willie Posted September 21, 2009 Share Posted September 21, 2009 I have a '71SS with no engine. I think i have a chance to pick up a date coded block. My problem is the date code on my trim tag says 12B. When did they change the casting #s from 512 to 289? Did they wait till midnight the 31 of Dec. How can i find this out? Does anyone know the answer? Thanks Willie Quote Link to comment Share on other sites More sharing options...
Dans '70 Z20 Posted September 21, 2009 Share Posted September 21, 2009 Invest in "Chevy by the numbers" book or go to nastyz28.com he has alot of good info on there. Year One's site also has some info and there representatives are also be willing to help you out. Dan Quote Link to comment Share on other sites More sharing options...
willie Posted September 22, 2009 Author Share Posted September 22, 2009 Year One doesnt know when they stopprd using the 512 and started the 289. I have the book it also doesnt state when it was changed over , it just says 70 and 71 have 512 and 72 and up have 289. Maybee someone else out there has a Dec built 71ss. What is your molded block say??????? Help Willie Quote Link to comment Share on other sites More sharing options...
montefrazer Posted September 24, 2009 Share Posted September 24, 2009 A December car is not a late build. Production started late July/early August of 71 for introduction and start of sales in September of 71. December 71 build would be 1/3 of the way through the model build. Sometimes a newer part was used at the very end of the model year, early July built cars, when the current parts ran out, but this would be rare and would not affect all assembly plants. I made frames for 33 years and we would build out the current frames in late June, run some prototype frames for early testing, close the lines for two weeks in early July for retooling, and start running new model frames in late July for shipping to the assembly plants so they could start building the new model cars. Quote Link to comment Share on other sites More sharing options...
willie Posted September 24, 2009 Author Share Posted September 24, 2009 If that being the case then i am looking for a 512 block with a date of Sep, 2nd week thru Dec, 2nd week build molded on block. Am i right? Willie Quote Link to comment Share on other sites More sharing options...
RichG Posted September 24, 2009 Share Posted September 24, 2009 Wouldn't he be looking for a Sept to Dec 1970 casting? The 71 model cars were introduced in Fall 70. A December 1971 car should be a 1972 model car. My 1970 Monte was built in Dec 1969. I agree it should be the 3963512 block, that's what was in my 71 SS Monte. Quote Link to comment Share on other sites More sharing options...
montefrazer Posted September 29, 2009 Share Posted September 29, 2009 You're right, a 72 would have come out in September 71. A 71 in September 70. Quote Link to comment Share on other sites More sharing options...
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