Back in the February '11 issue, we upgraded a GM Performance Parts 330hp crate motor with a Brodix Top End Kit and valvetrain stuff from Lunati. When we got all the parts installed and ran the engine on the dyno, the results were lackluster to say the least. We only added 27 hp and 11 lb-ft to the crate motor's baseline. Those numbers were not enough to justify the money or work that was invested. We realized our cam choice was not right to support the parts we had, so we picked up a different cam and stuffed it in. Speed-O-Motive was our first dyno place, but we relocated to Vrbancic Bros. Racing, which is much closer to our shop. Both places use the same DTS model dyno with the same correction parameters, so the differences between the two facilities were minimal. As a footnote, the Vrbancic brothers also own The Carb Shop, which happens to be right next door to the dyno, but they only have one website, which is directed to The Carb Shop. The new cam (after a bit of tuning from Bob and George Vrbancic) produced more respectable numbers, and here is how it all went down. We'll give you a small refresher on the previous story, but you should go to www.superchevy.com and check out the entire article. Stock GMPP Crate Motor RPMHPTQ 3500239359 3600252367 3700261371 3800269372 3900276372 4000284373 4100290372 4200295368 4300299366 4400305364 4500311363 4600316361 4700319357 4800323353 4900326349 5000331347 5100330340 5200335338 5300332329 5400332324 5500331316 Top-End Swap V1 RPMHPTQ 3500248373 3600261381 3700268381 3800278384 3900284383 4000291383 4100294377 4200300375 4300301368 4400306365 4500310362 4600317362 4700324363 4800330361 4900338362 5000343360 5100346356 5200349352 5300350347 5400352342 5500356340 5600355333 5700359331 5800359325 5900359320 6000362316 1 We started with a GMPP 350ci crate motor to which we added a Holley Ultra double pumper carburetor and MSD GM HEI billet distributor and wires. The engine put out 335 hp at 5,200 and 373 lb-ft at 4,000—not too bad for an iron-head, 9.1:1-compression motor. 1 We started with a GMPP 350ci crate motor to which we added a Holley Ultra double pumper 2 We then tore the top end off along with the valvetrain and installed the Brodix and Lunati components. The Brodix top-end combo comes with a set of 180cc runner aluminum heads (2.020 intake, 1.600 exhaust valves, 64cc combustion chambers, though ours were ordered with optional 60cc chambers), Horsepower 1 dual-plane intake manifold (operating range of idle to 6,000 rpm), tall cast-aluminum valve covers (breather holes will need to be added), head bolts, washers, intake bolts, valve cover hardware, head gaskets, intake gaskets, exhaust gaskets, carburetor gaskets, valve cover gaskets, and NGK spark plugs. We coupled the top-end kit with a Lunati Voodoo cam with lift of 0.555 int./0.566 exh., advertised duration of 261 int./267 exh., duration @ 0.050 of 231 int./237 exh., with a 106-degree lobe center and a set of 1.5-ratio Voodoo aluminum roller rockers. This combo only added 27 hp and 11 lb-ft of torque, so you can see why we needed to rethink our recipe. 2 We then tore the top end off along with the valvetrain and installed the Brodix and Lun 3 We looked for the cam to bring up the numbers and decided to go bigger. We picked up another Lunati Voodoo cam, but this one has lift of 0.578 int./0.585 exh., advertised duration of 273 int./279 exh., duration @ 0.050 of 243 int./249 exh., with a 110-degree lobe center. The larger lift and longer duration of the cam allowed the heads to pull more air into the cylinders and in turn make more power. 3 We looked for the cam to bring up the numbers and decided to go bigger. We picked up an Top-End Swap V2.0, No Spacer RPMHPTQ 3500271406 3600280409 3700287407 3800294406 3900299403 4000304400 4100311398 4200317397 4300325397 4400333398 4500342400 4600350399 4700358400 4800364398 4900367394 5000371389 5100373384 5200376380 5300380377 5400385375 5500391373 5600394370 5700399368 5800404366 5900406362 6000410359 Top-End Swap V2.2, 1-inch Open Spacer RPMHPTQ 3500266400 3600275402 3700281398 3800286395 3900292393 4000300394 4100310398 4200321402 4300331405 4400342408 4500352411 4600360411 4700365408 4800369404 4900375402 5000380399 5100383395 5200387391 5300391387 5400397386 5500401383 5600405379 5700407375 5800409371 5900411366 6000412360 6100412355 6200416353 Top-End Swap V2.2, 1.5-inch Spacer RPMHPTQ 3500269404 3600278405 3700285404 3800291402 3900296399 4000302397 4100309396 4200318398 4300328400 4400339404 4500349408 4600359410 4700367410 4800373408 4900378405 5000382401 5100386397 5200390394 5300395391 5400401390 5500405387 5600409383 5700412379 5800415376 5900417371 6000419366 6100402362 6200420356 4 Bob knew there was a bit more potential in the engine and suggested we add a spacer to increase plenum volume to the intake. The 1-inch open spacer added 2 lb-ft of torque at the peak of the previous test but moved the new torque peak down to 4,500 rpm. Compared to the earlier 4,500-rpm peak, the gain was 11 lb-ft. The same can be said about hp at the old peak. We saw a 2hp gain, but our new peak was at 6,200 with 416 hp. 4 Bob knew there was a bit more potential in the engine and suggested we add a spacer to 5 Just to see if bigger is better, we tried a second spacer, this time a 1.5-inch-thick, four-hole design from Wilson Manifolds. This spacer did improve our peak horsepower numbers, upping them to 420 hp. We did see a 1 lb-ft drop in torque, but we think 1 lb-ft is worth 4 hp. The new cam choice and 1.5-inch spacer now made our gains 85 hp and 37 lb-ft over the stock crate motor. 5 Just to see if bigger is better, we tried a second spacer, this time a 1.5-inch-thick, SOURCES Brodix 301 Maple P.O. Box 1347 Mena AR 71953 479-394-1075 www.brodix.com Vrbancic Brothers Racing 909-930-9980 www.customcarbs.com Holley 1801 Russellville Road Bowling Green KY 42101 270-781-9741 www.holley.com MSD 915-857-3344 www.MSDIgnition.com Lunati 11126 Willow Ridge Drive Olive Branch MS 38654 662-892-1500 www.lunatipower.com By Calin Head Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!