advance springs

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There used to be 3 different vacuum advance cans. One marked 11 gave 22 degrees of advance,this one came stock in 3874876 distributor. So 3874876 with 12 degree base timing and 10 degrees centrifugal advance at 2000 rpm with 22 degree vacuum can ,result would be 44 degrees. Swap can to one marked 8.5 -17 degrees result 39 degrees. Can marked 7 -14 found in trucks,result 36 degrees