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Originally Posted by GeneBob
The higher compression head improves the efficiency of the engine some so less fuel goes to waste heat and more goes into useful power.
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This really does not make an engine run cooler, ...actually it makes the engine run hotter due to more fuel being completely burned inside the combustion chamber -and thus creating more BTUs. The major reasoning behind a high-compression head running cooler is the roof of the combustion chamber is lowered which allows for for water passage capacity above the hottest portion of the chamber. This allows for better heat dissipation into the (additional) water.
Quote:
Originally Posted by Model A Ron
GeneBob
You are right that I am paying more attention to it. With the stock head I ran 1/2 advance and bumped it a few clicks down when I went over 40 and just above full spark advance between 45 and 50. The weather was 10 to 15 degrees cooler and my Motometer would be between 1/3 to 1/2. Now its showing 1/8 maybe a tad bit more but not much at all.
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It has been my experience that preignition sounds on a L-head (flathead) are different sounding than an OHV engine, therefore many people never recognize a squeaking noise that is the sound of detonation. I would suggest for the interim until you are very familiar with your vehicle's engine, that you step up to using mid-grade or premium fuel. You can probably get away with 5° degrees or so of more advance when using a fuel with an octane rating over 90. This should put you into a safe zone until you have 3-4 thousand miles on your vehicle and can discern a change from normal if you were to use a lower octane fuel.
With regard to your Motometer readings, I am going to suggest reading above about increased BTUs and below about Motometers. It has always been my experience (...and we have installed a bunch of H/C heads over the years) that just installing a H/C head does not drastically lower water temps to the level you are suggesting as indicated on your Motometer. Something else changed if that is happening.
Quote:
Originally Posted by jayvee34
I have the centrifugal advice ( advance ???) in my car so I don't have mess with my spark control, but my car does run cooler with the 5.5 head. Here in Florida we are seeing the high 90's degree and an occasional 100 degrees. My Moto Meter shows about 1/4 red on the road @ 45 to 55 MPH and just showing red @ speeds below 45 MPH. Love it.
John |
Again, the high-compression heads do run cooler simply because of more water capacity, ...and not really because of a centrifugal advance.
John, I realize a Motometer is a unique novelty however they are about the worst temperature indicator that someone can use. Most people experience the similar readings with their Motometer simply because at higher speeds/RPMs, the water pump is slinging more water upward into the upper water tank. At those higher RPMs, that water actually splashes onto the bulb of the thermometer which creates a higher reading than just water vapor & air that is surrounding it at lower speeds.
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