The idea was to recreate the L89 427 with all aftermarket parts just to see if we could best the GM power numbers. What we didn't know until we chucked the motor on a dyno is we built a little 427 that is knocking on the door of the race-only L88. Not only did we build a pretty healthy engine, we did it without pushing everything to the limits. If we want to expand our pump-gas 427-or we should say our 0.030-over 427 (433ci)-it can be built up into the 600ci range because we used an aftermarket block. Funny how we are calling a 427 small-man, how things have changed. Last month, we covered how to blueprint an engine using this engine as the guinea pig. This story will cover the parts recipe and dyno tuning of the rev-happy Rat. Instead of trying to find a clean block out of the junkyard or swap meet, we decided to start with something better. Dart's Big M iron block will be the foundation for the build. Inside the block, we used an Eagle forged 4340 chromoly-steel crankshaft, Eagle I-beam rods, and forged JE 30cc domed pistons. To make sure this 427 sounded as nasty as possible, we ordered up a Big Mutha' Thumpr cam from Comp. Let us tell you, this cam does thump. Again, instead of trying to find a factory set of painfully expensive, rare aluminum heads, we grabbed a set of Darts new 275cc Pro 1 oval port castings. These heads have many cool features that make them better than factory, but we will get into that later. To cap off the top end, we picked up a Weiand Stealth dual-plane intake manifold and a Holley 750 CFM Street HP carburetor. Providing spark is a digital E-Curve distributor from MSD. It's a billet aluminum small body distributor that has a digital module inside so you can set the timing curve with two rotary dials. Now that you have an idea of the components we used to build our version of the L89, let's get into the good stuff. Jeff Strech from Speed-O-Motive took time out of his busy schedule to finish assembling our long block and tune it on the dyno. We used a Dart Big M block because it is cast out of Class-32 high nickel iron, has four-bolt ductile iron main caps and a bore range of 4.250 to 4.625 inches. As we stated last month, the coolest feature of the block, in our eyes, is the redesigned oiling system. Instead of oiling the cam first like the stock blocks, Dart reconfigured all the oil passages and sends it to the crank first, then up to the top end. This keeps the most critical part of the engine-the mains and rods, supplied with oil. We used a Dart Big M block because it is cast out of Class-32 high nickel iron, has four-b The rotating assembly consists of a crank and rod set from Eagle and JE pistons. The crank from Eagle is a forged 4340 chromoly-steel piece that has been finished with the company's ESP Armor process. There is a full write up on the ESP Armor process on Eagle's website if you want all the details, but the simplest way to describe it is the crank comes out with a mirror finish on all the bearing surfaces. Hooked to the 3.760 stroke crank is a set of Eagle I-beam rods that also feature the ESP Armor process. The rotating assembly consists of a crank and rod set from Eagle and JE pistons. The crank At the end of each rod sits a forged JE 30cc domed 4.280 piston, which gave us a static compression ratio of 10.25:1. At the end of each rod sits a forged JE 30cc domed 4.280 piston, which gave us a static co We looked to Moroso for the oil pump and pan. The billet spur gear oil pump from Moroso is a standard volume pump whittled out of 061-T6 billet aluminum. It has a larger mounting boss area to prevent breaking and it weights 1-pound less than a stock oil pump with pick-up. It's made to fit right under... We looked to Moroso for the oil pump and pan. The billet spur gear oil pump from Moroso is ...the 6-quart Moroso pan. The pan features a baffled area with a swinging trap door that will keep the oil contained in the pick-up area to prevent oil starvation under hard acceleration. What's even better is this thing is designed to work with a stock Chevelle chassis. ...the 6-quart Moroso pan. The pan features a baffled area with a swinging trap door that Dart designed the new 275cc oval port Pro 1 aluminum heads using wet flow technology instead of just air to closer represent the air-fuel mixture the ports have to carry. The heads are cast from virgin 355-T61 aerospace alloy and have a compact heart-shaped 119cc combustion chamber, raised exhaust ports (0.300), raised spark plug location to produce great flow for low- and mid-range power. Max flow is (per Dart's flow sheet) 352 CFM intake and 258 CFM exhaust at 0.700 inches of lift at 28 inches of water. Plus, the Pro 1s can be used with off-the-shelf pistons, valvetrain components and intake manifolds. Here's Jeff finding TDC so we can set up our new timing pointer later on. Dart designed the new 275cc oval port Pro 1 aluminum heads using wet flow technology inste We wanted this engine to sound as good as it runs so we decided to try out the Big Mutha' Thumpr (BMT) from Comp. The BMT has early exhaust valve opening, long exhaust duration and a generous amount of intake and exhaust overlap to maximize the rough idle while still being streetable. The cam specs are (intake/exhaust) 0.522/0.507 lift, 295/312 duration, 243/257 duration at 0.050, and a 107 lobe separation angle. We wanted this engine to sound as good as it runs so we decided to try out the Big Mutha' We also nabbed a set of Comp Cams' new Ultra Pro Magnum 1.7 ratio roller rocker arms. These chromoly rockers are stout pieces that feature oversized trunions, precision-sorted needle bearings and hardened roller tips, yet they're still small enough to provide good retainer and valve spring clearances. We also nabbed a set of Comp Cams' new Ultra Pro Magnum 1.7 ratio roller rocker arms. Thes The manifold is a high-rise/dual-plane design that has an operating range