PROJECT LS2: Final Prep and Dyno (Part 1)

Mike Mavrigian has written thousands of technical articles over the past 30 years for a variety of automotive publications, in addition to writing nine automotive technical books for four different publishers. Mike also owns and operates Birchwood Automotive in Creston, Ohio, where he builds custom engines, street rods and performs vehicle restorations. Mike can be reached at 330-435-6347 or . Birchwood’s website is

Whenever I build an engine, regardless of my confidence in terms of fitting and assembly detail, I'm always a bit apprehensive when it comes time to light the fire. But when things go picture-perfect and you hit high numbers without a single glitch, it's a feeling that's better than sex (I'm sure you know what I mean). This LS program proved to be a total success. First, let's start with the final preparation, then we'll get to the live-fire exercise.


In order to run our water pump with a serpentine belt, I needed a belt tensioner and tensioner pulley. I've heard many complaints about the OE GM tensioner. Apparently, the belt likes to jump off of the tensioner pulley at high rpm. Luckily, COMP Cams has recently introduced a very cool CNC billet machined and adjustable LS belt tensioner, with an already-installed pulley (COMP P/N 54021). This tensioner mounts onto the right side of the water pump in the OE location. The tensioner includes two 1" long aluminum spacers that may be used if needed. For installation without the spacers, you'll need a pair of 10mm x 1.5 x 40mm bolts. For installation with the spacers, 55-60mm length is fine. Once I test-mounted the COMP Cams adjustable serpentine belt tensioner with pulley, I knew that I had screwed up early-on, since the tensioner pulley and crank pulley weren't even close to aligning. The crank pulley was about 1.5" too far forward for correct belt line-up. That's when I discovered that I had inadvertently ordered the wrong damper hub. As it turns out, our original hub was part numbered for an LS engine in a truck/SUV application (ATI P/N 916430A). A quick call to ATI remedied the situation. The correct damper hub for this application is P/N 916032 (Corvette application). The difference in length of each hub (from the hub's damper contact face to the rear end of the hub) was 1.58" (the 916430A hub is 4.350" long, whereas the 916032 hub is 2.770" long). So, if you're using a Camaro or Corvette tensioner (or an aftermarket tensioner, most of which are designed for the passenger car fitment), you'll need the shorter P/N 916032 damper hub. Our final setup required no spacers (the tensioner mounted directly to the pump body's bosses). Hey, there may be egg on my face (I never claimed to be the brightest bulb on the Christmas tree), but at least I can pass this tip along so you don't run into the same problem. This is a good example of why we build these run interference for our readers, pointing out the potential for mistakes in the process (especially if you're like me and rush to order a part without realizing that there is more than one LS pulley depth setup). Since we're not planning to add any driven accessories (we only need to run the water pump on the dyno), the proper fitting serpentine belt for our application is a 43.5" long belt (I chose a Goodyear Poly-V Gatorback, P/N 4060435). In combination with our ATI damper/pulley, our Edelbrock water pump's pulley and our COMP Cams tensioner/pulley, this length worked out perfectly, placing the adjustable tensioner at about the half-way point in its adjustment range. Again, this length was ideal for driving only our water pump for our dyno run. Naturally, once you add an alternator, power steering pump, etc., a longer belt would be needed.


Our Moroso oil pan (P/N 20141) features -10 fittings to accommodate a remote-mount oil filter. I plumbed a temporary remote filter just for dyno use, using a Perma-Cool P/N 1701 oil filter mount. This mount features 1/2" NPT port threads and a 3/4" x 16 filter thread size (to accept a Fram PH8A or HP-1 or equivalent filter). I installed a pair of -10 male to 1/2" NPT male fittings to the filter mount, and plumbed with -10 hose and -10 hose ends. All hose end tightening was done using our Fragola -10 aluminum AN wrench from our Fragola AN wrench set. Always use an aluminum AN wrench whenever servicing aluminum hose ends to prevent marring the hose ends. Note that the correct oil-flow routing is as follows-the forward -10 tube at the oil pan is the engine-OUT location, which connects to the remote filter adapter's IN port. The filter adapter's OUT port plumbs to the pan's rear-most IN tube. The pan's forward tube is ENGINE OUT and the pan's rear tube is ENGINE IN.


In order for the MSD timing controller to fire the coils, you'll need two GM AC Delco coil harnesses (P/N 12582190), which sell for about $75.49 each (one for each bank). Pay attention to the MSD wiring instructions when connecting these coil harness connectors since it's easy to flip the end-for-end (mixing cylinders 1 and 7, for instance). Each coil harness connector features four wires. Each connector uses a pink wire (12-volt), brown wire (sensor ground) and black wire (ground). The fourth color indicates connector-to-coil cylinder location.


