National 1970 Chevelle LS6 Registry LS6 Engine Codes / Casting Dates

Engine

Transmission

Notes

Code

Size-Carb

HP-RPO

   
CRR 454-4 450-LS6 TH-400  
CRS(1) 454-4 450-LS6 (w/L89) TH-400 Aluminum Heads
CRV 454-4 450-LS6 Manual M22  
CRX 454-4 450-LS6 Manual M22 Heavy Duty Clutch
CRY(1) 454-4 450-LS6 (w/L89) Manual M22 Aluminum Heads/Heavy Duty Clutch

(1) There is some discussion about the 454 being sold with aluminum heads. One very respected source says that according to records at Tonawanda, no 454 engines came with aluminum heads. Their records indicate the L89 option was cancelled (not replaced) with the demise of the L78/L89 396 (402) engine combination. On the other hand, some have reported seeing the CRS code on engine blocks and one registrant here has a dealer bill-of-sale plus the warranty protect-o-plate card both showing the CRY code.

Engine Specifications:
454 cubic inches
450 horsepower @ 5600 RPM
500 pound-feet torque @ 3600 RPM

Block ~ Casting number 3963512
* Bore ~ 4.21"
* Stroke ~ 4.00"

Heads ~ Casting number 3964291
* Closed chamber square port cast iron
* Intake valve size ~ 2.19"
* Exhaust valve size ~ 1.88"
* Combustion chamber ~ 109.037cc
* Castings used both "N" and "peanut" plugs
* Compression ratio ~ 11.25:1

Carburetor ~ Holley
* List 4491, 454 (CA), S/T, #3967479 GM
* List 4492, 454 (FED), A/T, #3969898 GR
* List 4556, 454 (CA), A/T, 3969894 GP
* List 4557, 454 (FED), S/T, #3967477 GG

Intake Manifold ~ Casting number 3963569
* Aluminum low-rise. Carburetor is 1.25" above cylinder head ports.

Exhaust Manifolds ~ Used on other Chevrolet models and other years
* RH ~ Casting number 3916178
* LH ~ Casting number 3909879

Distributor
* Stamped number 1111437

Camshaft
* Same camshaft used with 402/375hp engine
* Casting number 3904366
* Part number 3904362
* Mechanical lifter
* Intake & Exhaust lift .520"
* Intake duration 316 degrees
* Exhaust duration 302 degrees

Crankshaft ~ Casting number 3521
* Forged steel
* Stroke 4.00"

Casting Dates
* The following is applicable to cylinder heads, engine blocks, intake manifolds, exhaust manifolds, and water pumps.

A - January B - February C - March D - April
E - May F - June G - July H - August
I - September J - October K - November L - December

* The following is applicable to alternators, distributors, and starter motors. Note electrical items did NOT use the letter "I" because it could be easily confused with the number "1."

A - January B - February C - March D - April
E - May F - June G - July H - August
J - September K - October L - November M - December

Holley Carburetor Dates

Holley Three-Digit Date Codes - Through 1972

1st Digit

2nd Digit

3rd Digit

Stamp Year Stamp Month Stamp Week
5 1965 1 January 1 1st week
6 1966 2 February 2 2nd week
7 1967 3 March 3 3rd week
8 1968 4 April 4 4th week
9 1969 5 May 5 5th week
0 1970 6 June    
1 1971 7 July    
2 1972 8 August    
    9 September    
    0 October    
    A November    
    B December