meta_query where the meta value is not the post title

I found a solution that works (thanks Steve), hopefully somebody will find this useful in the future

$sql = "SELECT p.ID FROM wp_posts AS p
  WHERE post_parent = $post->ID
  AND post_type="post_type"
  AND ID IN (
   SELECT post_id FROM wp_postmeta AS pm
     WHERE pm.meta_key = 'my_acf_key'
     AND pm.meta_value = p.post_title
);";

$idList = $wpdb->get_col( $sql );