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what every boy needs - yeah seriously



 
 
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Old January 9th 09, 05:33 AM posted to rec.aviation.homebuilt
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Default what every boy needs - yeah seriously


First off, we can forget about lost-foam or anything more exotic than
green-sand, simply because there aren't enough of us.


Lost foam isn't all that "high tech" and is actually well within the
ability of anyone that can build their own foundry and ram up some
sand. Classic lost wax is still a viable option and if one uses oil
based sand rather than bentonite green sand you can get much better
detail and steeper angles - but you do need a muller for oil sand.

Here again, borrow a page from the Corvair (or from GM) and we end up
with a 'rocker arm' that actually works. *The tricky bit is that it
does NOT need to be aligned on a shaft... we can literally put a valve
anywhere there is room. *And that means at any angle as well.


My conclusion as well - but if the angles aren't chosen very carefully
we end up with greater than stock side loads on the lifters - thus my
conclusion that we need a new cam at some point or run the risk of
accelerated lifter bore wear. Trying to put a second plug in the mix
and I'm not smart enough to come up with angles that I'm comfortable
with.

Personally I see no need for 2 plugs per cylinder. When was the last
time anyone heard of a spark plug failing with out warning? As for
flame front prorogation, the only real justification for dual plugs
other than unreliable magnetos, we just don't need them on a VW based
engine unless you start thinking high rpm's and a PSRU. But that's
getting too far away from the cheap and simple.


So we make a L-head and an R-head; mirror images. *We do the best we
can with the fins but recognize our limitations and leave the most
difficult of them as CUT fins


If we do the split heads (still need 2 cores, front and rear) the fins
can be rough cast and then finished up on a lathe. The mention of
sawing gives me the idea of using a saw mounted on the lathe for
quicker cutting than a standard tool and maybe even thinner fins. Band
saw off the fins next to the other head and your done. No CNC
needed. My next set of 1/2 VW heads will be done this
way................if I ever get around to a next set.
=======================
Leon McAtee

 




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