305 tbi me again...... still trying to figure out the water bypass thing for the vortec manifold that i already ordered. i read but i need pics of what they are talking about. my water pump does not look like what they describe. the one i have does have a plug in the (BACK) side of the water pump but not on the passanger side outlet. pictures would help of what it needs to look like. do i need a vortec water pump?? im almost there guys. please help me. "If you are using a 1996 or later Gen 1 Chevrolet block, then you must route a coolant by-pass line from the intake manifold to the water pump. The 1995 and earlier blocks are machined with the by-pass provision in the block. The by-pass line must run to the passenger's side outlet on the water pump using a 5/8" hose."

The loop through the heater core acts as your bypass. I didn't realize they had removed the bypass passage in later blocks, but it's not like it's a big deal- the hole is maybe 1/4" diameter at the most. Doesn't do much.

Little piece of reference- Big block Chevys often have a "bypass" line like you are describing since they never had a bypass passage cast into the block from the factory. Yet, there are many big block intakes that have no provisions for one. Including the old Vic Jr. I use on my 454. I figured the loop through the heater core accomplishes the same thing and I was right. It works just fine without it, hot or cold. No issues.

The whole point of the "bypass" is to allow coolant to circulate through the engine even when the thermostat is closed so the pump isn't cavitating against motionless water and so that "hot spots" don't form at various places in the engine before the stat opens.

In short, it's nothing to freak out too bad over. If you're the nervous type, drill 3-4 1/8" holes in your thermostat so that it's always got some amount of flow going past it.

Yes, the vortec block does not normally have the bypass port in the block. You must provide some sort of a bypass. The heater core is not a bypass. If your water pump does not have the port, then simple do as Damon said by drilling holes in the thermostat lip. I believe I used 2 hole 1/4" holes. Works fine.

ok but then im let with like 4 water ports without plugs left on the intake...what goes there??
just to make sure we are on the same page, im switching from the swirl ported tbi heads to vortec heads. the block is staying the same.
also did you have to fabricate your throttle bracket?? if you did, could you take some pics of it please. i would greatly appriciate that.

I have a 880 block, and it doesn't have the bypass for the water pump. Can I simply drill a bypass on the water pump pad? I have seen several 880s that have them, so I'm thinking there shouldn't be any issues there. Any thoughts?

If you are using your old block it is not an issue. Bypass is in the block.