View Full Version : Vacuum Routing
08-16-2014, 12:53 AM
There is one hose coming from the front of the carb just to the left on my Holley 80457-3. I have looked everywhere trying to find a diagram or explanation where that line would go. I looked at our shop manual, electrical manual and on Holley sites. Because the original should be the Autolite 4100 I have not been able to locate any info or pictures where this hose should attach too. Would anyone know what resource or site I can use? Maybe I missed a page in the manuals I have? The picture below shows the hose to the left with a screw temporarily placed in it.
08-16-2014, 11:42 AM
Replacement carburetors have many more vacuum connections then the original Autolite 4100 because they are used on a variety of different model cars. Since it's not being used it's plugged. Just keep it plugged and you'll be fine.
08-16-2014, 01:37 PM
Thank you. When I was dealing with a fuel fitting leak, the hose was not attached to anywhere. I looked all around and could not find where it was connected. With the engine running at idle, it has suction. I plugged it with a screw until I could find its source.
08-21-2014, 07:34 PM
I ended calling Holley and got an answer to my carb question. They told me the hose that was not connected in my picture and where I temporarily inserted a screw should go to the automatic transmission. That hose has either become unhooked from the transmission if it in fact it goes there or has been sitting not connected to anything for who knows how long. I have been looking in the manual for a diagram of where that connection point may be. Has anyone had to deal with that on our cruise-o-matic and does anyone where it would connect to?
08-21-2014, 08:18 PM
Normally the vacuum modulator on the COM is fed from the power brake check valve, not the carburetor. If you want your engine to look original you will have to get an Autolite 4100 carburetor to replace the Holley. If you are going to stick with the Holley then you will have to live with the vacuum ports being plugged. It's your choice.
08-21-2014, 10:14 PM
Ok thank you John, I guess I'm really trying to figure out if that port that was not hooked up and had no cap or screw on it, was actually hooked up and recently fell off or has not been connected anywhere and just sucking air for who knows how long. When I discovered it and found out it is just drawing air I looked around and could not see any other end or loose hose so I plugged it with a screw. Thats why I asked the question. This may explain the difficulty I had in doing the timing recently. The car is pretty close to original and I will get closer as time goes by but for now I am trying to get her mechanically sound and safe and worry about originality as parts need replacing. When I see a hose thats unhooked and open like it was I tend to get a bit "panicky" being the novice that I am. I assume then from what you wrote that the Cruise-O-Matic has a vacuum port going to it from the power brake check valve. I will look at that and keep the vacuum port capped. Thanks for your information.
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