Mopar Muscle - - Contents -

Part 2: Kick­ing some LS butt on the dyno

Let’s cut to the chase: The LA small-block rac­ing en­gine we’ve been fol­low­ing, built by Michi­gan’s Valley Per­for­mance for the Race En­gine Chal­lenge, took home the gold. Based on av­er­age horse­power per cu­bic inch, the 376-inch un­der­dog sur­prised and over­pow­ered more than a few LS builders in the event, punch­ing out 1.963 hp for each gen­uine Mopar cube and claim­ing the class win. “We were con­fi­dent we had a com­pet­i­tive com­bi­na­tion and would give the LS en­gines and other well-de­vel­oped en­gines a run for their money,” says Jack Barna, Valley Per­for­mance’s owner. “But it was still some­what of a sur­prise to see our en­gine come out on top. It had some­thing to prove and re­ally did.” As we de­tailed in the first in­stall­ment of this story, the en­gine was built for the in­line-valve class in the com­pe­ti­tion, which had a dis­place­ment range of 370 to 490 ci. The other class was for canted valve/hemi de­signs. And while those en­gines ex­pect­edly posted big peak num­bers, Valley Per­for­mance’s out­put was right with them when it came to power-per-inch. “Our num­ber was within 1 hp of the top Hemi en­gine,” says Barna. “So when it came to over­all out­put, our LA re­ally brought it home.” The en­gine posted an av­er­age horse­power rat­ing of 737 hp, which was about 4.5 per­cent lower than Valley Per­for­mance’s test pulls on a dif­fer­ent dyno. Barna at­trib­uted the dif­fer­ence to a va­ri­ety of con­trib­u­tors: a dif­fer­ent dyno, dif­fer­ent at­mo­spheric con­di­tions, a dif­fer­ent alti­tude cor­rec­tion fac­tor and more, but the bot­tom line is the en­gine squeezed out more per cube than its ri­vals. “We be­lieved a smaller en­gine would be more ef­fi­cient when it comes to mak­ing the most av­er­age power per dis­place­ment, with less fric­tion and more air­flow per cu­bic inch,” he says. “The re­sults speak for them­selves.” In our first in­stall­ment, we fo­cused on the en­gine’s block en­hance­ments and short-block as­sem­bly, out­lin­ing a num­ber of unique and cus­tom mod­i­fi­ca­tions de­signed to shore up the LA’S foun­da­tion. Valley Per­for­mance started with an early Mag­num 360 block, largely for its over­all strength and taller lifter bores.

Valley Per­for­mance started with an early Mag­num 360 block that was re­in­forced with Hard Blok in the wa­ter jack­ets and un­der­went a num­ber of mod­i­fi­ca­tions for windage-re­duc­ing oil con­trol. Valley Per­for­mance also had splayed four-bolt main caps made for it to pro­vide ex­tra sup­port for the mains. The cylin­der was bored out to 4.100 inches to un­shroud the valves.

Valley Per­for­mance en­hanced air­flow in the new heads by open­ing up the walls a bit to elim­i­nate the pushrod pinch, along with a lit­tle guide work, re­sult­ing in a strong 372 cfm at 28 inches of wa­ter. Note, too, the 5/16-inch bolt at the up­per left of the stock bolt­hole. It was to bolt up the W2-style tun­nel­ram in­take man­i­fold.

The rel­a­tively new Edel­brock Vic­tor cylin­der head is cred­ited with help­ing push this small block project to the win­ner’s cir­cle. They of­fer large, 225cc in­take ports, raised ex­haust ports and a re­vised 16-de­gree valve an­gle (stock is 18 de­grees). Out of the box, the head is good for about 345 cfm on the in­take side and 237 cfm through the ex­haust ports.

In­side the block is an Ea­gle forged crank­shaft the slightly re­duces the stroke from 3.580 inches to 3.556 inches. The rods and pis­tons in­clude Ea­gle 6.250-inch H-beam rods and cus­tom Ross forged pis­tons that con­trib­ute to an 11.66:1 com­pres­sion ra­tio. The camshaft is a Bul­let roller unit with 0.775/0.774-inch lift and 255/265 de­grees du­ra­tion.

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