archive.php

<?php
/**
 * Grid Content
 * Change the number of words in excerpt if in the grid loop
 */
function be_grid_content() {

	// First, we make sure we're in the grid loop.
	if( ! apply_filters( 'is_genesis_grid_loop', false ) )
		return;

	// Change length if teaser
	if( in_array( 'teaser', get_post_class() ) )
		$length = 20;
	else
		$length = 55;

	echo '<p>' . wp_trim_words( get_the_excerpt(), $length ) . '</p>';
	// Remove default content so we don't get both
	remove_action( 'genesis_post_content', 'genesis_do_post_content' ); // For Genesis 1.x
	remove_action( 'genesis_entry_content', 'genesis_do_post_content' ); // For Genesis 2.x
}
add_action( 'genesis_post_content', 'be_grid_content', 9 ); // for Genesis 1.x
add_action( 'genesis_entry_content', 'be_grid_content', 9 ); // For Genesis 2.x