The LS4 engine is from a 2006 Chevy Impala with 7 miles on the odometer. We decided to increase it's output by doing the following mods.
The following photos were taken just after cam and lifter installation. The LS4 block accepts any standard LSx cam. ARP head studs have also been installed. The engine has not been cleaned, it's just that new!
Below is a picture of a DOD/AFM lifter on the left and a non-DOD lifter on the right. Despite the taller appearnace of the DOD lifters, they use the same length pushrods. Although the stock lifters would likely work with the new cam, we chose to install a set of GMPP 8000 RPM lightweight race lifters. The new lifters also required new guides. Our combination of cam, lifters, and shaved heads required shorter pushrods, so I installed a set of Comp Magnum one piece chromoly pushrods.
We decided to eliminate the DOD system completely. The LS4 valley cover contains the solenoids and manifold to deactivate the DOD cylinders. Although the lifters will operate normally with the solenoids disconnected, I replaced them with an LS2 valley cover which is lighter and provides the clearance required for the intake manifold.
The cylinder heads are the same '243 castings that are used on the LS6 and LS2 engines (LS6 has sodium-filled valves). I had the heads milled .035" to reduce the combustion chamber volume from 65cc to 60cc which will raise the compression ratio to 10.6:1. The picture below shows one head after milling and deburring.
The cam kit came with the blue LS6 valve springs shown below.
The heads were installed using GM gaskets and ARP studs.
The LS4 intake manifold has a fairly small throttle body, and necks down to a D shape just inside the openning to provide clearance for the oil pressure sensor. We chose to use an LS2 intake along with it's throttle body, injectors, and fuel rails.
Above: LS2 on top of LS4
Below: LS2 on right
Because the intake manifold will be installed backwards of what GM intended, the oil pressure sender port needed to be modified. The boss was cut off flush, and a new boss welded on at an angle to provide clearance for the throttle body.
I did some deburring and smoothing of the stock exhaust manifolds before sending them to Jet-Hot for Sterling ceramic coating. The coating doesn't have a large direct effect on performance, but it will lower the underhood temps substantially.