Hello all,

Just rebuilt the 350 from my 72 cutlass and had it tuned in Colorado Springs, CO. Recently I moved to Kansas so I upsized from size 64 to 66 jets, but it seemed like it lost a little ‘pep’.

Put in the 64s back in and retuned it and it still doesn’t have as much power as it did in the springs. What do you think could be the issue?


The motor is bored .030 over, and has higher compression and a very mild cam upgrade. It had/still has a Holley 600cfm avenger.

 

Is the gas in your area E-10? That will cause reduced power due to the lower energy content of the alcohol.

 

You'll need to re-establish the correct A/F mixture ratio (needles/screws). Best done w/ a vacuum gauge.

 

Vacuum gauge really? You can only do that at idle, useless.
Buy a wideband and tune it right.

 

Completely disagree it’s useless. Completely agree the ‘absolute’ best is a wide band esp. for WOT.

 

Cruise, off idle and a host of other running parameters are best suited to using a wideband. Vacuum gauge only helps at idle, that’s it.

 

I’m with Mark on this one. Granted, for decades, tuners found ways to dial in carbs with basic indicators but wideband is the best we everyday people have at our disposal. You can clearly see transitions between circuits, optimize them as the architecture allows, then observe the effect of the changes in real time or in some cases, logged. You can’t see tip in, accel pump, cruise, power, momentary rich/lean anomalies and definitely not WOT with a vac gauge at idle. Setting idle mixture based on vac is a decent way to get started on carb adjustment but in my case, I need the wideband readings to get the rest, even idle for that matter.

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