When I had my stock 340 in there 600 Holley some under steering linkage headers, 2 1/4 exhaust, stock 1 5/8 inner diameter chrome tips, 323s, street radials, some crap mufflers, it usually ran 14.2 to 14.0. One time at Cecil Co track it went 13.90, it hooked, all the stars aligned, tail wind ect. But was always 14.0 or so every other time.