Rochester M Vacuum Attachment - The 1947 - Present Chevrolet & GMC Truck Message Board Network

notahybrid · 06-30-2008, 02:37 PM

I have a 68 c10 250 w/ a Rochester M monojet. Where is the vac advance hose supposed to attach? If facing the engine there is a tube on the right front corner at the base of the carb and on the left side of the carb there are 2 holes one on top of the other. I think this is where it was attached when I got the truck but the tube on the right has vacuum when you hold your finger on it.
Thanks

telly · 06-30-2008, 03:40 PM

I have a 70 C10 with a Monojet "M". My vacuum advance goes into the front right of the carb (where you are saying you feel suction). One of the spots on the left side on mine goes to the PCV.

I'm no expert, just bought my truck a little over a week ago - first one.

68gmsee · 06-30-2008, 05:07 PM

On my Rochester the vacuum advance goes to a port on the bottom left side of the carb as you're looking at it. The front one on the bottom right is also a vacuum port but is plugged with a rubber cap.

The PCV goes on a tube at the top of the carb that the breather attaches to.

The vacuum on the front is a constant vacuum.

notahybrid · 06-30-2008, 05:07 PM

Thanks Telly, I'll give it a try there.

notahybrid · 06-30-2008, 05:10 PM

68gmsee thanks for the post. There is a constant vacuum on the front right tube and I currently have it capped. I seem to remember that when I got the truck it was connected on the left side like yours. I guess I'll try both and see which works best.

68gmsee · 06-30-2008, 05:25 PM

I've tried it both ways in the past. For some reason that I don't recall, I put it back in the original position.

The manual says that the one on the left is the "Distributor Vacuum Tube." The one on the front bottom is for "Thermac Tube." I believe that's for trucks from California and other states that required emission controls.

notahybrid · 06-30-2008, 05:33 PM

Left it is... thanks again.

06-30-2008, 02:37 PM	#1
notahybrid Registered User Join Date: Mar 2007 Location: Chesapeake, Virginia Posts: 39	Rochester M Vacuum Attachment I have a 68 c10 250 w/ a Rochester M monojet. Where is the vac advance hose supposed to attach? If facing the engine there is a tube on the right front corner at the base of the carb and on the left side of the carb there are 2 holes one on top of the other. I think this is where it was attached when I got the truck but the tube on the right has vacuum when you hold your finger on it. Thanks

06-30-2008, 03:40 PM	#2
telly Registered User Join Date: Jun 2008 Location: Stanwood, WA, 98292 Posts: 151	Re: Rochester M Vacuum Attachment I have a 70 C10 with a Monojet "M". My vacuum advance goes into the front right of the carb (where you are saying you feel suction). One of the spots on the left side on mine goes to the PCV. I'm no expert, just bought my truck a little over a week ago - first one.

06-30-2008, 05:07 PM	#3
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Rochester M Vacuum Attachment On my Rochester the vacuum advance goes to a port on the bottom left side of the carb as you're looking at it. The front one on the bottom right is also a vacuum port but is plugged with a rubber cap. The PCV goes on a tube at the top of the carb that the breather attaches to. The vacuum on the front is a constant vacuum.

06-30-2008, 05:07 PM	#4
notahybrid Registered User Join Date: Mar 2007 Location: Chesapeake, Virginia Posts: 39	Re: Rochester M Vacuum Attachment Thanks Telly, I'll give it a try there.

06-30-2008, 05:10 PM	#5
notahybrid Registered User Join Date: Mar 2007 Location: Chesapeake, Virginia Posts: 39	Re: Rochester M Vacuum Attachment 68gmsee thanks for the post. There is a constant vacuum on the front right tube and I currently have it capped. I seem to remember that when I got the truck it was connected on the left side like yours. I guess I'll try both and see which works best.

06-30-2008, 05:25 PM	#6
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Re: Rochester M Vacuum Attachment I've tried it both ways in the past. For some reason that I don't recall, I put it back in the original position. The manual says that the one on the left is the "Distributor Vacuum Tube." The one on the front bottom is for "Thermac Tube." I believe that's for trucks from California and other states that required emission controls.

06-30-2008, 05:33 PM	#7
notahybrid Registered User Join Date: Mar 2007 Location: Chesapeake, Virginia Posts: 39	Re: Rochester M Vacuum Attachment Left it is... thanks again.



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