I am having a problem with the idle on my 1960 olds 88. It has a 371 with rochester 2G carb. It acts as if it has a vacuum leak but I cannot find a leak anywhere. I disconnected all vaccuum hoses one at a time and capped the ports off with no change. I sprayed carb cleaner all around to find the leak and could not find it. With vacuum gage hooked to the manifold port, the car will hold 20 but then will come down as low as 10 over time. It is real irratic. The car idles great at 20 but barely idles at 10 of course. When I put my hand over the carb partially, the idle revs up and sounds good. When I completely cover the carb the car dies as it should. The car runs slightly rich based on the smell but doesnt smoke. It runs great, just has a problem with the idle. Pushing the power brake pedal makes the idle worse and the car dies. Also, the brakes are very hard to push and it feels the same with or without the booster vacuum line hooked up.

What I really dont understand is that with all vacuum lines disconnected and ports blocked on the carb it has the same symptoms. Could the carb have an internal vacuum problem and be ready for a rebuild? I am at the end of my knowledge of troubleshooting vacuum leaks.

Other things to note: there have been no changes made to timing or vavle adjustments. Car ran great when I first got it.

Any help is appreciated

 

You've found your problem. It's the power brake booster.

Try plugging the port to the vacuum booster and see what the car does. Just remember you'll have no power brake assist. Booster can probably be rebuilt easily enough; they were firewall-mounted by then and very similar to later cars.

Edit- just saw where you say it acts the same regardless of vacuum lines plugged. It's possible the carb power piston is causing it, as when vacuum drops it should move in its bore and allow more fuel- which could also explain your rich smell.

Won't hurt a thing to rebuild the carb.

And if you're stuck using E10 fuel, that ain't helping things. The people who mandated use of that stuff should be forced to drink it.