Victoria! Zeke's CB175 Build
- Thread starter Texasstar
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Texasstar
Can't is a four letter dirty word
"A spark plug for use with internal combustion engines includes a metallic shell housing having a semi-cylindrical shroud partially surrounding the insulator and the center electrode and to which the ground electrode is joined. The semi-cylindrical shroud promotes improved heat dissipation from the ground electrode to the shell housing."Sonreir said:
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Texasstar
Can't is a four letter dirty word
"Heat dissipation of spark plugs with various degrees of thermal endurance in the engine
Nearly 60 % of the heat dissipation takes place through the spark plug case and thread. The seal ring conducts somewhat less than 40 % to the cylinder head. The small remaining percentage flows out through the middle electrode.
The insulator absorbs the heat in the combustion chamber and conducts it into the interior of the spark plug. Anywhere that it comes into contact with the case, heat is conducted.
By increasing or decreasing the size of this contact surface area, it can be determined whether the spark plug conducts more or less heat through the case.
The contact surface area is larger for spark plugs with higher thermal endurance. For spark plugs with lower thermal endurance it is smaller."
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Nearly 60 % of the heat dissipation takes place through the spark plug case and thread. The seal ring conducts somewhat less than 40 % to the cylinder head. The small remaining percentage flows out through the middle electrode.
The insulator absorbs the heat in the combustion chamber and conducts it into the interior of the spark plug. Anywhere that it comes into contact with the case, heat is conducted.
By increasing or decreasing the size of this contact surface area, it can be determined whether the spark plug conducts more or less heat through the case.
The contact surface area is larger for spark plugs with higher thermal endurance. For spark plugs with lower thermal endurance it is smaller."
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the reason they conduct heat is so they can be cooled
the insulator and tip need to run hot enuf to stay clean of deposits
the heat is then conducted back to the head
the design of the plug is this balance to maintain as per diff engines design load etc
the sparkplug is not an aid to engine cooling
the insulator and tip need to run hot enuf to stay clean of deposits
the heat is then conducted back to the head
the design of the plug is this balance to maintain as per diff engines design load etc
the sparkplug is not an aid to engine cooling
Texasstar said:
Rockers vary quite a bit in weight, so I sort through them all and select the lightest and then start lightening them some more.
Those adjusting screws are even lighter after they are drilled and broached to take a hex key (Allen wrench) and there are Ti or Al nuts but watch that they don't come lose. A touch of blue Loctite is needed with Al nuts.
Use Iridium plugs if you can get them in the size you need and start one grade cooler than you think you'll need and then start reading the center electrode and side strap (electrode) for signs of heat.
FYI different fuels burn differently and you need a hotter plug (lower number in NGK series) to burn off the carbon with unleaded fuel. With race gas we use D10 and with street unleaded we use D8s. Check plug length and index the plugs and check for plug to piston clearance. We have to fire notch our pistons to clear the plug.
