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#1
03-13-2022, 02:41 PM
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455HO tuning issues
I have a 72 T/A 455HO/TH400. Engine was rebuilt by the previous owner. Now running a Comp 268H cam. Heads were massaged to get compression to about 9.2:1. Stock converter. Stock points style distributor with Pertronix internals. Just had the Quadrajet rebuilt by Ray Klemm, highly recommend Ray if you need your carb rebuilt.
After reinstalling the carb, it runs much better, but I cannot seem to get it tuned and dialed in. With the vacuum advance unplugged I set the initial timing at 11*, it seemed to be happy there, with the idle at about 1100rpm. When I plug the vacuum advance in the timing jumps up to almost 30* and the idle jumps up by 300-500rpm and the idle seems to bounce around a little. I checked the vacuum, it pulls about 15"hg at 1100rpm, with the vacuum disconnected. With it connected it bounces around from 12-15". With the vacuum advance connected to full ported source, I have to have the idle set around 1300 rpm to maintain enough to idle at 750 in gear, and even there it surges a little. Any suggestions on what the issues are?
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1971 Trans Am - Sold 1977 Can Am - Sold 2002 Trans Am Firehawk - Sold 2004 GTO - Sold 2006 GTO - Sold 1970 GTO - Sold 1972 Trans Am - Sold 1970 Trans Am - Current Project |
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