I disagree that 1.38 equates to 10.20.. .... Way to many variables involved to make that statement.
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.Compression, suspension, weight, and other factors contribute as well.

That is all true. But IMO, for typical cars 2800-3400 lbs, 9.0-12.0 ET, normally aspirated, no power adders, etc. This equation is a good "target" for the sixty foot. If a car has worse sixty, a converter or gear change may be in order (or other things). Some chassis actually do better, but it may be a case of lots of torque but not enough top end HP (mph). Some bracket racers are not setup to 60ft well, but to just hook up easily and they shoe polish the ET.

Target Sixty Ft = ET x 0.12 + 0.17
9.0 -> 1.25
9.5 -> 1.31
10.2 ->1.39
10.5 ->1.43
11.0 ->1.49
12.0 ->1.61

Wallace is about the same at the mid-lower ET, and slower Sixty ft at the higher ET.

I still use the 60' X 1.56

No you don't... That's the 1/8 mile to 1/4 mile conversion number "1.56". No problem there brother though.

I will recheck the timing for good measure (gear drive). I have only whacked the throttle up to say 2000 rpm in setting the timing.
Whats strange is the car saw no time slip change with short shifting at 6700 or 6000, jet change, only timing change from 42 down to 36 netted me a minus .5 mile an hour
Gonna be looking at the burn at the ground strap on the plugs next if there hot enough

this was a conversion holley blocks in addition a unstable fuel supply.

pump , regulator and recipe changes have been made.