If you are looking for the best-kept secret in the performance industry, look no further than your local wrecking yard. We know, the powerplants are often caked with grease and grime and are usually a far cry from a shiny, new crate engine, but they don’t cost crate engine money either, now do they! Heck, yanking an engine from the local Pick Your Part doesn’t cost as much as a typical rebuild kit, let alone an assembled, ready-to-run small-block. Sure, a stock truck or passenger car 350 might not pump out the ponies like those fancy engines, but the savings offered by shopping at the junkyard can provide some serious cash for upgrades. We decided to test our theory by snatching up an engine from the yard to demonstrate how effective a simple cam swap can be. The idea was to pull a (hopefully) running small-block then put it through its paces on the dyno, first with the stock cam then again after a cam swap. Things didn’t go exactly as planned, but that doesn’t mean we didn’t wind up with an impressive small-block when we were done.
If your local yard is anything like ours, the best place to find a usable small-block is in the truck section. Sure, you can find pedestrian small-blocks (both 305 and 350s) in fullsize passenger cars, but you are not likely to run across anything like an aluminum-headed L98 (TPI), or even an L82, L48, or any other performance-oriented L-series small-block. We like the truck section because 350 Chevys are not only plentiful, but you will likely find four-bolt main blocks there as well. For stock power production, the hot ticket is the L31, Vortec-headed 350 offered from 1996-’02 in truck, van, and SUV applications. In addition to the impressive head flow, the L31 also featured a hydraulic roller cam and a power rating of 255 hp and 330 lb-ft of torque. The previous generation TBI engines produced just 210 hp thanks to reduced compression, a flat-tappet cam, and minimal head flow, to say nothing of the less-than-stellar induction system. When building a small-block on the cheap, it is always beneficial to start with one that makes more power.
After locating what we thought was a suitable L31 for our test, we brought it back to Westech Performance for testing, only to find out it had a major issue. After removal of the factory EFI system (which we tossed), we discovered that our L31 was missing one important component: the hydraulic roller cam. The block had the provisions for the roller lifters and spyder (hold-down) assembly and even the boltholes and machine surface for the cam retention plate, but this Vortec-headed small-block was sporting a flat tappet cam. We would later find out that it had a GM part number for an early TBI motor. Whether this was a TBI upgraded with Vortec heads and intake or an L31 downgraded with a factory flat-tappet cam actually mattered not for our test. We simply shifted gears from the installation of a hydraulic roller cam to the less expensive flat tappet grind. Problem solved.
Before running the 350 on the dyno, we had to install a few components. Since we ditched the factory injection and distributor, we needed both fuel and spark. The EFI was replaced by a simple dual-plane, Eliminator intake from Speedmaster. Designed to maximize power up to 6,500 rpm, the dual-plane, high-rise intake was perfect for both our stock and soon-to-be-modified small-block. Feeding the Speedmaster intake was a Holley 650 XP carburetor. If you are a serious yard hound, feel free to grab a Rochester Q-Jet, as they work well at this power level and will be considerably less costly than the trick Holley. Spark for our small-block came from an MSD billet distributor, but a non-computer-controlled HEI is more than adequate and can be had for peanuts at the yard (especially as part of a complete engine assembly). After adding a set of long-tube headers, an electric water pump, and five quarts of fresh oil, it was time to fire the old girl up for testing. Run with the new induction system and stock cam, the low-compression, Vortec-headed 350 produced 277 hp at 4,500 rpm and 352 lb-ft of torque at 3,600 rpm. Obviously, the stock cam was pretty mild, and did not allow the small-block to take full advantage of the airflow offered by the heads, intake, and carb, but all that was about to change.
Since our small-block had sufficient head and intake flow, what it really lacked now was cam timing. We weren’t looking to install the proverbial 3/4 race cam, just something to allow our small-block to breathe. There were (of course) limitations in our system that kept available cam timing in check. These variables included piston-to-valve clearance and retainer-to-seal clearance on the Vortec heads. After measuring the heads, we found we had a maximum of 0.500 retainer-to-seal clearance, meaning the 0.480-inch exhaust lift offered by the intended XE268H cam would just fit. After checking the clearance, the heads were treated to a valvespring upgrade. We installed a set of springs (PN 981-16) that dropped right in place on the Vortec heads and even allowed the use of the factory retainers. The additional spring pressure (from 80 to 120 pounds of seat pressure) provided the necessary rpm potential and coil-bind clearance for the XE268H cam. The Xtreme Energy cam itself offered a 0.477/0.480-inch lift split, a 224/230-degree duration split, and a 110-degree LSA and was combined with a new set of lifters (PN 812-16), also from Comp Cams.
