Big Bang Nitrous: Lean Is Mean

Lean Is Mean

Hot Rod - - Contents - Richard Hold­ener

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

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