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Old 08-01-2012, 09:52 AM
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SBC vacuum too high?

After finding and fixing a vacuum leak under my EGR on my crate stock late 70's era 350 I am now getting vacuum of 25 inches in park, and down to about 22 or so in drive (TH350).

This seems pretty high for vacuum but I have not been able to find any info on what ranges vacuum should be for stock SBC setups. I have read to adjust timing for max vacuum, with mixture screw adjustsments, and I get timing in the range of 32-52* total. The higher the timing I go, the more vacuum I see up until the 50* range. I have it set at 36* or so now but it seems to run smoother with more timing. BTW, this is with ported vac (smog insp. coming up).


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Old 08-01-2012, 10:00 AM
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Whoever told you to do that is an idiot. On a stock sbc you'll want about 14 degrees initial and 36 total (check with vacuum advance unplugged).

Set it there and don't mess with it. Its a stock engine, no reason to "fix it" til you break it.
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