My 71 Imperial made it 294K miles without a valve job and was still running smooth but weak when my son rebuilt the engine. Once 87 octane unleaded came out I used it exclusively. Has some pinging but not excessive. Dave ----- Original Message ----- From: "DR CHALLENGER" <drchallenger@xxxxxxxxxxx> To: <mailing-list@xxxxxxxxxxxxxxxx> Sent: Friday, March 10, 2006 12:33 PM Subject: RE: IML: Unleaded or Leaded gas > first year for cats was 1975. > > > >From: "Rob McCall" <Rob_Mopar@xxxxxxxxxxx> > >> > > >From what I've read, the unleaded heads were being phased in for the '72 > >model year, along with the lower compression ratios. By '73 everything > >should have been unleaded. I believe cat converters were phased in during > >'74, and unleaded was mandatory for the cats to live. > > > > > > > > > ----------------- http://www.imperialclub.com ----------------- > This message was sent to you by the Imperial Mailing List. Please > reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be > shared with everyone. Private messages (and attachments) for the > Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx > To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm > > ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm