Spark plugs Options

[ruddyboys]

Have to change spark plugs this weekend. I went to 3 FLAP and none of them carry Bosch W7CC. They have the usual AC Deelco, NGK, champion etc. Are any of these any good or should I stick to the Bosch? If Bosch is the best bet, who has the best price and shipping?
Thanks

[Rand]

I hope this isn't hijacking, but it reminds me of a question about twin plug engines. How does that really help? If multiple electrodes are a waste (which I agree with), why are multiple plugs effective? If it combusts, how does it matter where it started? Or how does it matter if it starts in more than one place (if that's even possible once it started)? It's in the same chamber and combustion is combustion, right? Sorry if it's a dumb question, but I've never heard the answer.

[Dave_Darling]

I hope this isn't hijacking, but it reminds me of a question about twin plug engines. How does that really help? If multiple electrodes are a waste (which I agree with), why are multiple plugs effective?

The whole charge does not just suddenly burn. It takes time for it to all burn. If you start the burn from two separate locations, the burn happens faster and in theory more evenly. The rule of thumb in 911 engines is that you can run a full point of compression higher in twin-plug engines than single-plug ones.

Modern cylinder head design makes twin-plugging less beneficial, as more care is taken to get the chamber shape to work optimally with the spark plug placement.

In some applications (e.g., aero engines) the two plugs are there for redundancy. Because if one spark fails while you're in the air, you really really really want to have another one there to light the charge.

--DD

[Mark Henry]

I hope this isn't hijacking, but it reminds me of a question about twin plug engines. How does that really help? If multiple electrodes are a waste (which I agree with), why are multiple plugs effective?

The whole charge does not just suddenly burn. It takes time for it to all burn. If you start the burn from two separate locations, the burn happens faster and in theory more evenly. The rule of thumb in 911 engines is that you can run a full point of compression higher in twin-plug engines than single-plug ones.

Modern cylinder head design makes twin-plugging less beneficial, as more care is taken to get the chamber shape to work optimally with the spark plug placement.

In some applications (e.g., aero engines) the two plugs are there for redundancy. Because if one spark fails while you're in the air, you really really really want to have another one there to light the charge.

--DD

(IMG:style_emoticons/default/agree.gif)
The burn is like a wave, if it starts on one side it takes time to get to the other side.
If it starts at two points the wave from each point only has to travel half as far.
The more efficient the burn the higher CR you can run.

Modern heads the plug is in the center surrounded by 4 valves, like Dave said better chamber and piston top design, plus water cooled can run higher CR and leaner AFR due to more efficient cooling.

[brant]

I hope this isn't hijacking, but it reminds me of a question about twin plug engines. How does that really help? If multiple electrodes are a waste (which I agree with), why are multiple plugs effective?

The whole charge does not just suddenly burn. It takes time for it to all burn. If you start the burn from two separate locations, the burn happens faster and in theory more evenly. The rule of thumb in 911 engines is that you can run a full point of compression higher in twin-plug engines than single-plug ones.

Modern cylinder head design makes twin-plugging less beneficial, as more care is taken to get the chamber shape to work optimally with the spark plug placement.

In some applications (e.g., aero engines) the two plugs are there for redundancy. Because if one spark fails while you're in the air, you really really really want to have another one there to light the charge.

--DD

(IMG:style_emoticons/default/agree.gif)
The burn is like a wave, if it starts on one side it takes time to get to the other side.
If it starts at two points the wave from each point only has to travel half as far.
The more efficient the burn the higher CR you can run.

Modern heads the plug is in the center surrounded by 4 valves, like Dave said better chamber and piston top design, plus water cooled can run higher CR and leaner AFR due to more efficient cooling.

additionally...
when the factory started twin plugging their race motors.. they were pretty small bore
the 2.o pistons and combustion chambers on a 6 cylinder were a different design and shape than the later motors

so the tall piston shape was another barrier for the burn to cross... making the twin plug a great solution to start the fire on both sides of the pistons "ridge" or tall center

I believe starting with the 2.2, the combustion chamber was re-shaped and the piston as well, to help address this issue and assist the burn front in completing its job...