View Full Version : Vacum boost for power brakes on a 390
05-25-2011, 02:03 AM
Does anyone know where I can find the correct route for the vacum hoses for the Power brakes on a 390? Engine is from 64, so I canīt follow my Shop manual as the 352 looks quite different. My brakes are so bad there must be something very wrong. And please, I will not convert to disc brakes. Yet... ;)
05-25-2011, 02:05 PM
Should be the same as a 352cid in a '58 T-Bird.
05-25-2011, 03:13 PM
Need to check again then....:o
05-25-2011, 05:06 PM
Searched the web for pics of a '64 with the hood up and enough detail to see the vac lines - no real luck other than this.
I guess the best bet would be to post this question on the Flairbirds forum and see if you can get one of the fellows there to send you a pic of their vacuum setup.
The '64 390 would have PCV or EGR but maybe it has the same vacuum tube as the 58-60 for the brake booster??? Is the vacuum reservoir under the drivers side fender leaking? - should only matter after the engine is stopped or in low vac conditions but if it had a BIG hole that probably would not help.
Hope you find the info and get those brakes stopping.....
05-25-2011, 05:19 PM
I took out the vacuum tank inside the left front fender and it was pretty much like new :) Changed the hoses while I was at it.
But as I one of two vacuum hoses from the engine is ( by purpose-donīt know why though.. ) is cut & blocked, - the one that still is on here, I thought I need to understand where this was suppose to go in the first place... Se pic.
05-25-2011, 06:29 PM
That is the vacuum booster on top of the fuel pump for the wipers. On my fuel pump in the cricular area between the hoses it has "wipers" and a small arrow pointing to the tube futherest from the coil (the one that is connected in your pic). That hose goes to a steel line that runs back up and across the motor in front of the carb to the passenger side of the car where it connects to another hose to enter the passenger compartment and then to the wiper motor (it is just hanging on the back of my picture because I have it disconnected at the moment - it might appear that it is connected to the manifold but is not).
The hose in your pic that is disconnected goes to a steel line that goes up and to the vacuum junction block just behind the distributor.
Hopefully this picture will help although you cannot see the fuel pump you can see the steel lines I am speaking of. If you need a different or better picture just say the word and I'll get it posted.
05-26-2011, 07:28 AM
Aha! That might explain why I have such a poor performance on my vipers? They only works when I go off the throttle....
Alan H. Tast, AIA
05-26-2011, 02:31 PM
Regardless of year, the primary vacuum source comes off of the engine, typically from the intake manifold. On Squarebirds with original manifolds the vacuum pull-off point is found between the carburetor and distributor, with a steel line/tube and related brass fitting threaded into a hole in the manifold. This is the "junction block" mentioned in the previous response. The photo of the '60 that's part of this thread shows the tube that runs past the driver's/left side of the carburetor and turns outboard with a short length of hose attached for connection to the rest of the '60's vacuum-dependent components downstream such as the vacuum reservoir, power brake booster, wiper motor, etc. I won't get into specifics of how a specific model should be plumbed as it depends on what accessories are installed and if it has the dual-action fuel pump like what's shown in Anders' photo. This vacuum pull-off point was used through the '61 model year, after which the port was either blocked off with a pipe plug or the opening not machined into the casting.
Starting with the '62 model year, and in this case for the '64 390, a brass fitting for the vacuum line was screwed into the intake manifold to the rear of the carburetor and to the passenger/right side. As steel tubes/fittings were not used for '64, a brass junction block set up for vacuum hoses was used: off of this fitting a large vacuum hose ran directly to the power brake booster, and a small hose supplied vacuum for the heating/air conditioning system.
Assuming you are using a C4AE- or C4SE-numbered intake, the vacuum line routing would have to be improvised by either using vacuum hose from the '62-newer fitting and running it to the connection for the brake booster, vacuum reservoir and wiper motor, or finding a brass fitting that would accept a tube nut and OEM-sized steel tubing (3/8" OD? I don't remember the size off the top of my head) across the top of the manifold over to where the connection hose is shown in the aforementioned '60 engine bay photo. Or, you could dig up an original, correct-for-year intake manifold and run lines per original. Routing for vacuum lines and hoses are shown in rerproductions '58, '59 and '60 T-bird Electrical Assembly Manuals.
05-26-2011, 04:45 PM
Thanks for the explination Alain.
I follow you all the way until the last part, and yes, I have that junction box as you describe, where it starts to get complicated with 62 model and OEMīs....:o
Need to translate more accurate and check my engine and follow all treads to finally get it.
I have a C4SE intake. I also have a a brass plug on the passanger side just on the side / behind the carb. Shall I find / make something to that hole and connect it to the "Wiper" vacuum hose? Will that give me better wiper function, I do it right away :)
Alan H. Tast, AIA
05-26-2011, 05:00 PM
First off, where are you getting vacuum from? If the hole behind/rear of carb is plugged, then you're getting it from somewhere else. Is the vacuum coming from a spacer between the carburetor and intake? The '64 manifold was set up for a PCV system that had a hose barb on the back of the manifold, a set of hoses and tubes connected to a fitting that the PCV valve screwed into, and in essence pulled crankcase fumes from the rear of the manifold through the PCV filter into the spacer under the carburetor. Is the hose barb at the rear of the manifold removed or blocked off/plugged?
Pictures help, too. Show us what you got.
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