Whether it's reworking the ignition curve on a 400ci Ram Air III or cutting down the EGR tube on an LS1 displacing 346 ci, Pontiac owners love to tweak their machines to extract additional power. In Part I of our LS1 bolt-on bonanza, a group of engine and induction modifications for the '98-'02 LS1-equipped Firebirds were introduced.
For the LS1 faithful, the "free mods" were created when innovative owners started pulling parts and experimenting to see if the changes would net power gains. Since the LS1 responded so well to minor bolt-ons, the quest for additional power was on, and in no time a set of "cost effective mods" were developed that are widely embraced by the community for their bang for the buck. For the '98-'00 LS1, the swap to an LS6 intake manifold is very popular and typically nets the owner around 10 rwhp on a stock vehicle. The remainder of the free and cost-effective mods can be applied in an afternoon and provide significant power increases for the money and time spent. If you have a free-flowing exhaust, a hotter cam, and/or port work done to the heads, even more power can be produced.
Kadin Betts of Carrollton, Texas, owns and drives daily the 57,000-mile '99 T/A that was upgraded for this story. Real Perform-ance Motorsports (RPM) in Lewisville, Texas, performed the installation and testing of the modifications.
In the first installment, the stock LS1 intake manifold was removed, and the SLP Performance-sourced LS6 intake manifold was prepared for installation by transferring-among other items-the MAP sensor, fuel rails, EVAP canister, lines, and PCV valve. Since the owner wanted to retain full EGR functionality, he purchased a used SLP manifold and placed a call to SLP for a set of new EGR O-ring gaskets. To purchase a new SLP manifold with EGR function-ality, ask for PN 30041 that retails for $499.95. The manifold includes a predrilled hole and EGR tube. Alternately, the manifold can be purchased from SLP without the EGR provisions for $399.95 under PN 30039. Both manifolds come complete with the required pipe assembly, covers, and seals.
Completion of the LS6 intake manifold installation on a '99 Trans Am follows, as does an aftermarket lid and ported throttle body install. And, of course, most of the free and cost-effective modifications will be performed. The airbox mod, however, will not since this Bird is subjected to the ele-ments each day. Subsequent dyno testing will verify the results of our efforts by comparing baseline pulls with those done after the mods. We're shooting for 20 rwhp. Will we make it?
Recommended Parts and Supplies
- SLP LS6 manifold (with EGR provisions), PN 30041, $499.95
- SLP LS6 manifold (without EGR provisions), PN 30039, $399.95
- GM manifold gaskets, PN 12533587, $76.30
- GM LS6 intake manifold, PN 12561269, $851.46
- GM front pipe assembly, PN 12581213, $39.00
- GM throttle-body gasket, PN 12552542, $12.06
- GM covers - Qty 4, PN 12570678, $5 each
- GM seals, PN 12551933, $6.28 each
- Shaner S2 throttle-body, exchange, $119.95 satin finish, $139.95 polished
- Motorsports Technology Inc, carbon-fiber-look airlid, $129, K&N filter $49
Cost-Effective Mods
- Aftermarket Air Filter - Factory-style paper air filter replaced with a drop-in filter utilizing a cotton gauze or foam element to increase airflow, $25-$50
- Aftermarket Airbox Lid - Lid replaces factory upper airbox assembly to increase airflow, $75-$150
- LS6 intake manifold (with or without EGR provisions) - LS6 intake manifold to increase airflow, used or new parts, $300-$500
 Swapping in an SLP LS6 manifold,...  Swapping in an SLP LS6 manifold, an S2 Performance (S2) throttle body, and a Motorsports Technologies Inc. (MTI) lid netted this '99 T/A a substantial power increase. |
 LS6 Intake Install (Continued...  LS6 Intake Install (Continued from Part I)The downside of the flat LS6 intake manifold underside is that the LS1-style front and rear bypass tubes can't be reused, as insufficient space exists for the tubes to connect under the manifold. GM's solution for the LS6 was to develop a new front bypass tube and rear block-off plates. After scraping the cylinder-head sealing surfaces with a razor blade and using a grease and wax remover to prepare the mount to the manifold, the center valley tray is wiped down and the new front bypass tube and rear block-off plates are installed with a 10mm socket. Also note that the two black rubber plugs in the valley tray cover the front and rear engine knock-sensors. |
 The EGR tube has to be modified...  The EGR tube has to be modified to fit into the SLP EGR fitting. A hacksaw or cut-off wheel is used to cut the EGR tube as close to the underside of the factory flange as possible so it will no longer hang in the intake tract. Then the flange is removed, and the tube is deburred with some fine sandpaper so that the SLP nut and pipe-fitting collar can be slipped over. Had this not been an LS6 manifold, the same procedure would apply to an LS1 tube, except you don't cut the tube at the flange but rather about 11/42 inch below it, as the factory EGR tube flange will be retained. |
 After one final check, the...  After one final check, the back four intake manifold bolts are slipped into the manifold and retained with rubber bands. The manifold is then carefully lifted into the engine compartment and pushed far enough back so that the MAP sensor, brake booster hose, and vacuum lines can be attached. Next, the manifold is pushed into position, and the intake bolts are hand started. Once positively located, the 8mm intake bolts are snugged down with a 11/44-inch air ratchet before being torqued to 44 in-lb on the first pass, and then to the final torque specification of 89 in-lb. The bolts are torqued using a specific tightening sequence that starts on the center bolt of the passenger side and then goes in an alternating bank pattern from left to right and from the center out. |