Rage

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.

respectirocz

does the stock radiatoir have a provision right under the cap for the overflow bottle?

Rage

Indeed it does, but I put the steam pipe connection there, not thinking, and that's not going to work, so my main concern as of this point is where do I put the steam pipe connector?

respectirocz

i'm not fully following which connection you are refering to, the external cooling lines with the steam vent? or does this line come off the water pump?

respectirocz

i took a look at my waterpump, the way i planned to run the lines was one hose from the water outlet after the thermostat to the top of the radiator and then the bottom of the radiator to the inlet, and the two smaller lines running to my heater core with a control valve splice in

Dave89IROC

use a upper rad hose from a 95 Z28, it will have a 3/8 hose "T"ed into it, put the steam line there

Rage

Right, and I have that one but it's on the driver side of the car. Although it would work if that hose was straight, then I could splice it to the heater hose that goes to the firewall.

Rage

Im refering to the external steam vent. It's the one that goes around the back of the heads and returns to the radiator. Here is what I have going from the stock radiator. On the driver side of my radiator is one big hole at the top, I have connected that to the large port on top of my water pump and there is a smaller 3/8 line that connects to the throttle body. On the passenger side, there is the overflow valve right below the cap, it is now connected to my overflow tank, below that, there is a 1" hole which runs straight back to my firewall and serves as a return for my heater core. And at the bottom of the radiator is another large port that connects to my thermostat housing. On the water pump itself, I have plugged both of the small lower ports and making my own route for the heater core. Now, off the 1" hole on the passenger side(which should be the heater core return) I have spliced in the 3/8 steam vent line. on the 94 and I believe 93 LT1 there is a large "T" atop the waterpump, has a large bleeder valve on it, that connects to a few different things. It runs off the water pump to the T, one side of the T is connected to the passenger side of the throttle body, and the other is the feed to the heater core. I hope all of this makes sense. Let me know if there is a flaw in that, cause I have'nt cranked my car yet, but I want to make sure I got it right.

respectirocz

i dont know where this 1 inch holes for your heater core return is, and i dont know how ur heater core is fed

i dont know why u would feed the thermostat housing to the bottom of the radiator
the thermostat opens when it is warm enough and the fluid comming out needs to be cooled
the fluid that needs to be cooled should go to the top of the radiator unless i'm mistaken, because thats where the thermostat housing would go if it were a gen I SBC

if i understand you on that, i think u have it backwards

as for the extrenal cooling lines from the cylinder heads
they go directly to the passenger side of the throttle body

i am not sure where the drivers side of the throttle body connects to

and like i said in my previous post, i was planning on using the smaller pipes on the water pump for my heater core feed and return, with a control valve on the feed

Dave89IROC

that is how LT1s are, they are reverse flow

here is how I have the one in my K5 run


thermostat to lower pass side of rad
other large w/p hole to top drivers side of rad
both heater hoses to the two tubes on the pass side of w/p
then the steam tube is to a reducer and hooked to the heater hose nipple on the rad
the overflow is hooked up normal

Rage

LT1 Coolant Flow:

The LT1 is completely different since it uses reverse flow cooling. The incoming coolant first encounters the thermostat, which now acts both on the inlet and outlet sides of the system. Depending on the engine coolant temperature, cold coolant from the radiator is carefully metered into the engine. This allows a more controlled amount of cold coolant to enter, which immediately mixes with the bypass coolant already flowing. This virtually eliminates the thermal shock present in the old system.

After entering through one side of the 2-way thermostat (at the appropriate temperature), the cold coolant is routed directly to the cylinder heads first, where the combustion chambers, spark plugs and exhaust ports are cooled. Then the heated coolant returns to the engine block and circulates around the cylinder barrels. The hot coolant from the block re-enters the water pump, and hits the other side of the 2-way thermostat, where it is either re-circulated back through the engine or directed to the radiator, depending on temperature.

All of this means that the thermostat housing is the INLET (opposite of most engines), while the water pump is the OUTLET. The water pump (outlet) on the engine runs to the top left (inlet) of the radiator. The lower right (outlet) of the radiator runs to the thermostat housing (inlet) on the engine.

This also means that the "upper" hose on the radiator would be connected to the water pump (mid/lower part of the engine) and is the outlet of the engine, so it should be hot with the thermostat open. The lower hose on the radiator is connected to the thermostat housing (upper part of the engine) and is the inlet to the engine.

The main concept behind reverse flow cooling is to cool the heads first, which greatly reduces the tendency for detonation, and is the primary reason that the LT1 can run 10.5 to 1 compression and fairly significant ignition advance on modern lead-free gasoline. Reverse flow cooling is THE KEY to the Generation II LT1s increased power, durability, and reliability over the first generation smallblock engine.

There are three main circulation systems for the LT1, while most engines only have two systems. As with most cars there is circulation through the heater core and the radiator, but there is a third system on the LT1 which includes steam vents in the head, along with a pressurized reservoir.

Coolant to the heater core comes from the water pump. The lower hose on the water pump is the heater core inlet, and should have a flow restrictor mounted in the hose. This is to prevent over-stressing the core at high engine rpms. The heater core outlet hose returns to the water pump at the upper hose connection, and also has a T-connector to the pressurized reservoir to bleed off any air.

This Article is not my own, it was written by Scott Mueller.

http://www.theherd.com/articles/lt1_cool.html