new 604 heads

[daddyb18]

Can someone who knows, by flow or dyno numbers tell if the latest heads for the 604 are better than the previous ones. I have heard they are about 15 horsepower better, but you know how people talk.

[Steve_Hendren]

Here is what I posted on our FB page a few months ago.
Hendren Racing Engines
18 November 2013
*** FYI *** I get asked daily if the "new" 604 head's are better than the "old" 604 heads. The answer is....They are the EXACT same as the heads made from mid 2007 until now. The ONLY difference is the "old" head's were engraved with GM Performance Parts, and the "new" head's are engraved with a Bow-ti emblem. Other than that, they are the EXACT same cylinder head. If anyone is telling you differently, then they are simply trying to sell you something that you might already own. Trust me, the Bow-ti emblem is not worth another 10hp!! Hope this piece of information helps save someone from spending money that they do not need to spend.

[brad hibbard]

I concur with Steve completely with the power gains between the heads

I will say that the valve job on the new heads is nicer than the older heads from factory but it does not equate to any noticable power gains unless the seal is lost between valve and seat--------but with that said an older head can be sent to Hendren's and have a CnC GM Blueprinted valve job done (100% completely GM legal) and then be exactly the same as the newer heads--- which is what we do with our older heads

myself and many others get caught up in the fact that the appearance is better---- first of all they are new and should look better
secondly, different foudries and machine shops will have different appearances----and this stuff is built in different foundies BUT has always been built to the GM specification which has NOT changed
so at the end of the day it might look a little different but its gonna run down the straight away the same

Brad

https://www.race-1.com