What's the most common sources for vacuum leaks on a 73 400?

[WH23G3G]

I got my 400, timed at 7.5 degrees BTC and idling in park at 750-800RPM. Takes a lot to get it fired up after it sits a few days or even a day. It doesn't like the choke or it's a vacuum leak. Once it's warmed up a couple minutes you can drive it. I've only driven around my block because it feels like the transmission is surging but not shift hard, just surging before it shifts. So I've only gone about 45MPH. Other than that it will run and drive but when you back it up into the driveway you have to have your foot on the gas for sure or it will stall out. Same thing right after it starts and you try to put it in drive. I recently had the Thermoquad restored by a company and before I mess with the mixture I called their tech line. I told them what was wrong and they said it sounds like a vacuum leak. I asked an older mechanic familiar with the cars back in the day and he said the same thing, a vacuum leak. I know I've heard about big block manifolds have vacuum leaks. I have the OSAC valve, ported vacuum swithc, and the air cleaner temp sensor all hooked up on my 73, but all the hoses are new, not brittle. I can try and take all the vacuum hoses off and plug everything, but would I want to plug up the ported vacuum switch and vacuum advance? Then they said if that doesn't work the manifold might be leaking. Where do they usually leak at? I just used the valley pan when I rebuilt the engine, no fiber gaskets, I did use RTV supplied with the pan. Is there a safe way to test for intake vacuum leak? I don't want to spray brake clean all over and accidentally hit the alternator. If it's a manifold I was going to change to the Edelbrock 2186. Is that a good choice? I know one of the bolt holes the carb bolts into had a corner broke off, but the bolt still goes in right and tightens up.

[flyinlow]

Most vacuum leaks are old vacuum lines or carb bases  not sealling to the intake.

One way to find vacuum leaks is with a can of carb cleaner. With the engine idling, warmed up,choke off, remove the air cleaner and plug the vacuum line to the air cleaner snorkels. Using the tube that came with the carb cleaner, spray around the base of the carb , the intake to head mating surface, and the EGR valve if installed. If you spray near the leak the engine will speed up (and usually smooth out). Don't let the cleaner go in the top of the carbs airhorn or it will speed up and make locating the leak harder. If you can reach it spray under the intake to check sealing on the underside of the intake. Check the ten thru bolts on the TQ are snug. Don,tuse a Quadrajet carb base gasket on a Thermoquad ,instant vacuum leak. They look similar.

Power brake hoses,check valve and sometimes the booster can cause vacuum leaks. An EGR not closing completely can cause rough idle,and vacuum leaks.

These are a few of the more common leaks.

[Mopar Nut]

Most vacuum leaks are old vacuum lines or carb bases  not sealling to the intake.

One way to find vacuum leaks is with a can of carb cleaner. With the engine idling, warmed up,choke off, remove the air cleaner and plug the vacuum line to the air cleaner snorkels. Using the tube that came with the carb cleaner, spray around the base of the carb , the intake to head mating surface, and the EGR valve if installed. If you spray near the leak the engine will speed up (and usually smooth out). Don't let the cleaner go in the top of the carbs airhorn or it will speed up and make locating the leak harder. If you can reach it spray under the intake to check sealing on the underside of the intake. Check the ten thru bolts on the TQ are snug. Don,tuse a Quadrajet carb base gasket on a Thermoquad ,instant vacuum leak. They look similar.

Power brake hoses,check valve and sometimes the booster can cause vacuum leaks. An EGR not closing completely can cause rough idle,and vacuum leaks.

These are a few of the more common leaks.

What he said.