I have a set of heads with 2.02 intakes and 1.60 exhaust valves.

Can I use these on a 305? I've been told you can't use the "big" valve heads on a 305 but I wanted to see if folks here had used them successfully

Thanks.

 

Depends on both the heads and the block.

Think about it.... the 305 bore is 3.736".

2.02" + 1.6" = 3.62".

3.736" - 3.62" = .116" (less than 1/8") and don't forget that part of that .116" is consumed by the space between the valves.

How much margin for error does that leave? Given production tolerances that I've seen, especially on blocks from the 70s, that doesn't inspire a great deal of confidence.

You can tell AT LEAST about the heads, if the valves happen to land inside a 305 head gasket, by a significant margin; you have a prayer. Lay a 305 head gasket on the heads, use a couple of drill bits or something to simulate the dowel pins; then lay the same gaskets on your block; and see if you get lucky, and the valves are actually WITHIN the cylinders, and won't just smack into the deck when they try to open.

On the other hand, what good does a large valve do, if the edge of it is RIGHT UP AGAINST the vertical surface of the bore? Does it matter how big the valve is (diameter) or how far you can open it or hold it open (cam) if all the air has to pass through some arbitrarily small crack between the valve and the bore?

So yeah, MAYBE you "can" use them; but whether it's a "good idea" or not, is another matter entirely. As is so often the case, just because a thing "can be" done, doesn't automatically mean that it "should be" done.