Aluminum Big Block Chevy on Nitrous

I've been working on a nitrous story for about six months now, while learning as much as i can about the subject. This is the second time i've rebuilt The Big Block From Hell, which appeared in the May 2007 issue of ST, and which also can be found in the tech article archive here on the site.

The first rebuild was prompted by the fact that the engine had a ton of blow-by, thanks to a piston ring package that was a tad too loose for the street. The engine made great power, but it would fill the puke tank up after a few hours of run time. The second thing was that although the engine would run on pump gas, it showed signs of detonation whenever it was fed the sub-par 91 octane crap fuel we have in California. It probably would've lasted a long while on the 93 octane that's available in most other states. So i said, "Screw it, lets give it more compression and a big hit of nitrous and see what it'll make."

This would require race fuel, but 7 dollar a gallon fuel is cheaper than a new engine. If we kept running the engine on 91 octane it was going to hammer the rod bearings until they spun and that would have been catostrophic. So i rebuilt the engine with new pistons designed for N20, a stout ring package that would eliminate much of the blow-by, and added a fogger system.

The first trip to the dyno was educational. With the help of Nitrous Supply's Mike Thermos, we jetted the fogger system for what we figured would be a 175 horsepower shot, taking 10 degrees of timing away from the ignition when the bottle was on. The problem was the engine was very efficient, and that 175 shot turned out to be almost a 250 shot once the motor got done with it. We didn't take enough timing away and the engine detonated just slightly, which was enough to beat up the rod bearings again. So i tore the engine down, bought new bearings, and spent last weekend putting the short block back together. We'll go back to the dyno for another shot at making 1300-plus horsepower again next month.