Monthly ArchiveMarch 2015

Buick Brakes, Part 2

Back in Part 1, I described some of the issues with braking on my 1987 Grand National. In this installment, I’m going to explain what I went through to convert my car to a manual brake setup.

The first thing I did was call Wilwood, who manufactured the front brake kit I already had on my vehicle. My kit is a now-obsoleted 10.75″ disc brake kit with Dynalite four piston calipers. While the rotor diameter is only slightly larger than stock, the rotor is much thicker and mated to an aluminum hub. The setup fits behind the stock 15″ wheels.

Wilwood took the information on the brake system, and recommended a 15/16″ master cylinder. The master cylinder size is based on the total piston diameter of the axle with the largest pistons. The weight of the vehicle has no bearing on master cylinder selection. I see that taken into consideration in internet discussions about master cylinders, so I’m putting it out there: it doesn’t matter. You need to know the piston area.

Wilwood 261 series master cylinder kit, I got mine in black

Knowing the proper master cylinder size, I hit Summit Racing and ordered a Wilwood master cylinder kit. It included a master cylinder and an adjustable proportioning valve. I also grabbed a 10psi residual pressure valve to go into the rear line.


Old and busted. Master cylinder, booster, and vacuum reservoir

Once I got it in hand, removed the existing components. This pile weighed 16.4 pounds. The replacement parts weigh just four pounds.

Now for the kicker: the Wilwood master, and just about any other will not bolt to the firewall. You need an adapter bracket. In my case, I was fortunate enough to still have my old PowerMaster. The PowerMaster used a 7:1 pedal ratio, so the bracket for it aimed the rod at the pedal at the proper angle for a manual pedal (6:1). I removed the bracket, cleaned it up, painted it, and sat it on the heater to cure the paint a bit faster.

PowerMaster brake bracket

Once the paint was dry, I bench bled the master and bolted it into the car.

New Master Cylinder!

Now came the hard part. Lines. This was a mess. The factory lines don’t have the proper ends to screw into the proportioning valve. They also connect to a combination proportioning/residual pressure valve/distribution block on the driver side frame rail. This block also serves as a mounting point for a bracket that’s involved in the transmission shifter linkage. This valve has to come out, or it will negate the fancy proportioning valve I just bought.

Factory proportioning valve is hidden behind that plate

Making things worse, the line coming out of this valve going to the rear brakes was a 1/4″ line, which all the other lines are 3/16″. The fitting on the rear line is also goofy metric fitting that you can’t get a union for. I had to cut the flare off the rear line, remove the line nut, and splice in a pre-flared section using a compression fitting.

Also, if you are running drum brakes in the rear, you must install a 10psi residual pressure valve inline between the rear drums and the proportioning valve. This residual pressure valve will keep the rear wheel cylinders pressurized at 10psi all the time. This will act against the return spring in the drum assembly and keep the shoes pressed against the drum. Without it, the shoes will pull off the drum, and you’ll waste your first pedal press pushing the shoes back against the drums, possibly crashing into somebody in the process.

Once other thing I learned: Harbor Freight’s tube flaring kit sucks. Don’t use it. Just get the pre-flared lines from the parts store and bend them to length. If you have to cut one, use a compression union to put it back together.

For the front brakes, you need two 3/16″ lines with 3/8″-24 tube nuts. I got two 30″ length sections, and two unions. Carefully bent

Unions joining lines coming from the new prop valve to the factory lines going to the calipers

up, they easily screwed into the bottom of the proportioning valve, and the unions allowed them to easily mate with the factory lines going to the front calipers.

Detail showing connections to the rear line: the compression union, 3/8″ inverted flare union, then the 3/8″ to 3/16″ adapter, then the 3/8″ nut on the 3/16″ tube going up to the residual valve.

After the lines were all hooked up, I used 1.5″ steel tubular spacers to¬†replace the transmission linkage bracket that had been bolted to the old proportioning valve.

The next step was connecting to the pedal. The Wilwood master has a rod coming out of it that’s threaded for a 3/8″-24 rod end to use as a clevis. The brake pedal I swapped in when I converted to vacuum brakes also had a hole in it already in the exact spot needed. Sadly, I couldn’t find a rod end that would work, so I made my own Clevis out of a piece of bar stock and a steel tube. It’s ugly, but it works. Alternatively, it might be possible to remove the pushrod in the master and replace it with the pushrod from the master or booster you already have. I didn’t want to take apart my shiny new parts.

After all that, the brakes still sucked. I suspected air was trapped in the system somewhere and it needed to be power-bled, so I dropped the car off with my good friends at Grossman Tuning. Not only did they power bleed it, they re-adjusted the rear drums and dialed in the prop valve for me.That’s all! The brakes take a lot of effort, but they work great, and they work the same way every time, boost or not.

