Big Bang Nitrous: Lean Is Mean
Lean Is Mean
hThere is nothing like a big nitrous backfire to destroy a perfectly good engine. This happened after the internet nitrous guys insisted we subject an LS engine to the same treatment given our Big Bang turbo combinations where we added a good set of heads, cam and intake, and a pair of turbos to a high-mileage 4.8L, then cranked up the boost to the breaking point. After seeing showoff numbers like 1,482 hp, the nitrous guys wanted in on the action.
To find the answer to the nitrous question, we secured a highmileage 5.3L LM7 from a local LKQ Pick-A-Part, increased the ring gap on the factory (high-mileage) rings, and put it back together. All the other components remained stock, including the block, crank, rods, pistons, bearings, oil pump, pan, pick-up, and lifters.
We replaced the stock LM7 cam with a Stage 4 LS3 cam from Brian Tooley Racing. Though designed for a healthy rec-port (LS3) application, the Stage 4 cam (0.618/0.596 lift, 233/250 duration, 113+3 LSA) has proved very effective on cathedral-port, nitrous applications. The cam was teamed with a set of Fast-As-Cast, GenX 220 heads from Trick Flow Specialties. The GenX 220 heads feature one of the biggest ports we could fit on our small-bore nitrous application. Topping the TFS heads was a Holley Hi-Ram induction system with a lid designed to accept a pair of 4150 throttle-bodies (or carburetors).
01] Why is the upper part of the Hi-Ram intake sitting in a trash can, you ask?02] The Big Bang nitrous engine started out life as a 5.3L LM7. The Gen 3.5 featured factory press-fit Gen IV pins.03] The only change we applied to the stock bottom end was to remove the pistons and increase the gap on the factory rings.04] This tool from Total Seal made gapping the stock rings a snap.01020304