The Stovebolt Site Forums The Shop Area Engine Shop Brake Booster Vacuum Source on a 235???

Has anybody put a disc Brake Conversion on a '62 running a 235? I bought the kit (nice) because I plan on putting a 283 in this summer, but would like to maybe upgrade the brakes now so I can continue to drive it. The question is, where do you plug into the 235 for a Vacuum Source? has HUGE BOOSTER!!!

Some 235's have a 1/2" pipe thread in the intake just below the carburetor flange, bushed down to a 1/4" vacuum line for wipers. It's simple to install a bigger fitting to supply the vacuum if you have that setup. If the manifold is not drilled and tapped for the big pipe fitting, either enlarge the hole and rethread, of find another intake with the big hole already there. I'd reccomend removing the manifold before the drill/tap operation to keep metal shavings out of the intake!
Jerry

Thanks, I'll take a look. I don't have Vacuum Wipers though, so who knows.

I'm using the wiper vacuum hole on my 248. (I have electric wipers.) I love the power brakes.

A warning: in theory, the line to/from the booster is a dead end (no leaks) and should be able to run without regard to size. A large booster means (probably) a large volume inside the diaphragm, so that several stops can be made without "refreshing" the diaphragm from the manifold. When vacuum is exhausted, the pedal is hard until vacuum rises again.
The problem: if you run a large hose from the manifold, once the booster is at high vacuum the engine will not know it's there and the car will stop normally.
However, after a few stops in traffic, the diaphragm will try to re-charge from the manifold, and if you're idling the engine will see this as a huge vacuum leak - and stall.
I don't know the "correct" hose size (actually, the minimum fitting ID in the line), but I'd duplicate the original size if you can find it.
If not, I'd run a big line, but leave some fitting where you can reach it and insert a smaller fitting or restrictor if it stalls.
Why not just use a small line?
Because it takes a long time to fully re-charge a big diaphragm, and the engine will stagger for longer in seconds.
Best (although complex and annoying): use a solenoid valve in the line (hot with the key), which closes when the throttle linkage is fully relaxed - when you let off the gas, the valve closes. This will prevent any vacuum demand by the booster from reaching the manifold unless you're actually driving (when it won't matter).

If there's room for it, like on a 1-ton or bigger truck, try mounting a retired 30-lb. Freon canister somewhere under the frame as a vacuum reservoir. Use a 1-way check valve in the vacuum line from the engine to the tank. I just drill a correct-size hole in one end of the tank and install the stock rubber grommet and check valve from the booster I'm using, creating a double check valve setup- - - -one from engine to reserve tank, and the original one at the booster. If you're using a vacuum-shifted 2-speed rear end or vacuum wipers, the reserve tank smooths out the operation of those systems, also.
Jerry

...Or you can just put a little extra vaccuum in a coffee can, and pour it into the brake system when you need it!

True - a really big vacuum tank allows a very small line to the manifold, so the engine won't get nervous when the booster asks for more vacuum. Only downside: takes longer to fully drawn down to holding.