Once the engine has been built and dyno'd, you need a way to store the motor. The LS block is unique and will not accept an engine cradle designed for earlier GM blocks. I looked around and, to date, the only source I found was Scoggin Dickey, who offers its own custom-made cradle (P/N SDCRADLERED). This cradle is a bargain, selling for a mere $37.50. It's very well made, powdercoated red and the base is drilled for caster wheels (wheels not included). The SDPC cradle features very nice fabrication quality (not a typical "bargain-basement Chinese" cradle). If you plan to build a few LS engines, either make your own or buy these. You'll need ‘em. By the way, attachment of the cradle to the block requires two 10mm x 1.5 x 25mm bolts for the forward mounts and two 10mm x 1.5 x 45-50mm bolts at the rear.


In addition to hooking up our MSD wiring harness and the two coil harnesses, I needed to allow for an oil pressure sender connection on the dyno. Since we're not running a complete OE wiring harness and had no provision for simply plugging into the OE sensor, I removed the OE oil pressure switch from the rear of the valley cover plate. After obtaining a spare 16mm straight-thread plug, the same as used on the forward left side of the block to plug an oil galley (GM P/N 11588949), I drilled the center of this plug using an 11/32" drill and tapped the hole to 1/8" NPT. This allows easy adaptation to a common NPT-thread pressure sender. Since the plug head O.D. is round, you'll either use a pair of pliers to install it or grind a couple of shallow flats on opposing sides of the plug's head for adjustable wrench use. Don't flatten the edges of the plug head too far, though, since the crush washer O.D. is very close to the plug head outer edge.


I delivered the engine to Gressman Powersports in Fremont, Ohio, on Oct. 31 (yep, Halloween day) to run our LS on their Superflow engine dyno. We added 8 qt. of 15-40 Rotella oil to the 7 qt. Moroso sump and the remote oil filter. We attached the dyno's oil pressure sender to the 1/8" NPT fitting that I previously added to the valley cover. The cooling system was filled with water via the dyno's cooling tower and the system was bled. Dyno fuel (94 octane pump gas) was plumbed to the Edelbrock 800 cfm carb. We plugged the MSD timing control module to the MSD harness. Instead of using one of the pre-programmed curve modules, Scott Gressman opted to utilize the MSD software to program the timing curve on his laptop computer. Gressman started with a mild setup at 28 degrees total timing (the control module ramped timing initially from zero to about 12 degrees, then moving to 28 degrees total). The engine fired on the first try (always a nice feeling). After allowing the engine to reach operating temperature, its first pull showed 537 horsepower at 6,330 rpm, but we hit the built-in rev limiter. Gressman reprogrammed to move the limiter, with the next pull hitting 560 horsepower, again hitting the limiter. After adjusting again, she hit 610 horsepower at 28 degrees, but again cushioned by the rev limiter. He then bumped her up to 30 degrees total and hit 618 horsepower at 30 degrees. Finally, Gressman bumped total timing to 31 degrees for the final pull, which resulted in an impressive 625.4 horsepower at 6,800 rpm and 534.6 lbs./ft. of torque at 5,200 rpm. By the way, throttle response was absolutely incredible. This vicious puppy snapped like a pitbull releasing a rubber band at any throttle-up input. I mean, this dude sounded nasty. Gressman was extremely impressed with the Edelbrock carb (easy adjustability and fantastic response), Super Victor manifold, Trick Flow heads and Crane cam combination. There's always more to be had by playing with tuning, but 625 horses impressed the buggers out of all of us. Quite honestly, we were expecting to hit around the high 500-horsepower range as our peak, and to nail 625 was just peachy. This thing's a little monster.


AC Delco (800) 652-0406, ext. 17432

ATI (800) 652-0406, ext. 17433

Crane (800) 652-0406, ext. 17434

COMP Cams (800) 652-0406, ext. 17435

Edelbrock (800) 652-0406, ext. 17436

Fragola (800) 652-0406, ext. 17437

Fram (800) 652-0406, ext. 17438

Goodyear (800) 652-0406, ext. 17439

Gressman Powersports (800) 652-0406, ext. 17440

MSD (800) 652-0406, ext. 17441

Moroso (800) 652-0406, ext. 17442

Perma-Cool (800) 652-0406, ext. 17443

Scoggin Dickey (800) 652-0406, ext. 17444

Trick Flow (800) 652-0406, ext. 17445