1. Is my old radiator, or a new 2.8 radiator, going to be sufficient to cool the 3.4?
Yes, the radiator replace it with new or have a good radiator shop clean it.
2. Where could the water be going? It doesn't appear to be leaking from anywhere but the over flow cap (little spout) when up to operating temp.
Make sure the system is properly burped, fill with coolant. Allow engine to warm up with radiator cap off. When thermostat opens, top off with more coolant.
Make sure the overflow tank hoses are properly connected. Hose from radiator goes to the top of overflow barb with the pickup tube sticking in coolant. Other hose is overflow it goes toward the ground. <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> Dont ask how I learned this ... It wasn't my doing.
3. Will my 2.8 heads work on this engine (3.4)?
I dunno, as long as the 3.4 is good don't sweat it.
4. Will electric fans be a better choice instead of buying a new fan clutch?
When my truck starts up cold it really roars,when up to temp hte clutch releases. If the truck gets hot, raise the hood while running yo should feel plenty of airflow. If you still can't tell for sure. Turn the engine off. Grab the fan under the hood you should feel some resistance. I stll use a cleaned factory radiator and clutch fan.
5. Is it useless to put a 4.3 TBI without boring the intake?
Pretty much. It can be done after swap. Remove the 2.8 TBI, take rags soaked in motor oil, pack the rags down in the intake manifold. The theory is the rags will catch the aluminum shaving. Before removing the rags run a good strong shop vacuum around the intake manifold, to suck up all the loose stuff. Carefully remove rags, repeat with the shop vacuum. If you have any doubt about aluminum shaving falling into the motor. Remove the intake manifold. Do not start the truck.
