360 Magnum building on an existing bottom end

65TTCuda said

Do they perform well OOTB ? What kind of HP do you estimate your engine is producing ? Do you think these heads can support 500+ HP ? Did you buy them bear and build them to your cams needs or buy them all assemble ? What cam are you using? Thanks in advance for the info.

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I’m not going to answer the question to him but instead give you an in general answer to a question you asked.

The head OOTB is a good performer. (As long as it checks out OK with hood valve sealing) Achieving 500 hp is possible but you may not like the way it has to be done since the head flow and capacity is limited being a street/performance head. It would require a good bit of compression to support a relatively large camshaft pushing the heads intended use. It’s usable range would be narrow and at a very high rpm. This is why people port the head. It offers a greater amount of flow and volume of air and fuel for more power.

500 HP is a good bit of power for a small block. It’s really not a throw together engine.