383 LS1 Stroker Epilogue - My First Stroker: Epilogue

Two Years In The Making, Gmhtp Proudly Presents Final Testing Of Our Garage-Built 383

Chris Werner Apr 1, 2009 0 Comment(s)
0904gmhtp_01_z Pontiac_trans_am 383_powered_trans_am_ws_6 2/17

Ah, unfinished business. It usually goes something like this: the finish line well within reach, intervening needs jump in the way, and tackling them inevitably holds up the works longer than anticipated. Such is the case here, so our apologies are in order for those who may have been holding their collective breaths during this time.

The original "My First Stroker" series, the last installment of which was printed back in the January 2007 issue, was a success with GMHTP readers looking for in-depth coverage and analysis of a homegrown LS1 engine buildup. (It even got your author some great exposure and helped land me a sweet LS book deal, but that's another tale.) A stock LS1 block was honed 0.005-over and stuffed with a forged Lunati rotating assembly featuring a 4-inch stroke crank. A Lunati Voodoo cam spec'ing out at 232/238 duration at 0.050 and 0.599/0.601 lift was utilized to actuate the valves in 215cc ETP heads via a set of Jesel shaft rockers. Capping it off was a FAST 90mm intake manifold drilled to accept a 300-hp-capable ZEX direct port system. We left the story series off with the caveats that we'd update readers as improved drag strip times became available for our newly 383-powered Trans Am WS-6, and after we gave this engine the shot of nitrous it was built to handle.

But factors like a stock 10-bolt rear made serious efforts at such tasks ill-advised at best. So began the saga of upgrades to the rest of the vehicle to better complement its now-potent underhood powerplant. We beefed up the suspension with a best-of-all-worlds BMR setup ("Suspension Intervention," November 2007), then added a bulletproof-and-beautiful Moser M9 rear in the April 2008 issue ("Bulletproof Backends"), the latter including a fully adjustable, crossmember-mounted torque arm system. With all of that taken care off, only a few items were left to address. Recipe for success: (1) Reactivate the ZEX direct port nitrous that's been dormant since the stock LS1 was removed; (2) while we're tinkering around in the engine bay, reconnect the car's PCV system, the lack of which currently has us on the wrong side of emissions laws (and is causing a gradual-but-unrelenting buildup of oil residue along the passenger side of an otherwise-spotless engine compartment); (3) get a dyno tune for optimized N/A and nitrous power; (4) bolt some sticky tires onto the ends of the 31-spline alloy axles; finally, (5) Hit the strip and let `er rip.

As with any thorough project, the devil's in the details, so read on to see how we went about all of this in a careful and well-thought-out way.

Nitrous Reactivation
First and foremost, let's talk about getting our stroker T/A ready for its ZEX nitrous system to come back to life. In part 4 of our series, we expressed concerns about lack of adequate fueling while on the spray. That uneasiness was quickly put to rest when renowned east coast tuner Matt Sorian, proprietor of TTP (a business that has recently relocated to a new, badass facility in Little Falls, NJ) assured us that our existing Racetronix system would be up to the task without the need for any sort of pump voltage booster or similar method of increasing flow potential. He was also adamant that he'd be able to give us a nitrous tune compatible with 93 octane fuel. No undercar wiring to do, and no having to scrounge up high-dollar, high-octane unleaded on race day? We were sold.

As far as nitrous tuning goes, we had originally mentioned looking at two options: one would be installing a product that would retard ignition timing automatically when the nitrous is engaged; the other would consist of running a "de-tuned," nitrous-friendly calibration at all times. Since no satisfactory auto-retard product has yet come to market for stock-PCM LS engines, and because running one tune at all times would result in non-optimal performance while naturally aspirated, we decided to split the difference. TTP would provide two separate tunes--one for N/A and one for spray--and we'd use a laptop and tuning suite to load the correct one into the PCM as needed. The only problem would be actually remembering to swap the nitrous tune in before heading out for a bottle-fed pass. But we could swing that... right?




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