<div class='post-body entry-content'>
<data:post.body/>
<div style='clear: both;'/> <!-- clear for photos floats -->
</div>
Substitua por este:
<div class='post-body entry-content'>
<b:if cond='data:blog.pageType != "item"'>
<b:if cond='data:blog.pageType != "static_page"'>
<div expr:id='"summary" + data:post.id'><data:post.body/></div>
<script type='text/javascript'>createSummaryAndThumb("summary<data:post.id/>");</script>
<span id='showlink'><a expr:href='data:post.url'>Leia Mais ►</a></span>
</b:if></b:if>
<b:if cond='data:blog.pageType == "item"'>
<data:post.body/></b:if>
<b:if cond='data:blog.pageType == "static_page"'><data:post.body/>
</b:if>
<div style='clear: both;'/> <!-- clear for photos floats -->
</div>
Agora procure por:
]]></b:skin>
E depois dele cole o próximo código:
<script type='text/javascript'>
var thumbnail_mode = "float" ;
summary_noimg = 450;
summary_img = 400;
img_thumb_height = 100;
img_thumb_width = 100;
</script>
<script type='text/javascript'>
//<![CDATA[
function removeHtmlTag(strx,chop){
if(strx.indexOf("<")!=-1)
{var s = strx.split("<");
for(var i=0;i<s.length;i++){
if(s[i].indexOf(">")!=-1){
s[i] = s[i].substring(s[i].indexOf(">")+1,s[i].length);} }
strx = s.join(""); }
chop = (chop < strx.length-1) ? chop : strx.length-2;
while(strx.charAt(chop-1)!=' ' && strx.indexOf(' ',chop)!=-1) chop++;
strx = strx.substring(0,chop-1);
return strx+'...'; }
function createSummaryAndThumb(pID){
var div = document.getElementById(pID);
var imgtag = "";
var img = div.getElementsByTagName("img");
var summ = summary_noimg;
if(img.length>=1) {
if(thumbnail_mode == "float") {
imgtag = '<span style="float:left; padding:0px 10px 5px 0px;"><img src="'+img[0].src+'" width="'+img_thumb_width+'px" height="'+img_thumb_height+'px"/></span>';
summ = summary_img;
} else {
imgtag = '<div style="padding:5px" align="center"><img style="max-width:'+img_thumb_width+'px; max-height:'+img_thumb_height+'px;" src="'+img[0].src+'" /></div>';
summ = summary_img;
}}var summary = imgtag + '<div>' + removeHtmlTag(div.innerHTML,summ) + '</div>';
div.innerHTML = summary;}
//]]>
</script>
Códigos na cor verde tamanho da imagem
Código em rosa quantidade de letras
Fonte: http://templateseacessorios.blogspot.com