Date: Mon, 9 Dec 1996 18:00:17 -0800 (PST)
From: Mike West <mwest@cdsnet.net>
Subject: Porting the Single Ports


 Porting a single port is almost a joke in itself, I suspect.

 The big bottle-neck is the intake port.

 Still there are some areas under the valves I didn't like.

 Sharp corners on the outlet or inlet side. Where the hole was bored 
thru the casting for the valve seat.

 The sharp edges are a pressure drop zone. They cause turbulence.

 In one of my books they speak of a "window" to open up.

 You look down thru there and you can see out the outlet or inlet.

 That's the "window". It's just an oval shaped light at the end of the tunnel.

 There are a couple of edges under the valves that are sharp and are
the side of this "window".

 I broke those edges with a carbide burr, about 1/8"(3mm) and smoothed 
some other sharp spots out.

 The carbide burr works great on the aluminum, certainly no clogging etc.
and fast cutting.
 In a drill doing 1200 rpm you are millimeters away from destroying 
the valve seats.
 I had taped the seats with masking tape just in case.

 "Just in case" was happening way too much so I got out of there and 
went to a Dremel tool. It's much more polite.

 Use the pink stones on aluminum, it still clogs but not so bad.
Use the grey stone to dress the pink stones with.
 Nobody knows what they're made of or best for they just sell them.

 Someone said "practice on an old head first". (not a local guy)

 That's not just advice, it should be in the Bible, Torah and Koran.
It may be there, it just got interpreted wrong.

 You will probably destroy a head the first time.

 I didn't but that's because I'm old and have already destoyed many
valuable things. And I chickened out.

 I'll go on and do some mediocre polishing in the chamber area, these
had some hefty pits in them. Localized corrosion.
 I just want them smooth enough that carbon can't build up too easily.

 Lets say "brillo pad" in the chamber area.

 The inlet I'll give the "frosted" look.

 The exhaust ports are already twice as big as the inlet, so they just get
the "deburring".

 Since I am trying to squeeze the last bit out of these heads, I went
and rounded up the inlet manifold and will work it over and then match
the head inlets to it.

 If I had the tools etc., I think I'd make a square inlet manifold
and "square" the inlet orfice to match. I could probably get 20% more
out of them.

 But if I had the wherewithall to do that, I'd just go buy a set of 
double ports. I'm just poor right now,(temporary) not stupid.

 All in all, I may have picked up a few percentage points.
I'm not sure it's worth the risk of damaging a set of heads.

 Dual Ports look like they could be improved and get great things 
from them. That's just an opinion from looking at them and the data
in the Bill Fisher book, "Hotrod a VW. . .".

 All the stuff I've layed on you about those valve guides leaking.
It was very apparent in these heads after I got the valves out.

 Carburized oil in the inlets and outlets. I would have thought it
would be burned out of the outlets.

 Short trips ? poor combustion? who knows.

 I've been reading again.  :-)   

 We need some 4 valve heads.

 Those guys are getting 1+ horses per cubic inch.

 The 1600 would crank about 96 hp.

 Maserati with a 6 valve turbo-charged is getting 2.13 hp per cu. in.

 That would be 204 horsies out of a 1600.

 We could out-run the smog police !    :-)

 west