Im gonna change out the retainers on my 03 just to be safe. Is it really necessary to upgrade the springs also? I plan to make power in the upper 600s and rev to 9500. Im not boosted yet but I just wanna have all the right supporting mods before I do anything.
Thanks

 

Also some people say not to change the exhaust retainers but some people say to change them. What are your thoughts?

 

I would build the head entirely if I was planning on making that much power. Other than that, my car actually has an ap1 head on it now with JUST the retainers and locks upgraded to ap2

 

I have a stock ap1 head with ap2 intake retainers and locks/keepers. When upgrading ap1 heads to ap2 spec your only suppose to change the 8 intake retainers and keepers to ap2. But if you really want to rev over 9,000rpm you should just run stiffer aftermarket springs and titanium retainers. Stocks springs is only for stock redline.

 

i only changed out my intake retainers and keepers for the ap2 ones