3x00 heater lines

[ericjon262]

just to make sure I'm right, the heater lines are as follows:

line at the thermostat goes to the core, and the line on the tree comes from the core.

Right?

[caffeine]

When I asked that question during my swap I was told it doesn't matter which direction it flows. I think I had the line closest to the trunk side head go to the heater core line that comes out at the stock dog-bone mount location an my heat works fine.

[ericjon262]

When I asked that question during my swap I was told it doesn't matter which direction it flows. I think I had the line closest to the trunk side head go to the heater core line that comes out at the stock dog-bone mount location an my heat works fine.

I understand that it doesn't matter a whole lot, but the main reason I was asking, it because one line to the core is wrapped in insulation, and the other is open. I'd prefer the tube going to the core be the one with the insulation.

[Johns88FieroGT]

Since this thread is a month old, I don't know if you're still looking for an answer, but on a 3400 the line hooked to the tree should be the return line. It's on the suction side of the water pump. So the line coming from the T-stat is going to the core. I assume the 3500 is similar, but we all know about assuming.

I only know that because I spent some time figuring it out so I knew how to plumb the heater line in my Fiero 3400 swap. I have an '88, with only one heater line attaching to the engine (the other tee's into the passenger side coolant tube) so I wanted to make sure I had the right one. I attached the lone heater line to the T-stat housing and so far, my heater seems to work correctly, although I've only had the engine running about 1 hour total since the swap (still waiting on tuning).

John

[ericjon262]

cool, thanks for the info. got a build thread or pics of your swap?

[Johns88FieroGT]

I was planning a build thread on PFF, but I've started & stopped working on it so many times I didn't want to start a thread until I was sure I'd actually finish. Finally committed to finish it a few months ago but haven't had the time to post anything yet. I took pics as I did the build, so I'll still be able to do it. Soon...