Looking for more pep off the line

Alecb said
Hey all,
I've got a 73 Duster with a 360 LA and 727 that I rebuilt myself, and I'm looking for suggestions to make more power down low. The engine is bored over 0.040, has KB 107 pistons, 9.6:1 compression ratio, stock crank and rods, Summit K6901 camshaft 218/228 0.441 lift, stock J heads, stock cast iron intake, Holley 600 cfm vacuum secondaries, TCI 141500 converter, 3.23 rear gears, timing set at 12-15 degrees BTC. My build is meant to be a street machine on a budget, it runs well but it feels a little lacking off the line. Any suggestions for making better power would be much appreciated.

I concur with rumblefish post #6. With your displacement and intake valve size, the tighter the LSA the better. 105° would be good if you can get a cam grinder to do one that tight. 108° would be sortof acceptable.
Richard Holdener did a youtube video comparing on the dyno three LS cams on a 6.0l, I believe. He had Crane grind four cams, all with the same lobe profiles. The difference was LSA; 108°, 112°, 116° and 120°. Note that the General uses a cam with 122.5° LSA to keep a smooth idle. That wide LSA also flattens the torque curve and extends it, at the expense of the bottom end.
Richard dynoed the 120° LSA cam first. When they installed and dynoed the 112° LSA cam, the engine picked up about 35lb/ft torque between 3500 and 4500 RPM but lost a few above 5500 RPM. When the 108° LSA cam was installed it picked up just a few lb/ft over the 112° cam. Now this engine was built with LS3 heads that flow real well. Your heads do not flow anywhere close.
I do agree with the guys stating tuning is required, and will get this engine performing. The wide LSA tends to flatten the torque curve, so it will never have the snap a shorter LSA will give.
Another thing to consider is valve lift. At 0.441" it is mediocure these days. I would check intake valve to piston clearance and consider stepping up .1 on the rocker ratio. This will get the valve off the seat quicker which helps. In addition you would pick up probably 0.025" lift. I expect your heads flow would top out around 0.500", so getting the valve lift closer would benefit getting air/fuel into the cylinders.

Mattax said
I generally discourage relying on voltage measurements at the coil because they will vary depending on conditions.
For example, Engine off, key in run.
Power supply voltage will be roughly 12 if the battery is in good shape.
Current at coil will be much under. How much so depends on the connections and the alterator field draw.
Also with the ECU ignition, its like the points are closed all the time when key is in run, engine off. So current flows thorugh the resistor full time, making it hotter (and higher resistance) than when running.

When driving, power is supplied at roughly 14 Volts, current flows through the resistor on/off. So running there is a higher voltage supplied to the system plus cooler resistor - and more so at higher speeds.

Some things to check.
Engine off. Resistor should be .5 to .6 ohms
Engine running. Voltage supplied to resistor compared to overall system voltage should nearly the same. Alternator output voltage should be around 14 V, and the voltage at the resistor should be within a 1/2 volt of that.

Its best to do these measurements when the battery fully charged. The ammeter will show whether its recharged or not. It should be finished recharging within a few minutes of starting. If not, charge the battery on a charger and try again.