Date coding explained

[ozbox]

most people would not have any idea how to date code a motor or a part that has the coding on it but would have heard about it..its very easy..
to start i will only explain australian date coding as anyone interested in a sandman, these vehicles will have this system..
what you will see is a number or numbers and a letter and then another number...lets say 28D5..sometimes a d on a motor as a rough casting may look like an O..there is no o in date coding.
anyhow....:errf:
A=JAN
B=FEB
C=MAR
D=APR
E=MAY
F=JUNE
G=JULY
H=AUG
I=NOTHING as it can be confused with the number 1..so they skipped I :Chin:
J=SEPT
K=OCT
L=NOV
M=DEC
the numbers will correspond with the amount of days in that particular month.
so we have numbers first then the letter and the number at the end is.....
the year...so 28D5 is the 28th day of april 1975....

i shall explain later about american date coding....why you ask...:errf:
because gmh used american date coding on its australian motors till llate 1972 somewhere..i just need to verify a date if its known...

[ozbox]

the american style date coding can be confusing if you have been taught the oz way but we shall try and explain as simply as possible...we shall use with permission from scott at concourse parts a couple of pics from his blogspot..we shall use his november 1972 hq ss as a guide...the yankee way worked on month first..then day date..then year..so L242 is november 24th 1972..this system seems to be used on the cast parts like engine exhaust manifolds diff centre section etc and was used from the beginning of holdens engine production till at least december 1972 that we can find out...mr jones if he pops in may be able to give us an exact date...so basically it is the same principal but the australians simplified it..



for more date code type pics in oz and yank versions go here to scotts blogspot
http://hqdatecodes.blogspot.com/

something interesting about the date coding on the early hq is that there is a combination throughout scotts ss that is both types.

[Absinth]

7041240
70 - Prefix for Rochester carburetors


Decade Identifier
7041240

2 - 1960's
3 - 1960's
4 - 1970 to 1975
5 - 1976 to 1982


Year of Manufacture
7041240 Not the model year

6..........1966 or 1976 with a leading 1 in code
7..........1967 or 1977 with a leading 1 in code
8..........1968 or 1978 with a leading 1 in code
9..........1969 or 1979 with a leading 1 in code
0..........1970 or 1980 with a leading 1 in code
1..........1971 or 1981 with a leading 1 in code
2..........1972 or 1982 with a leading 1 in code
3..........1973 or 1983 with a leading 1 in code
4..........1974 or 1984 with a leading 1 in code
5..........1975 or 1985 with a leading 1 in code

After 1975 Carb will have an 8 digit code starting with 1 - i.e; 1704..


Model Federal / California 7041240

0 - Mono-jet........1-bbl........Federal Standards
1 - Two-jets........2-bbl........Federal Standards
2 - Quadrajet.....4-bbl........Federal Standards
3 - Mono-jet........1-bbl........California Standards
4 - Two-jets........2-bbl........California Standards
5 - Quadrajet.......4-bbl........California Standards
6 - Varijet............2-bbl.........Federal Standards


Division7041240

0, 1, 2, Chevrolet
3, Cadillac
4, Buick
5, Oldsmobile
6, 7Pontiac


Transmission 7041240

1,3,5,7,9 - Odd numbers - manual transmission
0,2,4,6,8 - Even numbers - automatic transmission


Notes:
Carburetors produced until 1969 begin with a 702 followed by four additional numbers.
The 5th number is either a "1" or "2," indicating federal (49 state) emissions, or a "4" or "5" denoting California emissions.
The 6th number indicates the division application. "8" is Checker and Marine. The last number indicates the exact application. For the most part, even numbers were used on automatic transmissions, and odd numbers on manual transmissions, but there were numerous exceptions.

For carburetors produced from 1970 to 1974, the first three numbers are "704" followed by the same sequence of numbers as the "702" series of carburetors. (Some 704 carburetors were produced early in the 1975 model run; later units start with "1705.")

1975 and later Carbs
Staring in the 1975 model year, a "1" was placed in front of the "7" followed by "705." The "1705" series of carburetors would run until 1979. Beginning in 1980, the first four numbers were changed to "1708," and this number series would continue until the last carburetors were produced in the late 1980s.

DATE CODE
Most Rochester built Q-jets used a four-number Julian date. The first three numbers are the day of the year the carburetor was built; the last number is the year.
For example:
Carburetor number 17058201 followed by a Julian date of 1238 would have been built the 123rd day of 1978.
One must keep in mind when dating carburetors that the year of production may not always be the same year as indicated by the carburetor number. Quite a few service replacement carburetors were produced. It is quite common to find much later production dates then what is indicated by the carburetor number.

Information from,
"Rochester carbs by cliff ruggles"

[ozbox]

nice add on sean...:D :D

[jennie285]

Our van was built during the 10th month 1977, and the engine number on the block is
19G7 which from reading the codes above should be 19 july 1977 assuming we have read all the info correctly this motor should be near enough, as was built 2-3months previously to being correct. if anyone has any opinions please advise...

Engine number is QR887183

[HK1837]

Also be careful of some SBC stuff as they used I in the early days!

[Blocker]

Engine date code will be found as marked;

[razsandman]

the 4 253 i have here are : 12J3, 18J8, 16G2, 31A9. I think i still have one or maybe two in the back of my dads shed.

how does the coding and numbering system work. how do you match one to your cars manuf date??

[TwoTees]

the 4 253 i have here are : 12J3, 18J8, 16G2, 31A9. I think i still have one or maybe two in the back of my dads shed.

how does the coding and numbering system work. how do you match one to your cars manuf date??

eg. from above
12J3 = 12th(12), 9th month september(J), 1973 (3) or if its blue it may be 1983

i is not used in the month section I think.
This date needs to be near your build date.
There is a thread on it in the technical section.

EDIT: http://www.mysandman.com.au/forums/showthread.php?t=570
Chris

[HK1837]

the 4 253 i have here are : 12J3, 18J8, 16G2, 31A9. I think i still have one or maybe two in the back of my dads shed.

how does the coding and numbering system work. how do you match one to your cars manuf date??

I'd like to see a 16G2 on a red engine!

As before trying to match cast dates is really a folly. You are much better off trying to match engines numbers with cars around it or match your original engine number as close as possible.