OK – I have a curious question. I am replacing the head gaskets on my 1987 Firebird with a 2.8 L V6.
Unfortunately I have already thrown away the old gaskets. On the new gaskets – the water jackets line up perfectly between the gasket and the head – however, the water jackets does not line up perfectly on the block… How is this possible? On the front side of the engine – it actually blocks off one of the water jackets.
This is the second set of gaskets and the same issue. This is the heads that came off of this block. I took the heads back off because after the initial bill, it seemed to be running hot. In hindsight, I might not have bled the cooling system properly. But I want to verify this head gasket situation as correct before I proceeded. There are no markings such as top, front, etc. on the gaskets – so they seem to be nondirectional.

 

Just because there's a hole in the block deck, doesn't mean it's a passage for water flow.

Very little heat needs to be removed from the block, compared to the heads. But the heads even have places where there's very little heat... the intake ports for example. OTOH the exhaust ports are the hottest piece of casting in the whole motor among all the parts that have coolant in them. The gaskets are designed to "meter" the water to where it is needed.



As an example, here's the gasket for a 400 V8. Very similar to 305/350 except for the holes in the green rectangles. In this gasket, the yellow holes are the bolts; the white ones are oil drainback; and the red ones are the dowel pins. All the others are coolant passages.

The 3 in the magenta rectangle are the most critical in that kind of motor: they are right under the 2 exhaust ports that are nearly joined together in the center. Note that there are basically none across the top of the photo except for 2 in the middle that also direct water to those 2 exh ports: that's the intake side. No heat up there. The other 2 exh ports are out at the end across the bottom: note how that's where the rest of the holes are.

I can assure you, quite a few of those little ones (1/8" or so) are sitting on top of holes in the block that are MUCH larger; some as large as near an inch and a half. Those are large so that casting sand can escape at the end of the mfg process.

I don't know in any detail at all how the coolant passages are designed in that 6-cyl, but you may be sure, they're similar in principle to the V8. Your engine is mass-produced: it's the same as every other one of those. Likewise the head gaskets are mass-produced: every one the same, made just for that one purpose. The holes in them are correct for the application. If they cover a hole in the block, then water isn't meant to flow there. In fact you may well find that there's no hole in the head at all to line up with them... IOW it wouldn't matter whether the gasket has a hole or not, there's no hole on the other side of it.

Lay the gasket on the block with the writing facing the head. (part #, mfr name, etc.) They are the same left-to-right (since the heads are the same), but not front-to-rear. The front of the left gasket is the same as the rear of the right one.

 

Thank you very much- that is VERY helpful