things that get in the way of a port and polish job

[amalventano1@comcast.net (Allyn)]

Rob,
    You will need to read what i have pasted here. Its a post from sh=
awn a while back. Definite
important info for you to do your work effectively.

---------------------
I got this from Underhood Service, November 2001. Pretty cool and
explains alot of stuff for all you youngins. The Science of Horsepowe=
r:
Porting & Matching Heads & Manifolds, Larry Carley.


Air flow makes horsepower. The more cubic feet per minute (cfm) of ai=
r
that flows through the intake ports and into the combustion chambers,
the more horsepower the engine makes.

A larger carburetor or throttle body, bigger valves, a high-lift,
long-duration camshaft, three-angle valve job and exhaust headers are
all performance enhancements that increase air flow for more power. A=
dd
a turbocharger or supercharger and even more air is forced through th=
e
engine. But bolt-ons can accomplish only so much. To realize the utmo=
st
performance potential from a given combination of cubic inches and
mechanical modifications, you also have to optimize the ports in the
cylinder heads and match the ports to the runners in the intake
manifold.

There are two ways to port and match cylinder heads: The right way an=
d
the wrong way. The right way is to refine the flow characteristics of
the head and manifold so as much air as possible enters the cylinders=
 at
the engine's peak power curve. Every engine is different so there's n=
o
"standard" port configuration that is guaranteed to deliver maximum a=
ir
flow on every application. The port profile that works best will be
limited by the physical dimensions of the cylinder head.

Limiting factors include the size, position and angle of the stock
ports; the size, configuration and angle of the valves; the thickness=
 of
the casting around the ports; and the location of the water jackets,
head bolts and other valvetrain components. But other factors must be
taken into account, too, such as engine displacement (big block versu=
s
small block), the engine's bore and stroke, the shape of the combusti=
on
chambers, compression ratio, the depth and angles on the valve seats,
total valve lift, camshaft profile (duration, overlap, etc.), and typ=
e
of intake manifold and induction system.

Porting can unleash hidden horsepower by increasing air flow - but it
requires know-how, a flow bench and special tools to successfully pul=
l
it off.


Opening Up:
One of the basic goals of head porting is to minimize obstructions so
air can flow relatively unimpeded from the throttle plate to the valv=
es.
Two things that get in the way are the valve guides and valve guide
bosses. Cutting down the length of the valve guide stem and narrowing
the valve guide boss can improve air flow past these obstacles. So to=
o
can using smaller diameter valve stems or valves that are necked down
just above the valve head.

Bolt bosses that protrude into ports also create bumps in the ports t=
hat
disrupt air flow. Grinding these flush with the surrounding port surf=
ace
can also smooth out the route, provided you don't run out of metal an=
d
grind all the way through the boss or dangerously weaken the head.

Transition areas in the port also need to be reworked so air will flo=
w
more easily around corners with a sharp radius and into the seat thro=
at
just above the valves. Sharp edges and rough castings also need to be
smoothed and blended to eliminate turbulence and improve air flow.

The cross-sectional area of most intake ports becomes gradually small=
er
as the air moves toward the valve. This causes the air to accelerate =
as
it approaches the valve, and actually helps ram more air past the val=
ve
into the cylinder when the valve opens. Any sudden changes in the
cross-section of the port can disrupt this effect and restrict air fl=
ow.
That's why port modifications that are made in the area just above th=
e
valve must not upset the normal increase in air velocity. The same go=
es
for the exhaust side, too, except here the cross-section of the ports
gets larger as the exhaust gases flow away from the valves. Again, th=
e
secret to maximizing flow is to have a smooth transition and as few
obstructions as possible.

The joint where the intake manifold and cylinder head meet also is a
critical area. If the runners in the intake manifold are not perfectl=
y
aligned with the ports in the head, sharp edges can interrupt normal =
air
flow and impair performance. Matching up the ports so there's a smoot=
h
transition from manifold to head will ensure maximum air flow. The sa=
me
goes for exhaust ports. The head ports must be aligned with the heade=
r
openings so the exhaust gases can pass freely out of the engine witho=
ut
encountering any sharp edges or obstacles.

