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Reply to "Twin plug"

@edsnova posted:

Oh man, that does look like trouble: a potential hot spot that could effectively undue the benefit of the second spark.

Could more material be welded in there, then drilled and tapped and ground back even to reduce the sharp edges and keep chamber volume consistent?

This particular head is a mess in so many ways that it's hard to know where to start. There's no quench pad on the side the 2nd plug comes in on. My guess is that this particular setup was for an aircraft engine, for ignition redundancy. There's no way that thing is an improvement in any way over a stock 043 VW head.

But if you recall me saying that a guy who said he'd done "dozens" of twin plug conversions wrecked a set of Super Pros for me about 7 or 8 years ago-- this was what he did. The angle he came in on left 2 or 3 spark-plug threads exposed in the chamber on one side. More significantly, he broke through the quench pad.

In theory, the chamber could be welded up and reshaped so that no threads were exposed, but that messes up the swirl in the combustion chamber which is the entire point of the exercise.  The chamber above (and my Super Pros) is a lost cause because if the head had a proper quench pad, the plug would come out right in the middle of it.

It's harder than it seems at first blush.

Last edited by Stan Galat
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