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Power Brakes Using a Buick Grand National Master Cylinder

by: Joe Leone

Here's the list of fittings needed for the Buick power brake setup. All these numbers are from Amstreetrods.com.

1-592048S -03AN to 9/16-18 IF (large MC port)
1-592046S -03AN to 1/2-20 IF (small MC port)
1-972054B -03AN branch to 3/8-24 IF run tee (for front brake lines)
1-961603 -03AN to 1/8 IPS (this connects rear m/c hose to rear line assuming use of prop valve)
1-12" -03AN straight to -03AN 90 hose for rear
1-16" -03AN straight to -03AN 90 hose for front

The above connects your Buick MC to the tee and prop valve. With Tristate lines, the fronts will have to be reflared, since the left front is a metric and the right front is SAE. Better to reflare than use multiple adapters. For my case, they were a bit too long anyway. If length is okay, then you'll need 1 10mm-1.0 IF female to 3/8-24 IF male adapter to connect the left front line to the tee

To relocate the pump unit, use the fittings below

1-592042 -04AN to 10mm-1.0 male
1-989544 -04AN to 10mm-1.0 female

Appropriate length of -04 hose with straight and 90 ends. Unscrew the rubber hose from the hard line and insert the extension hose with the above adapters.

Appropriate length of Earl's Auto-flex hose, -06 size for return line to pump. Use any suitable clamp, like Earl's Econo-fit

My list is accurate for my application: The electric power unit was relocated to the front "X" member, and the "T" and prop valve were mounted on the lower 3/4" tube, 16" in front of the driver footbox. If you don't relocate the power unit, you'll need much less stuff. The whole list was about $140 from amstreetrods.com. The numbers, for the most part, are generic. You should be able to shop around without too much trouble.

If you are installing the Buick GN setup, and are relocating the electric pump unit, as I did, be sure to save and use the rubber hose from the pump to the master cylinder. Braided hose is okay to extend it, but not to replace it completely. The reason is that the braiding on the AN hose will ground the motor and it will never shut off. I used AN hose and inserted the old line at the master cylinder end, so it would not show, and I covered the AN with clear plastic so it would not ground on the way to the pump unit. The return line isn't so much a problem because it connects to the non-conductive reservoir at one end. It should still be insulated, though, if it's braided.

All I can tell you is that the Buick setup requires the least amount of frame modification. All I did was enlarge the holes in the firewall to account for the slightly wider bolt spacing, and I had to rig a pivot for the pedal. I'm a total amateur at metal work of any kind and I had no trouble once I thought it through. I'll post some pics if you want.

I ground off the weld on the back of the pivot pin on the pedal arm and drove the pin right out. I then cleaned up the welds and found an appropriate bushing at the hardware store to reduce the hole in the pedal to that of the pushrod. Then I used a short grade 8 bolt with a nylock castle nut and used a cotter pin as an extra safety.

Autozone Part Number 52-9700

 

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