Need help on determining LS6 motor

[Fitz]

Originally Posted by Ole Greenie

Square port heads. Not much more to say...it is an LS6.

The swap with a nice LSX is a great idea and I will have to think about it since the LS6 motors have a huge appeal. I kind of like having the only LS6 powered truck around though. You won't find a true LS6 every day let alone in one of our trucks. I plan to occassionally show the truck so it may get quite a bit of attention once complete. The motor only has about 15,000 miles on it so it should last a pretty long time.

Oh lots more to say! Not every square port 454 head was an LS6 head, but no oval port heads were LS6 heads! ALL of the big block heads in the table below are RECTANGULAR PORT heads. The only iron LS6 heads had the following last 4 digits in their casting numbers: 6074, 6492, 4025 and 4026. Only way to know is pull a valve cover and look.

Casting Years CID Chamber CC HP/RPO/Comments
3856208 1965 396 Closed 109cc 375hp/425hp z-16 chevelle
3873858 1966-67 396/427 Closed 109cc 375 L-78
3904391 1967 396/427 Closed 107cc L-71/L-72, 1.72
3904392 1967 427 Closed 106.8 430, 435 L-88/L-89, 1.72 ex
3919840 1967-69 396/427 Closed 107 375 L-78 425, 435 L-71/L-72, 425 COPO
3919842 1968-69 396/427 Closed 106.8 375 L-89 430, 435 L-88/L-89, 1.84 ex
3946074 1969-71 396/402/427/454 Open 118cc 375 L-89 430 L-88/ZL-1 425, 465 LS-6/LS-7
3964291 1969-70 396/402/427/ Closed 109cc 396/402/427/454 large or small spark plug
3964292 1970 454 Closed 109cc 450 LS-6,
3994025 1971 454 Open 118cc 425 LS-6,
3994026 1971 454 Open 118cc LS6
6258723 1971 454 Open . .
6272990 1970 454 Open 118cc service replacement mkIV
10045427 400/454/455 . . Pontiac/chevy aluminium small port /race
10051128 1990-94 454 Semi Open 72cc IP 400cc, bowtie, sym port
12363401 1996-up . Open 118cc bowtie aluminium mkIV gen.V gen.VI
12562934 2000-up 502 Open . gen.VI 502 marine
14011077 1989-94 454 Open 118cc IP 295cc, replacement, C port
14044861 1989-94 454 Open 115 425, 105.0cc, IP 380cc, bowtie, W port
14096188 1970-71 454 Open 118cc service replacement ls-6 markIV
14097088 1991-up 454/502 Open 118 .
24502585 1997 . . . olds/chevy aluminium