Originally Posted by Scandinavian
Hey! Chevrolet SB generation2 Cylinder heads do they fit on a generation1 block? i found some Aluminium cylinder heads at work and they looked really similar to the gen1 heads! except some wather crossovers in the back!
i dont remember the numbers but it ha 2inch intake 1.6 ex175cc intake runner Thant's all i remember i ve got the numbers on a paper in my garage! it was from a 96 camaro!
Gen 2 heads will bolt to a Gen 1 block but the coolant passages around cylinders 1 and 7, 2 and 8 will not match the block leaving a coolant leakage path into the valley. Additionally, there are no coolant return passages that mate with a Gen 1 intake manifold while the Gen II intake manifold, GMPP part for a carb, has no coolant return.
At the upper ends of the Gen II head is are the intake holes that mate with the incoming coolant from the pump that enters the block and is immediately rerouted up into the head which then flows from the head down into the block and returns from the front under the inlet passage and back into the pump housing. These are the holes that overlap the valley when this head is put on a GEN I block. These holes can be plugged with weld, I prefer to make an aluminum lozenge that is welded in rather than fill this large hole with weld but either way will work. The head is then milled flat and a smaller hole drilled in the filled area that matches a Gen I head gasket. This plugs the leak path to the valley. This can't be done with a gasket along as over the counter gaskets can't make a seal unless these particular holes are filled. Epoxy could be used but I wouldn't trust to its long term ability to maintain a tight seal through heating and cooling cycles. Also, while a conventional coolant return can be fabricated into the head so a conventional manifold can be used this is a bog effort on odd shaped passages in the cooling jacket making it difficult to do. I prefer to bore a 1 inch hole on one facing end of the head where the vent tube fastened. Then install a 1 inch to #16 AN fitting, route up to a remote thermostat housing than back to the radiator with a conventional return nipple and hose.
While this was common to do back in the 1990's before everybody on the planet was making Chevy performance heads and the GMPP Vortec and Fastburn heads were still relatively unknown today there are simpler and less shop intensive options. To modify a set of GEN II heads on top of the cost of rebuilding them, plus purchasing a GMPP GEN II to carb intake is substantially expensive, comparative to the cost of a performance set of aftermarket modern heads.
I still run a set of GEN IIs on my 350 powered S15 which I built about 10 years ago. But I had the advantage of parts from other projects laying around and the tools, equipment and expertise to modify them myself or access to people with that stuff so cost was not an issue, other than that there is little to recommend going through this process.