After swapping over to the new cam, lifters, and springs, the flat-tappet, small-block was ready to run. We first treated the cam to a proper break-in procedure by exceeding 2,400 rpm for over 30 minutes to get the cam and lifters properly acquainted. Prior to installation, we applied moly-based assembly lube to both the cam lobes and bottom of the lifters. We hedged our bets even further by changing the oil to a high- ZDDP break-in oil from Comp Cams. After a successful break-in, we were free to run the engine in anger. After dialing in the timing and air/fuel mixture, the Comp-cammed small-block produced 343 hp at 5,400 rpm and 381 lb-ft of torque at 4,100 rpm. The new Xtreme Energy cam offered significant power gains past 3,500 rpm, but lost no power to the stock cam even down low. The cam swap netted an increase of 66 hp, pretty impressive from a single component—especially a relatively mild street cam. We know these heads will support well over 400 hp with more compression, a low-mileage short-block, and slightly wilder cam timing, but for now, we can say without a doubt we have successfully taken our junkyard engine to the Xtreme.
01. Even a tired, old junkyard small-block will respond to a cam swap if you select the right cam.
02. After pulling the small-block 350 from the junkyard, we replaced the factory EFI induction with this dual-plane Eliminator intake from Speedmaster.
03. Feeding the dual-plane Eliminator intake was a Holley 650 XP carburetor we had on hand. For the ultimate in low-buck, it is possible to run one of the many Q-Jet carbs available in the yard. Note also the MSD billet distributor.
04. Run on the dyno with the stock cam using the Speedmaster intake, Holley carb, and MSD distributor, the Vortec-headed small-block produced 277 hp at 4,500 rpm and 352 lb-ft of torque at 3,600 rpm. The mild cam timing was obviously tuned for low-speed torque production.
05. We wanted some serious power for our junkyard dog, so we selected a Comp XE268H cam. The hydraulic flat tappet cam featured a 0.477/0.480-inch lift split, a 224/230-degree duration split, and 110-degree LSA. Before choosing the cam, we made sure to check available retainer-to-seal clearance (an issue with Vortec heads), but we measured sufficient clearance for 0.500-inch lift.
06. The new XE268H cam was teamed with a fresh set of hydraulic flat tappet lifters (PN 812-16) from Comp Cams.
07. To ensure adequate rpm capability and coil-bind clearance, we replaced the tired factory springs with a set of springs (PN 981-16) from Comp Cams. The springs dropped right in place using the factory Vortec retainers.
08. To replace the stock cam, we used this nifty pneumatic/hydraulic damper puller.
09. Removal of the front cover provided access to the factory timing chain. Before removal, we rotated the engine to TDC to line up the dots on the cam and crank sprockets.
10. Out came the wimpy factory truck cam to make way for the more powerful Xtreme Energy grind.
11. Prior to installation of the XE268H cam, we made sure to apply moly-based assembly lube to the cam lobes and bottom of the lifters.
12. After installation of the new cam, lifters, and springs, it was necessary to adjust the valves. We settled on a half turn of preload using the factory stamped-steel (guided) rockers.
13. Before firing up the new combination, we drained the old sludge and replaced it with some 10W-30 (ZDDP-enhanced) break-in oil from Comp Cams.
14. After a lengthy break-in cycle, we were able to run the small-block once again in anger. Equipped with the new cam, lifters, and springs, the power output of our small-block jumped to 343 hp at 5,400 rpm and 381 lb-ft of torque at 4,100 rpm. The cam swap netted an additional 66 hp and did so without losing any low-speed power (a common occurrence with cam swaps).
350 Chevy Cam Swap—Stock vs. XE268H
Even sporting the Vortec heads and a good intake and carburetor, our small-block was no powerhouse. Run with the stock flat-tappet cam, the 350 truck engine produced just 277 hp at 4,500 rpm and 352 lb-ft of torque at 3,600 rpm. The stock stick must have been seriously mild to produce those numbers. After upgrading to the XE268H cam and new lifters and springs, the power output jumped to 343 hp and 381 lb-ft of torque. Substantial gain occurred past 3,500 rpm, but there was no trade-off in power lower in the rev range. Equipped with the new Comp cam, the small-block was now ready for some street action.