So im getting ready for a cam swap in my ls1 powered c5 this spring. I need to change the valve springs and would like to do so without removing the heads. in the past i've done this on blue ovals using the ol air-compressor. However those ford springs didnt have nearly the seat pressure of the 918's i will be running.
Does anyone know if the higher spring pressure presents a problem for replacing the springs this way or will the heads have to come off?

 

I did my 918's on my first setup useing the top dead center method. Roll the engine over untill the cylinder your working on is all the way up and let the pistion hold the valve. no head removal. This will help too.
http://www.ls1howto.com/index.php?article=23

 

the air compressor way is how i have done over 25 cam's on LSX motors so im gonna give you a 100% on that being enough the MORE tool is the **** by the way

 

+1 It was a little pricy but worked like a charm

 

The easiest and fastest tool to use is the Crane 99472-1. It does 2 springs at a time and it's easily done with the heads on.

http://www.cranecams.com/?show=brows...Number=99472-1

 

That thing is a turd. Breaks head bolts, strips out on the last spring (unless you dont want to buy another tool for every swap dont get it), and is very good at giving black eyes. Get the crane.

 

I always use TDC method, much easier and less time consuming than fighting to get the air fitting threaded in each plug hole.

Little tip. Before removing the old/factory valve springs, take a 5/8 plug socket and put it on top of the retainer on each spring. Give it a light wack with the hammer, it'll loosen the locks. If you don't do this, sometimes the locks won't come apart with the spring is compressed. This trick makes life a lot easier

 

Too bad that won't work with L92/LS3 Heads..

 

According to Vinci, they have a version that works on the LS3/L92.

http://www.vincihighperformance.com/...NT%20PAGE.HTML

The Crane Valve spring tool for the LS3/L92 is part number 99475-1