Im finishing up the LT1 swap in my 87 IROC, and Im trying to connect the radiator hoses to my stock radiator. I've got it all figured out(I think) but I dont have another nipple for the overflow. Here's what I've got:

Hose off the thermostat to bottom fitting passenger side
Hose from other large port on water pump to top left hand fitting on radiator
Bottom two small ports on water pump blocked
Top small port is connected to "T" and goes back to the heater core
Small hose coming from steel line that wraps around the back of the heads to old overflow nipple.

Ok, that's what I have, you may not be able to understand everything Im talking about, Im not even sure that I do, but what the heck, that's the best I can do in describing it.

 

Connecting the steam vent line (from back of the heads) to the overflow nipple isn't going to work. Its going to be flowing against a cap held closed by the radiator pressure = no flow.

Have you tried posting this on either the 3rd Gen or LT1 Tech forums?

 

Very little comes out of the pipe from behind the heads. You can likely carefully add a fitting to your side tank. I have a griffen full aluminum rad. and I just added a trans drain setup to the top of one of the end tanks and it has not been a problem.

 

Go to thirdgen.org and look at the engine swap forum.. that said, for my swap I used a universal 31 x19 griffen radiator, I welded a 6an fitting to the side tank and ran a braided hose to the back hard line.. someone on thirdgen used an upper radiator hose with a connection that ran to the hardline on the heads though not sure of part number, but that allows you to run with a minimum of fuss..

My routing is as follows, hose off thermostat to upper connection on drivers side of radiator, bottom to bottom passenger side.. your routing crosses the hoses, I have no issues running my setup at all with a 160 thermostat the car runs nice a cool. My two lower connections go to the heater connections, it sounds like you are plugging your heater connections.. I have no extra fittings on the pump (it was a vette replacement) and run a meziere electric..

 

I think your water pump is quite different from mine. Because my thermostat housing points towards the passenger side, and the other large port to the driver side. Also, the bottom two should be the heater return connection, but Im keeping my stock return route so that should take care of that without problems. Let's hope. But I think i figured it out, see how this sounds. I kept it all the same as before except for the small steam vent line is now splice into the heator core return hose. This should work if my research is correct, but we'll just have to see I guess. Thanks everyone.