Isn't this akin to "intellectual property" theft?
This is what makes the performance business pretty tough.
Morally you would likely say that copying the heads isn't right.
But unless the heads we're protected via either trademark, copyright or patent protection there is nothing illegal about this.
The only way trademark protection would apply in this case would be if there was something about the particular shape of the heads that had been trademarked, like the shape of a Coke bottle. This kind of protection typically isn't going to help a performance product, other than keeping some one from marketing a product with your name and logos.
Copyrights probably aren't going to help you with a part like a cylinder head, you can copyright a particular shape of port for example but any slight modification of that shape won't be violating that copyright so its easy to get around this kind of protection.
This leaves patents as the only useful protection against outright copying of a part. Unfortunately patents are both time consuming and costly to acquire and also time consuming and costly to enforce, often the attorneys are the only ones make any money through patents.
If your company and product market are a big enough to afford a full time patent attorney on staff then you might be able to get some protection from patents, but this typically isn't the case for performance products.
So unfortunately in the racing marketplace most companies don't have a practical way to keep their products from being outright copied, its not fair but its just something you have to accept and manage if you are going to play the game.