So you took that spacer out, meaning the one shown in the picture above, parked it on the upper fan shroud for the radiator as shown in pne of the pictures that you posted, and re-installed the carburetor with nothing between it's base plate and the flange on the manifold?????
First of all, what is hanging off that bolt is some of the threads from the hole into which it was inserted. You are correct in believing that you bottomed the bolt before it could tighten up. The consequence, what you call the bolt spinning freely, means that the threads in the hole have been torn free and that is those strings of wire hanging off the bolt in that picture. Those bolt holes are not through drilled, they are blind, and the bottom 1/16th or so of the hole has no thread cut in it. Without that spacer, your bolt was too long.
That spacer needs to be returned back to being in between the carb and the manifold. It has the dual purpose of being the gasket that seals against the machined surfaces of the carburetor's base plate and the manifold and it also acts as an insulator to deflect some of the heat coming off the manifold from reaching the carburetor and adversely affecting it's operation. Without that spacer being in place what you have is metal to metal contact and the ports and passages machined into the carb's base plate are wide open to the air movement generated by the motor when running. It is possible that you could get away with using just a thin gasket; they are available as such from most indie or franchise speed shops but there has to be a gasket present between the two machined surfaces. This isn't Germany and the quality and precision of the machined surfaces is not so fine and precise that using gaskets can be ignored.
Before doing anything else, you need to make a trip to the parts store and score at least one new one and preferably two. (Heir and Spare). You also need to acquire a good HSS bottoming tap in the thread pitch and proper diameter for the hole that that bolt was removed from and run it down the hole to see if you have any threads left to use. ARP actually makes a chasing tap set that is strictly for chasing and cleaning threads; they do not cut new thread and are just slightly smaller in diameter so they do not shave down the existing thread, but they only come in coarse pitch, to the best of my knowledge.
There is, roughly, only about an inch of thread or less machined into that hole. Worst comes to worst, it will require that you get a thread-sert kit for it and, following the instructions, to oversize the hole and then tap it using the included tap to create a new opening into which you will then insert the new S/S wire thread using the insertion tool. Unless that manifold is aluminum, which will make the drilling easier, whatever size of drill bit that the kit advises you to use needs to be a High Speed Steel bit. CS or carbon steel bits can, will, and do break, usually at the worst possible time and in the nastiest of locations.
The repair work can be done in situ, just be sure to stuff rags or shop towels down all the intake ports in the carb before you start the repair, Use compressed air, even a couple of those air in a can deals that the computer shops offer to clean the keyboards, to clean out the hole and blow away all the debris, cuttings and general crud BEFORE you remove the towels from the ports, and remove them SLOWLY to make sure nothing caught by them gets a chance to escape and fall down into the runners. Even the finest and smallest of shavings making the acquaintance of a piston or valve can ruin your day permanently.
As for that bolt, lose it and score a replacement with clean thread. It is only either a grade 2 or possibly a grade 5. It will need to be an exact match for length or slightly shorter. NOT any Longer.
Nick
