phatboy

if i do a 5.7 in my truck should i keep the stock 5.7 heads and intake or use the 5.3's ive heard a few different suggestions but no definate answers. which combo makes more horsepower, compression etc. truck is in my sig, 5.7 is out of a 2000 f-body. if i drop the complete motor in i assume my computer will work for this?

onebadrubi

You should already have a truck intake. Which provides more torque in low rpms. If you bore your truck to a 5.7l you may or may not want to use the ls6 or similiar manifold. The ls6 manifold will help you maintain power up high, 6000+rpms where as the truck intake will begin to not flow as well up above these rpms.

The heads on your truck FLOW the same as ls1 heads just increase compression. So I would leave your stock 5.3l heads on your 5.7. many ls1 cars do this just to increase comp for cheap.

Dirty 30

iTrader: (97)

the valves on the 5.3L are smaller and the smaller combustion chamber will bump compression to around 11:1
Im in the process of installing a 5.7L LS1 with an LS6 cam and stock 5.3L heads in my V6 truck. I plan on getting the heads ported with bigger valves later on so im not too worried about that HP loss or HP that could of been there.

06sierra5.3

iTrader: (7)

theres not really any room to increase valve size on a 5.3 head. i have a 5.3 i plan on porting the stock heads and using the sodium filled corvette exhuast valves (theyre the same size) and replacing the stock intake valves with titanium valves of the same size.

twobit

iTrader: (12)

I put z06 sodium filled exhaust valves in mine and also the bigger intake valve. Working good so far.