[stillsearching]

What type of combustion chamber is most suited to low rpm's, something off the shelf? Lots of engines seem to idle fine - I haven't tried putting any under load. I wouldn't even know where to begin with different shapes though... maybe Vortec type ones with their swirling to help keep the mixture tumbling longer since piston speeds are slow?

Engine size may not always be a problem - one of my experiments would be for a stationary engine, low rpm lets me make an engine last much longer, but yes i'd like to also use it in a car/truck too. One engine i'd like to try this on is based off the olds 455 - pretty tall deck height, long stroke, long rods. Those engines were known for high efficiency (for what they were) already - 15-20mpg on the highway (driven american style, not ecomodder style), no overdrive, carbureted in the 70's in full size sedans was something no 454 chevy or 460 ford or 440 dodge could ever touch. One plan is an Olds 427 - the 4.25" stroke 455 crank in an early 400 4" bore block. Another is a cut down Olds 425 crank 3.975" stroke in an Olds 260 V8 diesel block 3.5" bore but thats more work for less benefit. A second reason for wanting the Olds is that ALL heads interchange - meaning I can put the tiny 260 small block heads (which are already small for low rpm on that) on the bigger 427 - this should match my desire to turn really slow, likely making the torque peak below 2000rpm.

Is there any way to alter the "lugging" issue of torsional vibrations, to change the resonant frequency at which that happens? Heavy flywheels or would that have no effect? Different crankshaft counterweighting? I don't understand the physics of what causes it, but I have felt it so I know what it is. :-/