Re: [T3] Lead-free fuel

["Jim Adney" <jadney@vwtype3.org>]

On 13 Mar 2001, at 14:50, Dave Campen wrote:

> I've noticed recently that a number of parts shops are selling new Mexican
> heads with a long-reach small diameter spark plug, and smaller valve sizes.
> These heads are definitely made for lead-free fuel and presumably should
> resist cracking better as well. I suppose the small valves would make them
> less suitable for a tuned engine, though.

The space between the spark plug hole and the valve seat is the 
weak point on these heads; that's where they crack. Making this 
area thicker by going to a 3/4" SP thread should be a big help and 
is something that I've heard of several suppliers doing, but I've never 
seen one. If you also make the valves smaller that helps a lot also, 
but also cuts down on the engine's breathing. Considering that 
most of the sales for this kind of head are to the high performance 
crowd, this seems like a counterproductive way to go. Rather 
strange.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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