OK, I know I might only get about a half of a rat on an excercise wheel's worth of power out of indexing my spark plugs on a 200 six but I'm milking it for all it's worth. Looking down into the spark plug hole from the drivers side of the engine what would be recommended as to what "o'clock" position to have the opening gap pointed to?
1) first take a black marker and mark your spark plug on the side where the ground electrode conects to the plug housing. 2) spin your plug into the head ,check where the mark is when tight you want it so the mark is between 9 and 3 o'clock. what that does is put the opening of the electrode towards the valves, so it ignites the fuel mixture faster,with a bigger spark as aposed to having the ground electrode shrouding the spark kernel.
Some say to put it between the two valve's and other's say to index it at the intake valve to get a more effecient burn. More than like'ly, you will have to have several thickness's of plug washer's, to get each marked plug, at the proper position, in each cyl. Might just try sawing half the electrode ground strap off, or buy a plug that come's that way. Worked well for me in some race engine's, without doing much indexing. JMO
I've studied several pics and think I've got each of my valve locations identified on each cylinder. Would this be the orientation of the open gap if I wanted to index the plugs toward the intake valve of each?
I have heard of this indexing before. It is intresting to try and understand the whole concept. Dumb questions: Are the valves closed when the cyl ignites? Or is the intake valve closing as it's igniting? I thought the intake valve opened as the piston is traveling down then it closed as the piston is coming up and the exhaust valve opens as it is igniting... this is why I thought the gap should point towards the bore
I think it's all a waste of time. When the plug does spark, the piston's still on the way up the bore and you've got a slightly less than fully compressed fuel/air mixture surrounding the plug and electrode at the time the spark fires. The spark is always in the same location, no matter which way the electrode is facing. It's all a placebo effect here.
from what i understand...this is the correct way... ...but...it looks to me like it would better the chance of fouling a plug with the ... low compression...of this engine. ......
I'm pretty sure both valves would be fully closed as the cylinder is heading to the top on the compression cycle, otherwise you'd be losing significant compression.
So where are the valves when it ignites? Isn't the exhaust valve fixing to open when the piston is coming up on the compression stroke? Thus meaning the intake valve is and has been closed and will be closed when it fires?
I've always thought that the valve opening and closing sequence of each cycle begins or ends when the cylinder is at the very top or bottom of its travel and the only thing that happens before it reaches the top is the firing of the spark plug before it reaches TDC. I'm guessing that this lets the ignition of the fuel mixture spread enough so that when it's fully compressed at the top of the cylinder you've already got a pretty good fireball going in there and then when the cylinder is at the very bottom of its travel the exhaust valve is ready to start opening. There's a good animation at http://auto.howstuffworks.com/engine1.htm
Good point there Frank. I always thought indexing plugs was snake oil, although harmless. Since no valves are open when the spark plug fires, it should make no difference where the plug gap is in relation tot he intake valve. However... Maybe if you were to "reverse" index your plugs, as in put the grounding electrode towards the intake valve to shield the inner electrode, I guess you might actually help prevent fouling. Worth the time? I don't know, probably not. I might do it on a six. But on a V8 Mav I'm doing good just to get the damn spark plugs in there at all.
my thought is with a big cam you will get some over lap of the valves where one is opening and the other is still closing but on a stock six or 8. you wont have any over lap of the valves. it might only be worth half a rat power, but i think you would get better power indexing the plug toward the intake valve or at least into the combustion chamber. and it may depend on the design of the chamber in the head. some designs have the plugs near the cylander wall. i think you may lose some power if the plug is indexed facing the cyl wall???? just a thought
Having the spark gap facing the intake cylinder or at least directly between the two sure looks like the combusion will begin taking place more in the center of the cylinder. Take a look at the spark plug position on the underneath of the cylinder head. (photo courtesy of mustangmonthly.com) It looks like a 12 o'clock position aims the kernel directly toward the center of the bore. If the gap was in the 6 o'clock position the grounding strap would not only block the kernel but have it igniting toward the cylinder wall.
I will always index my plugs....whether it does anything or now cause I am funny like that. one more thing: clearance, clarence.
