1950s 1955 vacuum hose routing

[alzink]

putting my rebuilt 1955 331 back into the car and have forgotten the vacuum hose routing.
no vacuum to radio as I replaced it with a modern version
no vacuum to brake as I don't see it as necessary

so I need routing of windshield wiper, washer, and vacuum advance (not sure I need that as I installed a petronix ) and anything else I might have missed

Thanks

[35-709]

You keep the vacuum advance with the Pertronix.

[Roger Zimmermann]

no vacuum to brake as I don't see it as necessary

No power brakes? I would not drive your car!

[Jeff Rosansky CLC #28373]

On ours, the line on the base of the carb goes to the vac manifold on the firewall for the radio and wipers. The one on the manifold just in front of the carb goes under the manifold to the vac advance.
If I remember correctly, the manifold on the firewall passes thru to feed the radio. So if you aren't using it for the antenna then be sure to cap it off.
Let me know if you need anything else.
Jeff R

[dn010]

No power brakes? I would not drive your car!

I drove my 57 for years with the vacuum to the booster disconnected, as the booster was inoperable and requiring rebuild. It is very appreciated when it is working again.

[tluke]

So Jeff may have remembered backwards. The small metal vacuum line coming off the bottom of the front of the carb bends toward the right and is routed under the manifold directly to the vacuum port on the distributor. The larger metal vacuum port line on the manifold in front of the carb curves around left and heads to the back of the engine. (Click pictures to see full size)

At that point the metal line connects with a rubber vacuum hose into driver side port on the two bottom ports on the vacuum manifold on the firewall.
The next picture shows the various rubber hoses on the vacuum manifold. As shown there are two ports connected to vacuum, the one just shown above connected to the manifold vacuum and one going down the rear of the engine and connecting to the oil pump vacuum assist port. A port at the back of the vacuum manifold goes through the firewall to the radio so that port needs to be capped if not connected to the radio. The other two ports on either side go one to the wiper motor and the other to the windshield washer jar. The third pic shows the pink hose that goes to the wiper switch inside the car and the blue host that goes to a connector on the washer coordinator off the driver side of the wiper motor.

The brake booster is connected via the large rubber hose also shown in the top picture coming off the very front of the manifold (shown bending to the right towards the booster).

[Michael Petti]

When my booster on my 60 needed rebuild it was like stepping on a brick. I considered car undrivable.

[5390john]

There was an article in the Self Starter in the last 2 or 3 years describing how to rebuild the firewall vacuum line distribution manifold with a new "check valve" component gasket.
I did this on my '55 and it made a HUGE difference in the performance of the vacuum system.
I WOULD STRONGLY recommend doing this rebuild, it's really easy and well worth the time!
John Adams   

[David King (kz78hy)]

I made the seal/valve that goes in the check valve.

https://keepemrunningautomotive.com/shop/ols/categories/group-38

[Roger Zimmermann]

There was an article in the Self Starter in the last 2 or 3 years describing how to rebuild the firewall vacuum line distribution manifold with a new "check valve" component gasket.

John, that description is also here: https://forums.cadillaclasalle.club/index.php?topic=108350.0

[Jeff Rosansky CLC #28373]

So Jeff may have remembered backwards.

Well, it is possible. That is how ours was plumbed when we got it. The line going to the distributor was hard metal the whole way and made it very hard to turn it so I spliced it and out a rubber vac line in the middle. Mine also goes under the manifold instead of above as in your picture. All seems to run well.....
However it is possible that mine has been wrong from the start I guess.

Jeff R

[tluke]

Now, before this thread I didn't even think about which vacuum line was connected where but I assumed since the vacuum advance didn't kick in until you give the engine some gas, it might have something to do with the throttle and carburetor. Being the curious person I am, after Jeff's last post I did a quick search to fill in a bit my lack of knowledge. Here's what I found:

Manifold vacuum comes from a source BELOW the throttle blades. Vacuum coming off the carburetor is "ported" vacuum and will not register vacuum until the throttle is opened. Ported vacuum is vacuum that is low at idle and increases as you give it gas. Engine vacuum, available ABOVE the throttle plates of a carburetor, is used to advance ignition timing when the throttle is opened above its idle position. A ported vacuum connection will not register vacuum until the throttle is opened. A manifold connection will register vacuum anytime the engine is running at closed (idle) or part throttle. At Wide Open Throttle (WOT), vacuum will be at or near ZERO.

So Jeff has his car running well with the vacuum advance off the intake manifold so I must conclude you can time the engine such that it works that way. However, since the rest of his accessories (wipers, windshield washer, antenna) are running off the ported vacuum on the carburetor, which doesn't provide vacuum at idle, I have to guess those accessories don't work when sitting at a stop light (or at wide open throttle climbing a hill).

Just FYI

[alzink]

Wow,

Thank you all !
If I have further questions, I'll get back to you
The newly rebuilt 331 and transmission are going back in in a few weeks then I'll figure out the routing

[alzink]

I have to correct my first comment re the brakes. The vacuum I eliminated was the vacuum asset to the emergency brake not to the vacuum to the booster. Thanks for the comments

[Jeff Rosansky CLC #28373]

I have to correct my first comment re the brakes. The vacuum I eliminated was the vacuum asset to the emergency brake not to the vacuum to the booster. Thanks for the comments

Not sure I understand....... There is no vac assist to the emergency brake.
Jeff R

[alzink]

Hmm... I'l have to check it out and get back to you

Thanks

[alzink]

you are correct about the
brake assist vacuum. I got it mixed up with my 63
At 76 its happening more every day
Again thanks for all the input

[tluke]

Just to clarify since it wasn't shown in my diagram in my post of 2/19/24, the vacuum goes from the vacuum manifold through the firewall to the rear of the radio as I described but then there are two hoses that go out from there under the dash and out to the antenna, one for up and one for down.