The right way to improve air flow is to locate the best places to rem=
ove
metal (or in some cases, to even add metal). This takes experience
(knowing what kind of changes work and what ones don't), using the ri=
ght
tools (properly shaped cutters for reworking the various portions of =
the
ports, valve pockets and manifold), and a flow bench to measure the
changes in air flow produced by the various changes that have been ma=
de.

The wrong way to go at it is to grab a die grinder and start hogging =
out
the intake and exhaust ports with no idea of where you're going or wh=
at
you're trying to accomplish other than to open up the ports.

Bigger is not always better. Grind away too much metal and you may en=
d
up ruining the casting if you cut into a water jacket. But even if yo=
u
don't grind all the way through, removing metal in the wrong places c=
an
actually end up hurting air flow more than it helps. Here's why: The
secret to maximizing air flow and engine performance is maximizing
volumetric efficiency and air flow velocity.

Big ports with lots of volume will obviously flow more air than a
smaller port with less volume - but only at higher rpm. A lot of peop=
le
don't know that. At lower rpm and mid-range, a smaller port actually
flows more efficiently and delivers better torque and performance
because the air moves through the port at higher speed. This helps pu=
sh
more air and fuel into the cylinder every time the valve opens. At
higher rpm, the momentum of the air helps ram in more air, so a large=
r
port can flow more air when the engine needs it.

The ultimate port would actually be one with a variable cross-section
that's small at low rpm for high air flow velocity and gradually open=
s
up for more air flow as engine speed increases. That's sort of the id=
ea
behind staged split-plenum intake manifolds that open up and feed mor=
e
air into the engine at higher rpm.

The bottom line is this: To realize the most power and performance ou=
t
of an engine, air flow has to match the breathing requirements of the
engine within the engine's rpm range where it is designed to make the
most power.

A set of killer aftermarket heads with huge ports and valves that are
engineered to flow more than 500 cfm with a 0.800" valve lift at 8,00=
0
rpm may be the hot setup for a 585-cubic-inch Pro Stock engine, but
would be overkill on a street-driven, big-block Chevy that has a less
radical cam, gearing and a redline of only 5,500 rpm. That's why
big-block Chevy heads with smaller oval ports work better on the stre=
et,
and big-block heads with larger rectangular ports perform better on t=
he
strip.

Therefore, when choosing either an OEM cylinder head or an aftermarke=
t
head, you should try to match the port size with the engine's power
curve and rpm range. Don't waste your money bolting a set of high-flo=
w
heads onto an engine that can never realize the head's full performan=
ce
potential because of limitations in gearing, the valvetrain, cam
specifications or carburetion. Likewise, if you're going all out, the=
n
start with the highest flowing heads you can find and try to add even
more cfm potential by massaging the ports and manifold.

Kevin Self of Self Racing Heads & Engines, Durant, OK, said CNC
(computer numeric controlled) machined aftermarket heads are a great
place to start because the port configurations are based on designs t=
hat
have already been proven to deliver maximum air flow. Even so, there'=
s
always some room for improvement. Self said he can usually find an
additional 25 to 30 cfm improvement in air flow in many CNC heads by
tweaking the head on a flow bench.

"One of the advantages of CNC heads is that they all have very
consistent flow characteristics. But, because they're all the same, y=
ou
don't necessarily gain any advantage over a competitor if he buys the
exact same set of heads as you. If you can't improve the head, you'll
have to find more horsepower someplace else, otherwise you're not goi=
ng
to go any faster than the next guy."

CNC machining is much faster than hand grinding, and produces ports t=
hat
have uniform profiles. But someone still has to develop the initial
profile by hand and then prove it works on a dyno and on the track.

As for port alignment, Self said the runners in the intake manifold
should be about .050" smaller than the port opening in the cylinder h=
ead
to allow for any misalignment that occurs during engine assembly.

"We've developed a special 'Port Intruder' kit that allows you to nar=
row
the thickness of the wall between the intake ports on small-block Che=
vy
heads without increasing the risk of cracking the manifold or deck ar=
ea
of the head. The kit allows the use of a shorter head bolt between th=
e
ports, eliminating the need for a head bolt or bolt sleeve between th=
e
ports. The head must be machined to accept the Port Intruder plugs. T=
his
change alone can increase air flow up to 30 cfm," said Self.

