243 heads on my 5.3 07
 

Hey guys so I'm having alot of doubts....I bought some ls6/799 heads off a 5.3 08 silverado I wanna know Is the HP gain good? Also how bad is the gas mileage drop? And last question is there a difference in sound as far as being louder?...help is very much appreciated

The heads will need to be shaved .030 in order to keep your current compression ratio. You'll more than likely see a little bit more fuel mileage. You cam will really enjoy the extra airflow.

Won't be a bad idea to think about a retune as well.

no difference in sound... as said above, youll need to mill them to keep your currnet compression ratio the same

The guy I got em from did a good job with milling them and clean em up real good and definetly doing a retune what do yal think as far as HP gain?....I might go from 3.23 gears to 3.73 as well just dont no yet

maybe 20-30 hp gain

Thats what I'm betting on....I got a friend installing em for about 200 so will see soon lop thanks for the help guys....any word on if its a good idea to switch gear ratio to 3.73

3.73 will wake it up bro, or step up one and do a 3.90. . those heads will help that cam breath some more!

i would say 25-35 hp gains with milled heads bro as far as i know

the thing stopping me from switching to 3.73 is I've heard that switching gears makes the truck shake at 100+ so I've heard??

Only if the gears are not installed right (backlash)