VCCA Home Forums TECHNICAL - 1945 AND NEWER 1946-1948 7" power brake booster and dual master.

Has anyone installed the above combo under the floor? How well did it work, did you encounter any problems installing the unit? My 47 has a 235 and I was told it did not produce enough vacuum for this application. Any input would be appreciated.

A 235 with a stock camshaft should produce more than enough vacuum. The 1958-1962 235 used an even larger vacuum booster and with no problem.

Thanks, its a 58.

In order to produce 18---23 inches of vacuum to work a dual diaphragm 8" booster, or single diaphragm, your most likely going to need a SSBC vacuum pump.

I had the same problem and that's how I sorted it out. Its mounted to inside of the frame or you can put it in the trunk.

To see if you have enough vacuum to operate the unit, use a vacuum gauge.

8" DUAL DIAPHRAM produces more pressure than single booster. Under the floor your going to need residual check valves to stop brake fluid draining back to master. Disc and drum use diff size poundage check valves. Also the brake lines for disc brakes are 3/16, drum is 1/4"

Use corvette ** dual master cylinder** with 1" bore or 15/16" from earlier. Also use the GM correct combination distribution valve. They are available for DISC-DISC , DISC- DRUM, DRUM- DRUM.

Get it right and you will be a happy owner.

mike lynch