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Hi AJ:Yes, that area you have circled and sprayed into is where the THERMAC vacuum source would normally connect to. As the photo Blazer74 sent, there should be a 2" long metal pipe pressed into the carb body where a vacuum line would slip over. Your photo indicates that little metal pipe is not there...? If it was there it would be a simple measure of slipping a rubber vacuum cap over it. If it is just a hole in the carb, you either need to get that little steel pipe to press into the hole first or find a rubber stopper to press into it. It needs to be connected or plugged one way or the other to get your carb to work right. The THERMAC system was part of the oem air cleaner assembly to help the engine warm up faster when it is cold. That vacuum port in question operated a door in the air cleaner snorkel to allow varying amounts of hot air from the pass side exh manifold to be pulled into the carb. If you dont have this oem air cleaner anymore it is no big deal but after you plug that port you are probably going to need to retune your carb to see if problem was solved. Do you have any other unplugged ports on your carb?...My 76 C-20 with basically same carb has two more ports on front of carb plugged with rubber cap (one on pass side above fuel filter and one on drivers side close to mixture screw). Another thing to check is the real short little vacuum line from the choke dashpot to make sure it is not split or dried out and leaking. Your photo of pass side carb was too fuzzy to make out details but it looks like all your linkages are there.Regards,Henry