>I have a big valve head, so I have to index if I use the extended nose plugs. One of the things I've heard mentioned, is that indexing allows you to >orient the electrode/gap so as to allow the best combustion. Agreeing that the orientation should be 180 dgrees off the oversize intake valve, left to >my own devices, I would tend to put the open space toward the center of the combustion chamber. Does that make sense?
If you buy into the notion that indexing is going to gain you some performance (I'm not sure I do, or that it would be noticeable), then I think it's contradictory to where you'd want to index things to avoid valve contact. Indexing for performance would seem to indicate that you want the gap facing towards the intake valve. Or, as Ken suggests, facing away from the intake valve. Flip a coin as to which is best for an Alfa motor. Then toss both of them to the wind, because indexing them that way will maximize the chances that you'll contact the valves. To avoid contact with the valves, you want the plugs indexed for/aft. Personally, I think you're worrying too much over something that won't make any difference you'd ever notice. And as Les says, if you did index them 'optimally', but the spaces moved the plug that much further back from the combustion chamber, would you still reap the benefits? On my big valve Spider, I mark the plugs, then shuffle them around so I get the best combination of fore/aft orientation to void valve interference. On every other Alfa I own, I don't bother with any of the above. bs -- to be removed from alfa, see http://www.digest.net/bin/digest-subs.cgi or email "unsubscribe alfa" to [email protected]
