From: John De Armond
X-Source: The Hotrod Mailing list
Date: Aug 1992
Subject: Re: Head Porting Tools
>Well, I'm about to embark on a head porting/polishing project with my GN
>heads. I think I have most everything I need but would appreciate some
>advice on bits for my air powered die grinder.
>I plan on using carbide bits ... what bit shapes should I look for? I
>assume a couple long shaft bits will be desirable? Do I need the bits
>with the grinding stones (my experience has been they wear down VERY
I have several tulip shapes, a couple of sizes of cylindricals, a couple of
cones and a variety of rounds. I also have a large, thin disk cutter that
is rare as hen's teeth but is invaluable for doing two stroke transfer
I'd not spend too much money on extended shank burrs. They are seldom
truely concentric and are very easy to bend. Very expensive too. I have
one long shank ball that I use only occasionally. You'll be much happier
with an extended collet die grinder.
A couple of other tips. For polishing, get some 1/4" drill rod and carefully
slit the end with a dremel cutoff wheel or similar. Emory cloth can
then be inserted in the groove and wrapped around the drill rod. It forms
a very efficient "flapper" that cleans itself by wearing off. Use drill
rod because that is about the most straight and true material you can get.
Use your fingers to keep the emory cloth tight on the rod. I start the
grinder spinning with my fingers loosly around the cloth and then push
the end through my fingertips into the port. Unless your fingertips are
scarred and semi-numb like mine, you might want to wear a thin leather
glove on your off-hand.
Run the grinder as fast as you can when using carbide burrs. something
the dentists figured out a long time ago - the faster the burr, the less
the vibration and the smoother the cut. I run my shop air at 175-200 psi.
My strob-o-tach says my 30,000 RPM is turning close to 60,000 RPM.
Does it shorten the life? Dunno. I bought my Black & Decker industrial
die grinder in 1970. I put a spindle bearing in it last year because the
fumes from the fire rusted it. Vanes and rear bearing look great.
Sooper Secret (TM), something I'd not tell just anyone. :-) the key to
a fine finish and a long and harmonious burr life (some of mine were bought
along with the grinder) is to continuously mist-cool the burr with
an appropriate cutting fluid. I apply it with a device called "Nu-mist".
This is a small plastic can with an aluminum manifold on top and a small
hose ending in a nozzle. The hose is concentric. One side carries low
pressure air and the other the cooling fluid. Mine came from
Grangers and had a stock number of 4Z562. don't know if it is currently
available or not. the nozzle is small enough that it can either be taped
to the grinder or held nearby with an umbilical dial indicator stand.
The other half of the secret is cutting fluid. For ferrous metal, absolutely
nothing is better than 1,1,1 trichloroethane. It gets involved chemically
in the cutting process, though I don't know the details. Obviously good
ventillation is needed. For aluminum, ordinary antifreeze mixed just like
for your radiator is the best. Use these on taps and dies too. If you've
ever bought that high priced Tap-matic tapping fluid, these two substances
are what you are really buying.
Finally, if you chip or dull a burr, don't throw it away. It can be
electrochemically resharpened for a nominal charge - usually around $8.
Your machine tool supplier should be able to point you in the right
direction. Zieglers here in Atl advertises resharpening services.
From: emory!chaos.lrk.ar.us!dave.williams (Dave Williams)
X-Source: The Hotrod Mailing list
Date: Aug 1993
Subject: cylinder head mods/porting
-> chamber. It seemed that rounding this long corner off would help cut
-> down the
-> turbulence in the combustion chamber a little. Is that a good thing
-> or a bad thing?
Generally it's bad. You want as much turbulence as you can get -
that's one reason you have a quench area in the first place. Take a
look at some pictures of professionally-ported heads and you'll see they
try to keep that sharp edge.
-> Anyone else done much porting?
Does that pile of burned-out Moto-Tools give you a hint? <grin>
Even the big 1/4-hp die grinders get too hot to hold after a short time.
The real solution is AIR! Yes, an air die grinder has its problems too
- sure, they're lighter and blow the shavings away, but instead of
blisters you get frostbite.
[Yup. Just retired my very first grinder that I bought in 1969. Black
and Decker (back when they made actual, usable tools) made the beast
but they quit stocking spare parts for it. This'un is like the old
farmer's ax. 4 or 5 sets of vanes, a couple of sets of bearings,
3 or 4 collets but it still a good old grinder :-) The important
things to look for are speed (the more the better) and smallness
of the collet. A good collet is no more than 1/2" in diameter.
My B&D was rated at 35,000 RPM @ 90 psi but clocked out according
to the Strobo-tach at 60,000 on 175 psi air. They say don't do it
but what hotrodder has ever followed the instructions? :-)
A 1/8" pencil grinder is very handy. It will do all those things
the electric ones promise but can't deliver.
Carbide burrs, of course. Never waste money on anything else. They'll
last a lifetime if you don't bend 'em and can be resharpened. At least
a few long shank burrs are necessary. At the minimum, a ball and tulip.
Several companys that advertise in Circle Track and the likes sell kits
of burrs very reasonably priced. Expect to pay at least $15 a burr,
typically $20. Avoid being talked into getting "aluminum burrs" even if
you're doing aluminum. These have great gouging flutes that take pounds
of metal off at a time and leaves a finish that resembles a small grand
canyon. Aluminum will stick in the flutes of the fine burrs but that
can be remedied with a stick of beeswax kept handy. Just touch a warm
burr to it every so often and the metal just flys off. WD-40 also works
(perhaps the ONLY good use for this stuff?) though it is more expensive.