubber diaphragm would still fail first anyway.
I think I have one laying around, and if I do, I'll post a pic. JMHO
Put this in line between the plastic one and the intake manifold. It will absorb the boost and take the load off of the plastic stock valve.


  • 20230417_103200.jpg
    1.1 MB · Views: 79
I used a "T" fitting off of the PCV & was able to hide the vacuum line. That seemed to work OK for general driving. When I began to add a few upgrades (new turbo, RJC PCV valve) & wanted to power brake the car to launch, it didn't work very well. The vacuum signal was weak. It might work well if you have a functional OEM GN PCV valve. I did not have one & they are NLA. Rig up a temporary vacuum gauge inline & see how much vacuum you have to work with.
Got to be careful with those fancy schmancy check valves as ''added insurance''. Check valves has a 'cracking pressure' rating on them if there's a spring involved. If the cranking pressure is greater then engine vacuum, the valve will stay capped off and the booster will never get a charge under light throttle driving.
If the engine RPMs never get high enough to cause high vaccum during a throttle shop, you could run out of reserve vacuum.
And those plastic charcoal filters are very scary now. They seem to be made of paper thin plastic now with a pretty weak glue joint.

I don't send them with my brake kits for that very reason. Plus, they only exist to absorb fuel vapors from float bowls. And since we don't have carbs, there's no fuel bowls to worry about.
I'd be leery of a vacuum conversion. If the last owner hadn't done it I would have gone hydroboost. My vac brakes wont lock up the tires on an emergency stop. Not even close. Almost hit a car because they pulled out in front of me. Both feet on the pedal and it hit the pedal stop. Yes all the valves are working, yes i've bleed the brakes, yes it has the proper vac pedal, and yes the rear drums are adjusted properly. Just not enough stopping power in my opinion. There's also a huge "dead spot" in the pedal. It moves like maybe 2 inches before actually doing anything. My old 87 with the PM didn't have that problem.