of idle to 6,500 RPM. The dual-plane design will provide us with a broader torque curve, but will cut down on the peak horsepower just a bit. It has a 4150-style square bore mounting flange and will clear HEI-style distributors. The manifold is a high-rise/dual-plane design that has an operating range of idle to 6,500 To keep things looking old, we had Ansen Enterprises send us a set of these die-cast aluminum valve covers. These look just like the Yenko valve covers, but we had Ansen laser etch the Dart logo in the window so there will be no mistaking what's lurking under the covers. The covers are just tall enough to clear the rockers, but had they not Ansen does make a 1-inch spacer. To keep things looking old, we had Ansen Enterprises send us a set of these die-cast alumi Since the carb and intake work hand in hand, we topped the intake with a Holley 750 cfm Street HP four-barrel manual secondary carburetor. The Street HP uses the best features from Holley's race-bred 4150 HP carbs, like adjustable air bleeds a contoured main body and no choke, but has vacuum ports and a more tame fuel curve. Since the carb and intake work hand in hand, we topped the intake with a Holley 750 cfm St To provide spark, we procured a Digital E-Curve distributor from MSD. It's a billet aluminum small body unit that has a digital module inside so you can set the timing curve with two rotary dials. There are nearly 100 different advance curves available including a vacuum advance. There is also an adjustable rev limiter under the cap so there will be no need for an external box, but one can be used if you have other things tied to the ignition like a boost controller. Jeff referred to the instructions to find the proper position of the switches to give him a total of 32 degrees when added to the 20 initial timing he will be starting with. The engine will need more initial timing put into it because of the big overlap in the cam. To provide spark, we procured a Digital E-Curve distributor from MSD. It's a billet alumin Instead of going with a big old stock harmonic damper, we decided to go with something better in the way of ATI's Super Damper. Not only will it eliminate torsional crankshaft vibrations, its also exceeds SFI 18.1 specs. It still looks nice thanks, to the black zinc chromate finished and laser-engraved 360-degree timing marks, plus it's rebuildable so we won't need to buy another one in the future. To keep perfect track of our timing, we also ordered an adjustable timing pointer. It is machined from billet aluminum and provides up to 4 degrees of adjustment. Jeff matches the pointer to the one he set up earlier for a true timing reading. Instead of going with a big old stock harmonic damper, we decided to go with something bet With everything in place, it was time to fill the engine with Shell Rotella 40W oil and prime it. After the oil pressure came up, Jeff dropped in the distributor and installed the NGK R5671A-9 plugs that were gapped to 0.032. With everything in place, it was time to fill the engine with Shell Rotella 40W oil and pr After a few more checks, the engine was ready to fire up. Jeff set the timing and then let the engine run, varying the RPM from 1,500-2,500 until it came up to operating temperature. Since this engine has a roller cam and valvetrain, the break in procedure is a little less intense compared to that of a flat tappet cam. After the engine came up to temp, he shut if off and made another round of checks, looking for leaks and so on. We were good, so after the engine cooled down he fired it back up, brought it up to 2,000 RPM and then added load with the dyno. This will up the cylinder pressure and use it to force the rings against the cylinder walls helping to seat them. Then it was time for the first pull, which Jeff stopped at 4,000 RPM just to see how the engine liked the timing and jets. With factory-installed 75 primary and 80 secondary jets in the Holley, and 32 degrees of total timing the engine laid down 339 HP and 446 lb-ft of torque at 4,000 rpm. We decided to take the next pull to 5,500 RPM. After a few more checks, the engine was ready to fire up. Jeff set the timing and then let Our air fuel ratio was about 14.1 under full throttle, which was a bit lean for our tastes. We would like it to be more in the 11.8-12.2 range, so we upped the jets to a set of 82 in the primaries and 87 in the secondaries. Jeff took this pull to 5,500 RPM and this time we started to see some real power: 481 HP at 5,500 and 468 lb-ft at 4,100. Our air fuel ratio was about 14.1 under full throttle, which was a bit lean for our tastes Our air fuel ratio was a bit rich on that last pull so we swapped in a set of 79 primary and 83 secondary jets. Again, the engine didn't look like it was dropping off yet so Jeff took the pull up to 6,000 RPM and we got 515 HP at 6,000 and 474 lb-ft at 4,100, but our exhaust gas temperatures (EGTs) were a little high. While this ended up being the highest hp pull of the day, the engine was on the verge of detonation so we decided to bring it down a little so it will live a nice long, happy life on pump gas. Our air fuel ratio was a bit rich on that last pull so we swapped in a set of 79 primary a We pulled out 2 degrees of initial timing and dropped the jets to 80 primary and 84 secondaries. The Rat put down 507 HP at 6,000 RPM and 471 lb-ft at 4,100 rpm with good air fuel ratio and lower EGT's. That is nothing to sneeze at, especially for a street car engine. Also, if you look at the torque you can see we had 453 lb-ft at 3,500 and it didn't dip below that until 5,900 RPM so this thing has a nice flat torque curve that should make a heavy car like a Chevelle pull like a freight train. We pulled out 2 degrees of initial timing and dropped the jets to 80 primary and 84 second 1 | 2 | » | View Full Article By Calin Head Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!