Search engines don't base their rankings on font size. If you use a <h1> tag for your title, you can use CSS to make the size of the <h1> tag look normal. Just put this line in your css file:
h1 {font-size: 12px;}
(or use whatever font size you want).
24pt text is not only ugly, it won't do anything for you!
You can surround the product title with an <h1> tag if you really want.