i have my stock heads on, with the compression up to about 11.1 (0.050 milled) if i go to a ported 5.3 head (not milled any), how much will that litle less compression play in total hp gain? i have not touched the ports on the stock ones at all, just milled.

i figure i gained about 10 hp? by milling them that much. stock 5.3s are like 10.5 right? so im looking to loose about 5? but then gain it back in porting. so maybe a total gain of 20? not sure, looking for some answers <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

Don't know exactly how much HP is on the table by reducing your CR, but a set of TEA 5.3 heads will give you a 63cc chamber. Thats about 10.7 to 10.8 to 1 CR.

In reality, they will mill them a mere .003" to insure flatness and surface correctness. Also, a little material is removed from the chambers to unshroud the valve.

As I stated above, with this all said and done, you get close to a 63cc chamber and between 10.7 and 10.8 to 1 CR.

Of course milling more can bump the CR ratio above 11 to 1. The nice thing about this is that the 5.3 heads don't need as deep of a cut to get you the CR the 5.7 heads do (we all know that). Nice if you may have piston/valve clearance problems associated with big duration.

Ron,