Making 750 Horsepower
This is the point of no return the for LB7's. How the tuner programmed the vehicle and how the owner operates the vehicle will determine if the rods can support 750 horsepower and for how long. Most whom we have talked to (and my personal opinion) say to absolutely change the rods if you want 750 horsepower or more (probably safer to do it around 700 hp).
While in the motor there are a few components to look at upgrading as well. Connected to the rods are the pistons. There are many good aftermarket pistons and each has its strengths and weaknesses. Make sure and discuss your objectives with each manufacture and see what they would recommend for your project. When it comes to compression, they will leave it up to you and your engine builder. "We have actually been seeing a trend of people lowering the compression of their high horsepower engines, but not to what most people would think," says Chad Remakel from Empire Diesel Performance. "Ten years ago, heck, even five years ago, most engines were being lowered down to between 12:1 to 14:1, but the recent trend with these engines is to lower it down to between 15:1 to 16.5:1."
Once the pistons and rods have been chosen, the next major item to think about is the cam. The factory cam can and will work in a 750 horsepower application. But there are few better times to think about sending the cam out and have a regrind done. This is especially important when trying to reach higher horsepower goals later.
While the cam helps valve lift, porting and polishing the cylinder heads can help reduce boost pressure, increase flow and reduce EGT's; which all equate to higher horsepower. "Our Stage 1 CNC Ported Heads really offer a good increase in flow and are a great option for the budget-conscious racer and the 750 horsepower range," says Guy Tripp owner of SoCal Diesel.
When reassembling the engine, make sure you add head studs, because with this much power, the cylinders are experiencing tremendous pressures and without sufficient clamping, the heads will lift. Helping add to that lift is the amount of fuel. At 750 horsepower, upgrading to 20- or 30-percent-over injectors is necessary. "It is important anytime you deal with aftermarket injectors but especially important with Duramax injectors to have them balanced, any time you upgrade or change the sizes," says Remakel.
Feeding the injectors a modified CP3 or twin CP3's are necessary. This teamed with a good lift pump will provide for a bullet proof setup and ensure that the truck won't fall on its face or die three-quarters of the way down the track. "That's never a good feeling and one I have experienced too many times," laughs Jones.
More fuel means that more air is necessary. A well-designed 2.6 aftermarket turbocharger can get you to 750 horsepower, but at that level, driveability does suffer with a single turbo. Adding a stout twin setup will yield a better all-around driver.