Alfa Pages

[BigAl]

hey guys, for those of you using single point electrode spark plugs.
i just read this, some of you older folks may already know about this.
taken from http://www.carbibles.com/fuel_engine_bible_pg2.html 3/4 way down
http://www.carbibles.com/images/sparkplugkeying.jpg
There's a little known method of squeezing some more efficiency out of your engine, known as spark plug keying. The idea is simple - expose the spark to the incoming fuel-air charge. If the grounding strap on the bottom of the spark plug faces the incoming fuel-air charge, the spark is effectively 'shielded' from the mixture.
Now I know a spark is a spark, and any spark in a fuel-air environment is going to make it burn, but if the spark is facing the intake valves, then there's nothing obstructing the mixture from getting at it. In thousandths of a second, this does actually make a difference to your burn efficiency.
The problem is that when you screw a spark plug into your cylinder head, you have no idea which way the electrode gap is pointing. For best efficiency, it needs to be facing the intake valves or ports as I mentioned above. The solution is pretty simple. Before you install the spark plug, use a marker pen to put a mark on the insulator that aligns with the electrode gap at the bottom of the plug. It's important to use a marker pen and not a pencil because pencil lead is graphite, which conducts electricity. You don't want graphite on the outside of your spark plug conductor!

Once the plug is marked, screw it into the cylinder head remembering that you'll need a quarter turn to snug it up. If the mark on the insulator is a quarter turn from facing the intake valves when the spark plug is finger-tight, you'll know once it's snugged down that the gap will be facing the intake valves inside the combustion chamber.
If the mark isn't in the right place, don't go over tightening the spark plug to force it into position! You can get keying kits which are basically replacement crush washers that are slightly thicker or thinner than the standard one. They come in one-third, one-quarter and one-half sizes, meaning that they can affect how far you can screw the spark plug in by the matching amount. So if you finger-tighten the spark plug and the mark on the insulator is facing totally the wrong way, once it's snugged down it will still be a quarter turn away from the intake valves. By changing the crush washer to a quarter-turn crush washer, you'll be able to get an extra quarter turn before the spark plug is tight, which will solve your problem and the electrode gap will now be facing the right way.


Will the difference in how much the spark plug is further in/out make any difference?
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x2 33 16v
pictures http://www.alfa-pages.co.uk/viewtopic.php?t=5203

[RFlower]

Positioning the plug further out will lower the compression ratio.

If doing so added 0.25cc to the combustion chamber volume on a '33 1.3 engine, the cr would be reduced from 9.5:1 to 9.43:1.

If you're going to worry about which way the plug faces, you might as well worry about that too.
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Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)

[BigAl]

That’s why I asked will the different thickness crush washers really make that much difference. I’m not interested unless it will be beneficial but thought other users might.
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x2 33 16v
pictures http://www.alfa-pages.co.uk/viewtopic.php?t=5203

[john 33_16v]

Hi Al,

Can see the logic here, but guess it only applies to 16v cat cars like ours that use single elctrode platinum plugs, as the rest should be using multi point golden lodges shouldn't they.

I think it would be impossible to see any marker pen marks on a 16v plug 'cos the plugs are so deep and hidden from sight. I suppose you might be able to mark the box spanner and not remove it until the plug is in but that sounds pretty tricky too- oh well.

John
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If it aint broke, fiddle with it until it is!
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93 33 16v Mirtle Met
08 Fiat Grande Punto Exotica Red
90 Yamaha FZR600 Genesis- Silky white/red/blue

[BigAl]

I wonder if racers index theirs, when the engine is out, to make it easy?
Marking the original alfa spark plug tool sounds good, i cant remember if i have ever put a spark plug in with it attached.
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x2 33 16v
pictures http://www.alfa-pages.co.uk/viewtopic.php?t=5203

[lee16v]

I'd have to be sure of a real benefit here as John says that would be a tricky job.

I'm just glad to find the hole and do the plug up without cross threading it really on the 16v.