Founded in 1980 by Mike Mavrigian alongside Birchwood Racing, an outfit that focused on 12 and 24-hour sports car endurance racing, Birchwood Automotive operates on a three acre facility in Creston, Ohio, a small town roughly 30 miles west of Akron. Since 1992, the company has offered custom-build engine and vehicle services as well as technical writing and photography for corporate clients including Porsche, Chrysler, Toyota, Holley Performance Products and others.
“The majority of our custom engines are primarily built for publication use by various magazines and books,” Mavrigian told us. “But more recently we’ve started to offer our services to the public for custom engine builds, vintage restorations and the occasional street rod.”
Their latest effort sees the team applying their talents to a 440-cube LS Next build, a project which is detailed in depth over at Summit Racing’s OnAllCylinders blog. “Quite simply, the Dart LS Next block design attracted me,” added Mavrigian.
”While based on the GM LS format, the Dart block features a number of performance and durability enhancements, including a priority main oiling system, high-nickel iron casting, thicker (.675-in.) decks, siamesed bores with a wall thickness of .275-in. (when cylinders are bored to 4.185-in.), elimination of the Y-block design to improve windage and bay-to-bay breathing, and more. The block provides an excellent working base for increases in bore and stroke.”
Offered from Dart in either cast or billet aluminum and a choice of 4.000 or 4.125-in. bores, Dart’s high-precision CNC machining of the raw block allows for a relatively easy build, with no need to correct any geometry or dimensional issues.
Some of the highlights of the bottom end of the build consist of a balanced Scat forged crankshaft, JE Pistons which measure approximately 2.030 inches wide on the thrust side and 1.460 inches on the non-thrust side, 4340 forged steel Scat H-beam connecting rods, and a COMP Cams hydraulic roller camshaft with lift specs of 0.624-inch with 1.7:1 ratio rockers and an advertised duration of 292-degree intake/300-degree exhaust.
Birchwood chose a set of LS3-style Trick Flow GenX 255 cylinder heads for this build, which feature CNC ported 255cc intake and 87cc exhaust runners, 69cc CNC combustion chambers, and 1.300-inch, 448-pound dual valvesprings good to .850-inch valve lift, along with an ARP cylinder head stud kit specific to the 23-bolt LS Next application.
“When test fitting the Trick Flow heads, we discovered the four outboard bolt holes on the heads were 0.350-inch in diameter, likely to accommodate OE- size 8mm bolts on a GM factory LSX block,” said Mavrigian. “To use the required 3/8-16 ARP studs for the Dart block, we enlarged and chamfered these four holes on each head to 0.390-inch, more than enough for the 3/8-inch studs that the Dart block requires.”
On the top end of the build, Birchwood selected an MSD 6LS-2 controller and MSD coils to handle ignition duties, while NGK V-Power plugs gapped to 0.045 inch provide the spark.
The team ran into a clearance issue with the Harland Sharp roller rockers they’d selected for the build, as they hit the undersides of the stock-height valve covers. “Rather than going to taller valve covers, we installed a pair of ¾-inch tall ICT billet aluminum spacers to get the necessary clearance,” Mavrigian explained.
The team tapped Holley Performance for the single plane intake manifold and 850 cfm double pumper carburetor, along with a set of the company’s new cast aluminum valve covers that feature bosses to mount a set of coils without the need for unsightly coil brackets.
Once assembly was completed, the team headed over to Gressman Powersports in Fremont, OH to put the new mill on the dyno. “Scott Gressman plotted a custom ignition curve using the software supplied with the MSD ignition box,” Mavrigian added. “Timing at idle was set at 15 degrees, which ramped up to 27 degrees by 2,500 rpm.”
They noticed that as the motor was reaching peak power levels, the SuperFlow dyno’s air/fuel monitor indicated a lean condition, which was remedied by swapping out the #80 jets in the primaries and secondaries for #88s.
“Given more dyno time, we could have made some incremental power increases by messing with the carburetor and ignition timing,” admitted Mavrigian. “But all in all, our LS Next will make a nice stump puller in a mid-size muscle car or an F-body.”
Of that we have no doubt. Check out Birchwood Automotive’s website to see all the services offered by this world-class performance shop and see what they can do for your next project!