i have a 76 jet boat with 455. It has an "F" block coding with an engine code beginning w/ "L". I understand this is a marine designator. Also it has "K" heads. It will use an aftermarket intake W/Qjet. I'm looking to rebuild the engine. Any ideas on what direction I should go? I need low end torque and reliable idle. About 350-375 hp and 4500 rpm. It will have water injected exhaust headers. Any opinions on porting and back cutting the valves. Also must run on pump gas. Cost could be an issue. Any advice is appreciated.

 

ID/ Casting
Code Year(s) CID Number Notes
A '65 425 381917?? 1st year, big cars.
386525
B '65 400 389298 442 only, one year only.
D '66 - '67 425 389244 Big-car engine. Toro is different internally.
E '66 - '67 400 390925 442 engine [VERY rare].
F '68 - '70 455 396021 Common big block. Stick type F (sans serif).
F '70 - '72 455 396021 Common big block. Serif type F. Two vertical
and a base serif.
Fa '72 - '76 455 396021 Very common big block. Marine also (L VIN derivative).
G '68 - '69 400 396026 442/Vista/etc. engine.
L '76 455 231788 Motorhome, marine and irrigation. GM made motorhomes
from '73-8, maybe in all? Casting number appears
as "231 [tiny 'L'] 788" on the block. ID/ Use Casting
Code Year(s) CID CCs Number Notes
A '65 400 80 383821 Unique 3/8" stud and nut rocker
425 mounting, using a 3-piece rocker
pivot assembly; all except irrigation
B '65 400 80 383821 Later '65 heads. Some use 3-piece
B '65 425 rocker pivot asssembly.
B '66 400 80 389395 Toro's and 442's got the big [2.072"]
B '66 425 valves. Some use 3-piece rocker pivot
asssembly. "-1" after the casting number
on all B heads after April 21, 1966.
C '67 - '69 425 80 394548 A/C '68 H/O's. Toro's and 442's got big.
455 valves. Rumored to flow the best of all BB
heads. Can still be found.
CA Very small ~3/8" ID lettering.
D* '68 - '69 400 69.75 400370 All W-30. Non A/C '68 H/O's. All '69 H/O's.
All big-valve.
455 69.75 400370
DA
E '68 - '70 455 77,80 403686 455's in general, with 442/Toro's
having big valves.
F* '70 455 80 404438 W-30's. All big-valve units.
G '71 455 80 409100 Generic 455 use, big valves in the
usual applications.
Ga '72 455 80 409100 W-30's, manual 442's used big valves.
H* '71 455 80 409160 W-30's. Big Valve units.
J '73 - '76 455 80,82 411783 All 445's. 'Smog heads',
restrictive exhaust valve pockets.
No big valve units.
K** 455 80 413191
Ka** '73 - '76 455 80 413191 Marine, irrigation, industrial, W-30/Toro,
442 4-speed replacement head. Most were
big valve units.