Hot coolant flows both through the inlet manifold, and out of the cylinder head. From the cylinder head, it travels to the control valve for the heater, through the heater matrix etc and then back out on the other side. From there, it combines with the hot coolant that has passed through the inlet manifold, and returns underneath the exhaust manifold towards the water pump/radiator.
The odd inlet manifold I have for the single carb has something sticking out of the top of it at the back, which is currently blanked off with some tubing. The 1500 manifolds I've seen have it at the front, though I imagine its the same thing. Is it some sort of breather that isn't needed for UK spec? It also has two seperate T pieces further down the line from the end of the manifold, which each have one way blocked off in a similar fashion, so I don't know what (if anything) should be attached to them.
Now, I'm interested in using a 1500 manifold, which again, complicates matters further...
The early MkIII/IV manifolds I've seen have a single connection on the exit of the inlet manifold for the coolant, which would presumably fit into the top of the return water pipe, with the heater return attaching just after it.
However, the 1500's (and later MkIV's?) have a connection at the top and the bottom at the end of the manifold. Presumably, the the bottom attaches to (the second?) connection on the return water pipe, and the return from the heater attaches to the first. That leaves the top hose connection on the inlet manifold... the only thing I can guess at without being a bit more informed, is that the inlet for the heater/valve comes from the output of the manifold as opposed to directly from the cylinder head.
That leaves the question about what I would do with that connection, as it has nowhere to go on mine if I were to install a 1500 manifold to an early MkIV - the obvious answer seems to blank it off, though I could always have a T piece to combine the outlet from the cylinder head with the outlet from the inlet manifold, but there doesn't seem to be a whole lot of point.
Slightly off topic, but does the inlet manifold bolt to the exhaust manifold? I've got some (completely rusted) holes in the exhaust manifold, but the inlet is much smaller, so it is far from reaching, and I imagine not that big an issue, when you consider the sports exhausts etc don't have anything available for that.
Wow, I'm sorry for writing all that, I hope you can just about follow it... I imagine I've answered most of my own questions, but I've no idea if I've got them right or not, hence the post
Many thanks in advance for taking the time to go through all this and answer my
questions!
