QQ, I'm about to remove the intake manifold on my L98; do I need to drain coolant from the engine first? I don't think I do but I've never opened a Chevy engine so not 100% sure.

 

Yes, unless you don't care about coolant all over the engine, floor, etc.

 

In my 91, I put air compressor tank drain **** on each side of the block, them coupled with the drain in the radiator, what I do is remove the thermostat housing, then open the drain *****, when I see no coolant in the intake I close them. It usually takes about 1.5 gallons out and there is almost no oil contamination when the intake is removed. I have pretty much always worked on sbc this way, in your case you'll be removing knock sensor on the passenger side, and the oil cooler line on the driver side as well as removing the radiator cap, and opening the radiator drain to accomplish the same thing. If you end up with coolant contaminated oil, just finish the intake repair, fill with coolant and start, then once warm change the oil prior to driving it.

 

I drain the radiator, remove the thermostat housing and blow a shopvac into the thermostat housing for a few seconds to clear the coolant back into the radiator and lower in the block. Usually nothing more than a drip or two comes out when doing that.... It is easier to do everything on top then get under the car in my small garage.

 

Whew, glad I asked! Awesome advice, thanks a lot guys!