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Ken's built-up Visible Hemi DSC_0552

Ken's built-up Visible Hemi DSC_0552

And a pretty thing it is, too! I'm fairly sure this isn't the old Renwall Visible V8, because the oil filter says "Mopar" and there's a "426" decal on the air cleaner. That would be the famous Dodge / Plymouth / Chrysler Hemi. Looks nice!. The exhaust manifold looks purposeful, not just a cast iron (steel?) tube.

"Hemi" draws attention to the hemispherical combustion chamber above the piston. The angle between the two valves has to be pretty large for a hemisphere shaped combustion chamber, which makes rocker arms between the pushrods and the valves longer and more complex than the typical compromise combustion chamber in a 2 valve, pushrod, 4 stroke engine. That complexity is the cost. The heads are large because the valves go in and out, not merely up and down, and it is big, has a large volume, because its full of stuff.

The reward is a compact combustion chamber with a relatively small surface area and relatively large volume, The distance the flame front has to travel from the spark plug to the furthest edges is relatively short. And when a valve opens, the fuel/air mix coming in or the exhaust gasses going out don't have to go far to get the job done. The angle between the intake and exhaust flows promotes mixing and evaporation of fuel droplets into combustable fuel vapor. And the small surface area minimizes the heat radiated into the mixture by the head. valves and piston, making detonation / knocking / premature ignition less likely.

I'm presuming the big, red, vaguely heart-shaped bit directly behind the fan is the water pump, and the smaller red bit behind the oil filter is the oil pump. So what's the bright silver business with a big pipe and a little pipe, and the dark gray pulley and adapter? Power steering hydraulic pump? Air pump for thermal reactors to burn up hydrocarbons that otherwise might escape? Air conditioning compressor? Guess I have to check the manual!

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Photo taken on 3 February 2018 (© wbaiv / Flickr)

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