Parts List:

  • Wilwood 15/16″ master cylinder and prop valve kit, PN 261-13626-BK
  • 10psi Residual pressure valve, 260-1876
  • 2x 30″ long 3/16″ pre-flared brake line
  • 2x 3/8″ inverted flare unions
  • 1x 12″ long 1/4″ pre-flared brake line
  • 1x 1/4″ tube compression union
  • 1x 78/” inverted flare union
  • 1x 3/8″ to 3/16″ inverted flare adapter (to adapt rear brake lines to 3/16″ lines coming from master)
  • Brake Fluid
  • Hardware for making a clevis to mate the pedal to the master cylinder pushrod



Buick Brakes, Part 1

A longstanding issue with my car has been sub-par braking performance. The GM G-Body suffers from woefully substandard brakes, especially when compared to modern cars. Tiny 10.75″ vented rotors up front with single piston calipers and 10″ drums out back on a 3600 pound car do not inspire confidence.

Piling on with the Grand National came the prospect of positive manifold pressure getting past the vacuum check valve on the vacuum booster. This would pressurize the boost and result in no power assist after a full throttle blast.

GM attempted two solutions to this problem. In the 1984-1985 non-intercooled cars, the used the HydroBoost system, which gets pressure for the booster from the power steering pump. In

1986-1987, they switched to the PowerMaster, a hydraulic system driven by a large electric pump.

The PowerMaster worked great off the showroom floor,

The PowerMaster Electro-hydraulic brake system

The PowerMaster Electro-hydraulic brake system

but time was not friendly to it. The unit was immediately involved in a recall where a pressure switch on top of the unit had to be replaced. The original would fail, the pump would run continuously, overpressure the rest of the system, which would leak, and you’d have no brakes.

As time wore on, the internal seals in the PowerMaster all eventually fall victim to the enormous pressures the unit operated under (3,000 PSI or more) and the caustic nature of DOT 3 brake fluid.

Many years ago, my PowerMaster suffered an internal leak, and I pulled it off. Replacing the unit wasn’t practical, as a reman unit was more than $500, and failure rates of the remans were high. So at the time, I converted to vacuum.

The conversion worked around town, but it did indeed suffer from pressurization of the booster when the turbo spooled up, resulting in many almost-didn’t-stop-in-time situations.

My attempts to fix this were mainly stopgaps. I added a vacuum reservoir and finally an industrial strength check valve. The stopped the pressurization of the booster, but the brakes still sucked.

I had two options: switch to a HydroBoost or go non-boosted. After watching my father wrestle with getting a HydroBoost working on his 1968 Cougar (it has a rather large camshaft and doesn’t generate enough vacuum to run a vacuum booster), I decided that simple was better and opted for full manual.



What happens when you run 26psi of boost on a stock Buick V6?

ThisBlown headgasket 1:

That little bit of currugated metal is the head gasket. It blew right at the top of cylinder #4. I was going 111mph in 3rd gear at the time at Lucas Oil Raceway in Indianapolis. It was the first time covering the quarter mile since I had converted the car to run on E85. It had never gone that fast before (previous best MPH was 104), so I neglected to shift into fourth, and the gasket failed somewhere north of 5000rpm.

Here’s another shot with the head off.
Blown head gasket 2

There was no other damage to the engine at all, but after measuring the cylinders, #4 was way out of spec, which prompted a rebuild.

Preparation of a 1987 Buick Grand National for SCCA CAM-C


Photo by Micheal Clevenger

Following the unfortunate, but necessary, sale of my Datsun, I was left with no car to race in my chosen sport: SCCA Autocross. I mean, I had this nice Cadillac CTS-V, which is a sporty ride, but I needed that vehicle to get me to work each day. It’s not a toy.

I spent half a season co-driving another friends’ car, and that was fun, but I like running my own stuff.

And then there’s the Buick. I have this 1987 Grand National. It’s in pretty good shape, and I’ve even occasionally autocrossed it just for giggles. It’s never been very good at it, but it looks cool doing it, and I get lots of compliments. Sadly, the SCCA’s classing structure didn’t cater to the car very well. Common modifications for Buick run afoul of several class rules, bumping the car all the way into Street Modified, a class for wickedly engineered, weight reduced, super-high power monsters on full race slicks.

Then came 2014. The SCCA announced a new class, Classic American Muscle. The stated aim was to try and get a piece of the burgeoning Pro-Touring movement, and steer these guys, who are spending gobs of money creating worthy vehicles from classic Detroit iron, into the SCCA. The class is pretty simple: The car must be from one of the big three, it must be rear wheel drive, it must weigh 3000 pounds, it must have a functional interior and be street legal, and it must be on tires with a treadwear rating of 200 or better. This class was made for the Grand National.

So, after blowing a head gasket and figuring, “well, I have to go through the engine anyway, lets see if we can make this pig handle, too.”

Following will be a series of posts documenting the engine rebuild, the suspension changes, and hopefully a successful 2015 season in CAM-C in the Kentucky Region SCCA. Stay tuned.