706 vs. 317 Mod­i­fied (NA) 5.3L

Chevy High Performance - - Best For Boost? -

Right off the bat, it is ob­vi­ous that the stock 5.3L 706 heads eas­ily out­per­formed the 6.0L 317s. This was even more im­pres­sive when you con­sider the fact that the 317 heads of­fered more flow, larger ports, and larger in­take valves. Credit the dif­fer­ence in cham­ber size for the ma­jor­ity of the gains, as the 706 heads were a full 10 cc smaller than the 317s. Tested on the nat­u­rally as­pi­rated 5.3L, the re­sult was an ex­tra 20 hp, and al­most as much torque. Equipped with the 706 heads, the 5.3L pro­duced 468 hp and 413 lb-ft of torque. Af­ter in­stal­la­tion of the

317 heads, the power num­bers dropped to 448 hp and 398 lb-ft of torque. The ques­tion now, how would they com­pare un­der boost?

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