The Stovebolt Site Forums The Parking Lot Big Bolts booster vacuum line routing

Hello again with a few questions re: the modified boosted brakes which I'm installing on my 58 Spartan 80 (I'm using a 'modern' 1970s-80s booster, originally from a medium duty International). I'm having a brain fart: 1) Is there any functional difference between placing my reserve vacuum tank in-line from manifold to booster, as opposed to tee-ing it from a T fitting at the booster vacuum connection (it makes a lot more sense for me to run the main line down the left frame rail, to the booster, then just as it is about to enter the booster, add a T fitting, allowing a line to the reserve tank to cross to the right frame rail where there is room to mount the reserve tank).. 2) in using a reserve tank, is there a necessity of using a second check valve, aside from the one on the firewall above the manifold? 3) would the original 1.5 inch master cyl be sufficient to operate this 'modern' booster? Your ideas and experiences very much appreciated!!

That sounds right...out of the manifold to the check valve high on the firewall, then down to a T on the drivers side at the Hydrovac, then out of the T and over to the tank on the passenger side. I think 1/2" copper will do the trick!

There could also be a fresh air intake on the Hydrovac that should have an air filter on it or be piped back up to the engine air cleaner to keep dust/dirt out of the Hydrovac piston chamber. Some trucks had what looks like a valve cover breather attached to the inside of the cab either behind the dash on the firewall or behind the seat on the floor.

Your existing MC will work fine...

Mike B

What Mike said ^, with just one check valve, not two.

Mike and Mac, many thanks! I am using copper tubing (I'll double check the size, but it's not small).....also I did see the breather on the inside of the firewall, but not sure what size line I should use to connect to it.....and good to know that the original MC will work and that a single check valve is all that's necessary. Thanks again!

The size of the tubing is important, it needs to flow properly so that the booster reacts quickly to the pedal movements. Just do not downsize it and keep it as short as practical.

Got it....thanks for the added info!

The fresh air tubing/hose should be the same size as the nipple on your Hydrovac...it could be 1/2" or 3/4".

My Illustrated Parts Book shows the 1962 trucks used 1/2" steel tubing (if needed I'll dig to confirm '58 is the same), but I think copper will be just fine.

Mike B

Good, thanks for the added info!