I clay tested my .30 5.7's to check my P/V, and sure enough they hit, so Im exchanging them for 5.3 heads. My question here is: Do the 5.3's flow as good as the 5.7's? Are there any advantages with either?

 

I have read the 5.3's flow better than the 5.7's.

 

Have you considered thicker head gaskets instead? Seems like that would be the cheapest solution, if you could make it work. You said the valve just barely touched the top of the piston, right?

 

I thought about it, but two things come to mind. (1) It's not going to cost me anything to swap them, bought them from raging motorsports and Mark is a great guy. (2) Dont want to loose ANY compression. Now that im getting 5.3 heads, I'm looking foward to 11.1 compression.

 

I would go with the 5.3's, don't forget to open the chambers up to 3.900" (like our CNC'ed heads). The 5.3 flow better on exhaust only if the chamber is reshaped properly,(as we do on our CNC), otherwise they will flow less due to valve shrouding. Hope this helps, Mark can help you with all this

 

What cam are you going with that caused your valves to hit? I am keeping my 5.7L heads and only had them milled to .020 because I was paranoid about P/V clearance.

 

The cam IS a custom grind that I chose to make, specs are: 228/236 .572.602 111LSA with 2 degrees of advanced ground in. Nice healthy cam :p

 

5.3s flow worse as is, yet with a port job they can flow as good as 5.7's, stock they also come with smaller valves but i am sure that will be taken care of. The largest benefit of 5.3 liter heads is that you can mill them more than the 5.7's and ls6 heads, while keeping p/v clearance.