Heads Up ! LT1 VS. LT4 Cylinder Head Match Up

The LT1 and LT4 cylinder head data contained was obtained by testing in our shop, and part numbers were provided by General Motors. The specifications and part numbers provided are all for original, stock parts. Cylinder heads for both LT1 and LT4 must be dedicated to the engine. For certain parts the casting and part numbers are the same.

Angle of valve seat 46 degrees both LT1 and LT4

Width of valve seat (intake) 0.030" - 0.050" both LT1 and LT4

Width of valve seat (exhaust) 0.030 ' - 0.080 ' for LT1 and 0.060 ' - 0.080" for LT4

Angle of valve face 45 degrees both LT1 and LT4

Valve spring height installed (intake and exhaust) 1.78" both LT1 and LT4

Spring pressure closed 81 - 89lb at 1.78 ' LT1 and 96 - 107lb at 1.78" LT4

Spring pressure open 246 - 265lb at 1.33 ' LT1 and 246 - 273lb at 130" LT4

Rocker arm ratio 1.5 :1 LT1 and 1.6:1 LT4

Valve lift (intake) 0.447" LT1 and 0.476" LT4

Valve lift (exhaust) 0.459" LT1 and 0.479 LT4

Valve sizes vary from year to year and are included with part numbers. Both LT1 and LT4 have54cc combustion chambers. The LT1 cylinder heads have 170cc intake runners and LT4 have 185cc intake runners. LT1 uses ball rockers and LT4 employs roller rockers.

Casting numbers for GM LT1 and LT4 cylinder heads and parts.

1992 -1993 LT1 350 cast iron 12554290

1994 - 1997 LT1 350 cast iron 10125320

1996 LT4 aluminum 12363287

All 265Ci cast iron 10208890

Part numbers for LT1 and LT4 GM cylinder heads
LT4 cylinder head 12363287

LT1 cast iron 12554290

LT1 aluminum 10128374

Cylinder head gaskets

LT1 cast iron 1992 - 1997 12553160

LT4 1996 aluminum 12551488

LT1 aluminum 1992 - 1997 10168457

The LT4 comes out on top pumping out about 30 more horsepower than the LT1. There really is no interchange as most parts are dedicated to either LT1 or LT4. The gain in horsepower is what we had expected given the changes made. The study of LT1 and LT4 cylinder heads has clearly shown the small block Chevy has evolved into a brand not as user friendly as the first generation small blocks.