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#53: 03-30-2013, 11:17 PM
indexing washers
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Originally Posted by pleaidestar View Post
I got my plugs for this trial too, but the plugs look longer than the normal plugs I use in the 2.2..are he plugs the same between 25d heads and 22e heads? Also probably going to order the granatelli wires this weekend, but for now I am at dead end because those plugs look so different.

Glad they are working out for you DOHC. HAVE FUN!
I saw the post by DOHC that they use the same plugs but in case you do have an issue with it, you could always use INDEXING WASHERS to pull the plugs out just a tad. I'm not sure how much difference you're talking about.

Indexing washers are another ignition trick. They're soft brass washer that you put around the plug threads. Normally, you have the center electrode and the "J strap" (ground electrode) - if it is a normal J strap that completely covers the tip of the center electrode, you take a marker and put a line on the plug (or actually since we can't see these plugs in the plug well, we can put on the socket and extension and draw a line with a sharpie on the extension on the side of the plug where the j strap is connected to the plug.

I have to check how the combustion chamber setup is on these boxers but for example if you want the gap to face the piston, you tighten the plugs just snug, then turn them so you squish the indexing washers until you get the black line on top, that way you know the gap on the other side is facing the fuel/air mixture more directly instead of being hid by the j strap.

Here is what I mean - pic is not Hollywood quality by any means

Here is an example for a common inline 4 cylinder motor for example. Black line is drawn on ceramic where the j strap connects to the plug. The opposite side of that connection of the j strap is the gap between that and the center electrode. We want the gap to face the piston so that the fuel/air mixture is ignited best so that the j strap is actually not blocking part of it.

Anyway, the washers can recede the plug a bit but also double as a way to enhance the ignition by having the gap geometry in the optimum place. It is an older racer trick and you can get the indexing washers at just about any car parts store for a few bucks.

Last edited by qiman; 03-30-2013 at 11:23 PM..
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pleaidestar (04-01-2013)