OK OK, I know the gains would most likely be very minimal in a DOHC application, but has anyone tried it? I've read to index them with the gap towards the intake valves on our engines. Is this correct? Truth is, I've been bored lately with my broken hand and thought it would give me something to do for a while, but I need to know what direction they should face and where to find the indexing washers. Summit doesn't seem to carry them. Thanks for any help BTW, I came across an article where TOO mentions indexing a D16, which made me think it might be even just a little worthwhile.


[Modified by SpecR0123, 5:38 PM 8/8/2001]

 

Indexing plugs usually involves using indexing washers of various thicknesses to get the "open" face of the spark plug to face the correct direction. This was an old drag racers trick that was used on carbureted cars. Todays fuel-injected higher compression cars with advanced head designs see minimal (if any) gains to indexed plugs. The washers also cause the electrode to sit higher up in the combustion chamber away from where you want it to be.

In other words - don't bother

 

Hey Big Phat R talking out your butt again! Wrong, there is no difference between the effects on a carbureted engine and an injected engine. The intended principal is to get maximum spark to the area where the top of the piston and the combustion chamber compress the charge. By aligning the open end of the plug to this area the spark is not shrouded by the ground electrode. Which has not changed with newer injected engines. And by raising the plug you eliminate the chances of a hot spot caused by the plug threads extending into the combustion chamber. This means open area of the plug electrode gap facing the exhaust port on most Honda engines!

 

Thanks, but what direction should the plug be indexed on a B series head? Also, any ideas on where to find the washers?

 

Like I said and this is true for B series heads "This means open area of the plug electrode gap facing the exhaust port on most Honda engines!" Moroso makes the washers should be under $15.00 for an assortment of thickness. Part number 71910, do not use 71900.

 

i disagree.

the head design of a modern fuel-injected cylinder head will have superior mixing abilities and hence inherently have better combustion of the air/fuel mixture - in addition to that modern fuel-injected engines have better ignition systems compared to carbureted engines which would negate the effect of the 'shrouded' electrode. you talk as if the shrouding effect is large - this is wrong. the air/fuel mixture is not static during the period of compression, it is actively flowing over the electrode area and thus is in direct contact with the source of ignition the entire time.

you said "the intended principal is to get maximum spark to the area where the top of the piston and the combustion chamber compress the charge" - duh! of course that's the intended principal.....that how internal combustion engines work Einstein. you consider this a revelation? I don't and I don't understand why this is a point of contention. Similarly, if raising the spark plug out of the combustion chamber decreases the chances of hot spots - why didn't they manufacture the head this way to begin with? that doesn't make sense. you're implying that the stock configuration is inferior.

My point is that the difference is negligible, nothing more.


[Modified by Big Phat R, 12:03 AM 8/9/2001]

 

The mixture has little to do with it; it is the location of the compressed charge. Look at the shape of your pistons and look at the shape of the combustion chamber. Ever heard of quench pads and the location they force the charge in too during compression? Da! For the uneducated a large portion of your piston dome! I guess I must be Einstein! Do you really believe the air/fuel charge is evenly dispersed through out the combustion chamber durning compression and spark ignition?





[Modified by DB1-R81, 12:32 AM 8/9/2001]

 

Ahh... it's all crystal clear now that you have explained it so eloquently