GM Performance Parts 350ci/330HP Crate Motor Build

Finishing off the valvetrain is a set of Voodoo 1.5 ratio, 3/8-inch stud aluminum roller rockers. According to Lunati's website, these aluminum rockers are the product of extensive testing, including special deflection and high RPM simulations. They come completely assembled with poly locks.

For the carb, John looked to Holley and picked up an Ultra Double Pumper fuel sprayer. Not only does it look killer with black anodized, billet aluminum metering blocks and base plate, it has an enhanced fuel curve and 4-corner idle. Other notable details include mechanical secondaries, clear fuel level sight plugs, 1 timed (spark) port, 1 full vacuum, 1 PCV port, and an electric choke.

To light the fire, a GM-style HEI billet distributor, wires and separators were ordered from MSD. We won't need the wires until the engine goes in the car, as Speed-O-Motive already uses MSD wires on its dyno. Since John has plenty of firewall clearance, the simple coil-in-cap design of the HEI was a simple choice. Unlike a junkyard unit, the MSD HEI has a digital module and hot coil to provide plenty of spark energy.

With the carb and ignition installed on the out-of-the-box GMPP 350ci/330HP crate motor, the timing was set to 34 degrees total advance, then the engine was broken in. Once Jeff was confident everything was ready, he did an initial low rpm pull. Everything looked good, so he did a full pull and noticed the air/fuel ratio was off. After a few jet and power valve changes, he got it nailed and clicked off the results listed on the next page. As advertised, the engine laid down 335 hp and 372 lb-ft at the peaks. It was pretty much out of steam at 5,200 rpm, but still not too shabby for a low-buck crate motor.

All the stock stuff was ripped off in true pit crew fashion, and the new Brodix and Lunati components installed. Having all the correct gaskets, bolts, and so on really made this a quick swap on the dyno.

The one thing we have not mentioned so far are the pushrods. Since each motor can be different, it's hard to include a correct size pushrod with so many variables. The ones we used were supplied by Speed-O-Motive, and measure 8.050-inch on the intake side and 8.100-inch on the exhaust. Since this is now a solid roller motor, Jeff set the initial/cold valve lash to 0.010. Then he fired it up, let the engine come up to temp, and re-adjusted them to 0.016 lash while everything was hot.

...Again, after a couple of pulls to figure out the carb tuning and perfect timing, Jeff did a full pull, this time to 6,000 rpm. The new components let the engine breath better, allowing for more power at higher rpm.

The new combo netted us 362 hp and 384 lb-ft at the peaks, and another 800 rpm of usable power. Unfortunately, 27 hp and 12 lb-ft is a small gain, but we know exactly what the problem is-too small a cam. We already have a larger Lunati solid roller (lift 0.582, advertised duration of 276 int./284 ext., duration @ 0.050 of 243 int./251 exh., with a 110 lobe center) on the way for later testing, so stay tuned.