Is my 340 Overcarbed? Avg 5-6 MPG

smartken22 said

OK I just got back from Pep Boys and picked up some 69 and 68 jets as well as some 81 and 82 jets for the secondaries. Do I need to plus up on the secondary to richen WOT out? I will try and mess with timing again, but the more I would advance it, it would start pinging badly. The most I could get was 18 degrees. I checked the bushing in the dizzy and it is a black one so I am as big as I can go there. If I keep my timing at 18 degrees initial that would bump my total up to 36. Does that sound right?

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IMO you're going in the wrong direction you need to be looking more at your power valve... Read these steps carefully and your car WILL run better:

1) STOP jetting down! In fact go back to where your WOT was closer to 13:1 or less
2) Change the mechanical advance bushing for less advance; I think the next one down is 18* see if you can go even more than that. You want like 12* ideally so that...
3) You can set the initial advance to 20* or so where it should be 14* is way too little and end up with not more than 32-34* total advance.

You're getting ahead of yourself here tuning Holleys isn't only about swapping jets so take a step back and carefully re-read what everyone has been telling you in this thread regarding timing and target A/F ratios.