|CAM SPECS |
| ||INTAKE ||EXHAUST |
|LOBE LIFT ||.516 ||.498 |
|DURATION @ .05 ||277 ||285 |
|LOBE SEPARATION ||116.0 ||116.0 |
|GROSS VALVE LIFT ||.877 ||.846 |
1. During the rebuild, we...
1. During the rebuild, we replaced the old LSM camshaft with a new grind from Comp Cams. The new cam offers .0010-inch more lobe lift on the intake side and nearly identical exhaust lobe lift. This cam also offers a few more degrees of duration on the intake side as well. While it's not a nitrous-specific grind, it did perform well during our dyno testing.
2. We installed the cam "straight...
2. We installed the cam "straight up" with zero degrees of advance per Comp's instructions using Moroso's large degree wheel, which we bought from Summit Racing, and Proform Parts magnetic base dial indicator stand. During our dyno testing, we advanced and retarded the cam using the adjustable Jesel belt drive timing system, and found no additional peak power.
3. Our ProFiler 12-degree...
3. Our ProFiler 12-degree Hitman cylinder heads remain unchanged except for gaining a new set of replacement LSM valvesprings. We sealed the heads to the block using Cometic .040-inch multilayer steel gaskets. The MLS gaskets are well-suited to high cylinder pressures this engine will generate on the bottle, and we've never had an issue with these gaskets maintaining a good seal. We also opted once again for Cometic's intake manifold gaskets because they required only minimal trimming to align with our ported intake manifold.
Part Three: The Nitrous System
1. The next major change to...
1. The next major change to our engine was the addition of a direct port nitrous oxide system from Nitrous Supply. There are several ways to add nitrous to a big-block Chevy, with plate systems being one of the easiest to install and most popular. We went the direct port route though because our intake manifold has a few distribution issues, which result in the corner cylinders running leaner than the middle ones. In naturally aspirated form, this isn't a huge deal and the engine runs fine, albeit on the brink of detonation. We didn't want to take any chances of hurting the engine on the bottle, so we went with the cylinder-to-cylinder tunability of the direct-port wet nitrous system.
2a. The only drawbacks of...
2a. The only drawbacks of this system are its complexity and that the intake manifold must be removed from the engine so that the runners can be drilled and tapped for the nozzles. The positive aspects far outweigh the negatives though. Each nozzle has a passage for nitrous and fuel to be injected into the runner via individual jets. Because each runner has a separate supply of fuel and nitrous, each cylinder's air/fuel ratio can be tailored. If the cylinder is running lean, we can add fuel or take away nitrous with a jet change to get it running properly.
3. The crew at Nitrous Supply...
3. The crew at Nitrous Supply drilled our manifold for the system, bent up the stainless steel hardlines from the solenoid valves to the nozzles, and plumbed the system. We then sent the system and our manifold to Induction Solutions to have the system flow-tested and blueprinted. The benefit of doing so was that IS's owner, Jeff Johnson, was able to see what we had for fuel lines and fittings and after flowing the system, he gave us a list of what size nitrous and fuel jets to install so that we didn't waste a lot of time on the dyno trying to dial-in the system. As you can see in the photo, -3 hard lines run from the solenoid directly to the nozzles and interchangeable jets.
4. The fuel side of our new...
4. The fuel side of our new nitrous system needs to be regulated and so we made a custom mount and added an Aeromotive adjustable fuel pressure regulator. This regulator allows us to set the pressure on the nitrous independently of the engine's fuel system.
5. To supply nitrous oxide...
5. To supply nitrous oxide to the system, we chose a 10-pound aluminum bottle with super high flow valve from Nitrous Oxide Systems, which is connected to the solenoids via a -6 stainless steel-braided line and a Y-fitting.
Part Four: The Ignition
The last piece of the puzzle is a high-tech ignition system that we bought from Summit Racing designed specifically for using N2O. The MSD 7531 programmable Digital 7 ignition system features MSD's world-famous capacitive discharge ignition, but that's not the cool part. The cool part is that this ignition will automatically retard the ignition timing of the engine whenever the nitrous button is activated. It will also ramp the extra timing back into the engine at a programmable rate after the button is released. This allows any extra nitrous to be spent from the cylinders before the timing is back to full advance. You bracket racers out there will love that you can also program this ignition system to turn the nitrous on and off at a specific time or rpm for repeatable runs. Combine those features with the 7531's data-logging capability, and you've got a box that will do it all for years to come.
The Final Word
We've rebuilt the Big Block From Hell to be a bulletproof nitrous-swilling monster. The tips and tricks we learned along the way will help you build or rebuild your own engine into a stout nitrous machine. Next month, we'll take a look at the various methods for tuning your engine to get the most out of it and to make it last.