The 15's were one year only ('70) 455 heads with 87cc chambers and small valves/press-in studs. Perfect chamber size for streetable comp ratio on a 400 - just change the valves and studs and you'll be in good shape. Save the 6X's for a 455 build unless you plan to add some boost power-adders or want to go with 87 octane on your 400.
__________________
1967 GTO
Tyrol Blue/Blk Cordova
400, TKO-600, 8.2 Posi w/3.55
400 + .020, decked to .005
SD Performance 240+CFM 670 heads
RARE HO/RA manifolds
RARE 2.5" Exhaust (18" Magnaflows)
SD "Stump Puller" HR cam (230/236, 112LSA, 107.5 ICL)
PRW stainless 1.52 roller rockers
Forged TRW slugs
SCAT H-Beam forged rods
|