The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Newbie thinking about diving into a '65 GMC 1000

Praxiss454 · 07-28-2016, 02:01 AM

So I was trying to adjust the Rochester model b carb this evening prior to setting the timing, but my service manual stumped me. It's instructions were to:

1. Disconnect spark advance at distributor
and plug opening of tube.
2. Connect tachometer at coil.
3. Connect vacuum gauge to manifold.
4. With engine running (choke wide open) adjust
idle speed screw to bring idle speed to 450-500
rpm (Pow-R-Flo in drive, manual transmission in
neutral).
5. Adjust idle mixture screw to obtain highest
steady vacuum at idle speed.

I couldn't figure out where to connect a vacuum gauge. I assume this is NOT talking about the vacuum advance line from the carb to the distributor, because at idle that should not be pulling a vacuum.

Can anyone point me to exactly where I hook up the vacuum gauge?

07-28-2016, 02:01 AM	#125
Praxiss454 Registered User Join Date: Jun 2016 Location: Novato, CA Posts: 519	Re: Newbie thinking about diving into a '65 GMC 1000 So I was trying to adjust the Rochester model b carb this evening prior to setting the timing, but my service manual stumped me. It's instructions were to: 1. Disconnect spark advance at distributor and plug opening of tube. 2. Connect tachometer at coil. 3. Connect vacuum gauge to manifold. 4. With engine running (choke wide open) adjust idle speed screw to bring idle speed to 450-500 rpm (Pow-R-Flo in drive, manual transmission in neutral). 5. Adjust idle mixture screw to obtain highest steady vacuum at idle speed. I couldn't figure out where to connect a vacuum gauge. I assume this is NOT talking about the vacuum advance line from the carb to the distributor, because at idle that should not be pulling a vacuum. Can anyone point me to exactly where I hook up the vacuum gauge?