1stDeuce
Gold Member
Glyford, you for got the leading * before your statement... 
* = Modern
From the mid-80's back, trucks with hydraulic brakes used a hydrovac booster. It's run off vacuum, and is typically mounted behind or just under the cab, and the only thing on the firewall is a bare master cylinder. OP's Int'l is right at the changeover, so either system could be there, assuming it's not an air brake truck...
I'd much prefer hydroboost over hydrovac... My truck with hydrovac brakes does not stop quickly when fully loaded, and I've heard that pressure readings from most hydrovac units max out around 1000psi. Hydroboost will get you up above 1500psi. Quite a difference!!
* = Modern
From the mid-80's back, trucks with hydraulic brakes used a hydrovac booster. It's run off vacuum, and is typically mounted behind or just under the cab, and the only thing on the firewall is a bare master cylinder. OP's Int'l is right at the changeover, so either system could be there, assuming it's not an air brake truck...
I'd much prefer hydroboost over hydrovac... My truck with hydrovac brakes does not stop quickly when fully loaded, and I've heard that pressure readings from most hydrovac units max out around 1000psi. Hydroboost will get you up above 1500psi. Quite a difference!!