Re:

["I.Mannix" <mannix@privatei.com>]

>Hi ,  here is a dicussion bet. myself and a friend about head porting
>I say that it involves matching the size of the intake/exhaust manifold ports
>to the size of those where they connect to the head, for better air
>flow.  He agrees but thinks something also has to be done to the valves
>when a head is ported.  Opinions???

You're talking about port-matching, technically.  AFAIK, porting in and of
itself does not necessarily include any valve work, but it could mess with
the valve stem castings, if there was something that was determined to be
decreasing flow there.  Sorta depends on the head - things are cleaned up
where needed, and in some cases the runner size is increased.

Port matching typically involves removing material (if any) that is seen
while the gasket is attached to the head, so there is a clean entranceway
for the air leading into the head itself.  On my JH head, there is about
3mm of material to be removed on the exhaust ports, 1-2 on the intake.
Beyond that, I'm not allowed to touch (rules), so I don't know/have'nt
looked.

>
>Also If I get my head ported ( whatever that really means  ) :)  what
>should I have done for street use and how much should I expect to pay?
>Let me know If your estimate is in US or Canadian $$$

My head is costing about $340 USD for machine shop and parts - bolts,
gaskets, coolant, seals, guides, orings, injector seats, etc.  Tool rental
for valve adjustment, too.

As far as "what to do," I'd personally do the following to a "no rules" head:

deck it a LOT, maybe .070".  Heard that you can go as far as .090" off.
The VW specs say the head can measure at a minimum 132.55mm tall, from
block surface to valve cover gasket surface, measured on the back side.
I've measured a lot of heads, seen some that are just about there, seen
some that could go .040".  I am taking mine down .030", should put it right
at the(SCCA SoloII SP) limit.  Supposedly, any more than this screws up cam
timing, but one can account for that - the shorter the head, the farther
"up" the notch has to be on the cam pulley.  I don't think there are any
water/oil passages that get thin by going that far, but I'd be a bit leery
going more than .060-.070".  Just me, though.  I'd use a good 3 angle job,
to increase flow (this might be what your friend is referring to), P&P
typically includes 3 angle, but it is not mandatory.  I'd get it
flowbenched, and clean up the runners a bit, and of course portmatch it.
Use a thin headgasket, get more compression that way.  Should result in
about 10:1 on a JH.  Cool.
>
>Thanks all
>Dave

Hope this helps!


Mannix






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