The old intake manifold gaskets dont have this water port blocked off, but the new one does. These new fel-pro intake manifold came from autozone in a head set "HS 8510 PT 4". Autozone and fel-pro's website, and the head set gasket box shows that they made these intake manifold gaskets to fit my 89 Firebird's 305. I did change the intake manifold, carb and distributor but that shouldnt make a difference. Anyway enough with the blah, with these intake manifold gaskets I'm blocking water from flowing through two ports Does anyone know how big of a difference that this is going to make? here is a pic of what they look like, the old ones just had an open port.

There is no cross flow of coolant at the rear of the heads. Just orient the gaskets so the blocked ports are at the rear.

Since you evidently went to carb, the intak you used may or may not have a coolant hose bibb at the RR of the engine. In that case, you would need to punch the gasket to allow flow.

Its already back on there unpunched, they are at the rear. The only thing I can tell you about this intake manifold is that its an aluminum intake manifold with the GM logo on it. Aside from that here is a pic. Let me know if leaving them like this is going to cause any major problem. Thanx, appreciate the help.

The example in the attached image in your first post shows an intake with a heater hose outlet at the right rear corner. If your intake has a hose connection at the RR, you will need to punch a hole through the gasket at that location. If there is no hose connection, don't bother. TPIs have no such hose, which is why the TPI intake gaskets have no hole in the gasket.

krap, the image didnt show. This one is the one that I have. There is a heater hose at the front passenger side, and its kinda small put there is a hole at the rear, but its plugged.

what was gm thinking? the pictured intake is #14101074 used on '87 and up carbed v8s. i own one i pulled off a truck (non-stock application). i recently ran into an '87 LG4 at a junk yard that i tried to figure the hose routing. the fitting at the right rear is 1/4 inch NPT, but some of the hoses were cut off so i don't know where it went. and it had a heater hose fitting at the front going into a vacuum controlled on/off valve. so at least one of the rear intake water passages would have to be open for the fitting to be there. but if the fitting is just plugged and the rear water passages were blocked then you would have air trapped back there and would the pressure from the water heating and the pump want to blow through the gasket? also , what if both water passages were open? i've been told that the sbc water pumps create higher pressure on the passenger side so maybe water would flow from one head to the other. what was gm thinking when they put a water passage in the back of the intake? they went 30 years without one.
does anyone have an '87 LG4 they would be kind enough to diagram the water hoses? i'm assuming both rear passages are open. can anyone verify this?