Bob Irvin of M2 Race Systems, Farmingdale, NJ, said his company
specializes in CNC-machined cylinder heads. "We use outsiders to deve=
lop
the port configurations, then digitize the ports for reproduction on
customers' cylinder heads."

Irvin said he charges a one-time fee of $2,000 to digitize and progra=
m a
port configuration, and $1,200 to $1,500 to CNC machine a pair of
cylinder heads (which includes valve seat and guide work, too).

"CNC is foolproof and is much faster than trying to port a set of hea=
ds
by hand from scratch. But there's no reason why you can't do addition=
al
finishing on the heads after they've been CNC machined to find some
extra power," said Irvin.

Where It Counts:
As a rule, the roof of an intake or exhaust port has much more influe=
nce
on air flow than the floor or sides of the port. The greatest gains i=
n
air flow can often be realized by removing metal from the top of the
port only and leaving the sides and floor relatively untouched. This =
can
have the same effect as using a different head casting or an aftermar=
ket
head that has the ports relocated slightly higher to give a straighte=
r
shot at the valves.

Additional gains in air flow can often be found by carefully smoothin=
g
and blending the short-side radius in the port floor where the port
bends toward the valve seat. This helps air round the corner more eas=
ily
for improved air flow.

In the area where the intake manifold and head are bolted together,
using a template to scribe alignment marks on the head and manifold c=
an
serve as a guide for hand grinding and smoothing this area.

Mr. Gasket Company's plastic "UltraSeal Port Gauge" templates for
small-block and big-block Chevys can be used for this purpose, and ar=
e
much more accurate than using a gasket as a template.

Expert Advice:
Joe Mondello, who's name has long been synonymous with high-performan=
ce
cylinder heads, said a lot of people who don't really know what they'=
re
doing jump into head porting and make big mistakes.

"They take out metal where they shouldn't be taking out metal and end=
 up
with ports that are too big and don't flow as well as they should. Th=
e
shape of the port is far more critical than the overall size of the
port," stated Mondello.

Mondello, who teaches the secrets of building, porting and flow testi=
ng
high-performance cylinder heads at his Mondello Technical School in P=
aso
Robles, CA, said he also sells special porting tools that are designe=
d
for every part of the cylinder head.

"When you're doing the short-side radius of a port, you don't want to
take out too much metal. You just want it to be nice and smooth,"
instructed Mondello. "Trying to get around the short-side radius bend=
 is
difficult unless you use a cutter that's designed for that purpose.

"When cleaning up the bowl area, blending alone won't improve flow
unless you also remove some metal to increase volume. Many people don=
't
do valve bowls properly. You have to blend everything from the base o=
f
the valve guide to the base of the primary valve seat, and then do a
3-angle valve job. Otherwise you're just scratching the valve bowl an=
d
ports, and aren't really gaining anything."

As for matching ports, Mondello said not to use gaskets as a guide
because there's too much variation in gaskets and most aftermarket
gaskets have openings that are up to 1/8" larger than the port runner=
s.
If the port is enlarged to match the gasket, it can reduce air veloci=
ty
and hurt performance.

"We teach port matching, not gasket matching. I pick the largest port=
,
match all the others to it, then do all the work inside the port to
maximize air flow around the pushtube turn because that's where the
biggest restriction is in the port," said Mondello.

"The largest gains in horsepower are found on the intake side by rais=
ing
the roof of the port (the side closest to the valve cover) by .100" t=
o
=2E175". The amount of metal in the top of the intake manifold runner=
 will
determine how high you can raise the roof.

"On late-model Chevy Vortec heads, you don't want to change the shape=
 of
the port much. The best advice here is to clean up and equalize the
ports so they have the same height and width. On small-block heads,
there's a large pocket right below the rocker arm stud in the roof of
the port. This should be filled in with epoxy to improve air flow. Do=
ing
that will give you an extra 15 cfm.

"On exhaust ports, if you tried to match the port to a header gasket
you'd probably destroy the port. The secret of exhaust porting today =
is
not how big the port is, but the shape of the port and the velocity o=
f
the exhaust flowing through it. We don't even flow test exhaust ports
anymore because most heads have plenty of flow capacity as is. All we
care about is velocity and pressure.

"Nearly every single exhaust port today, except for Ford 302, 5.0L an=
d
351 heads, are big enough. The only thing we do to enhance air flow i=
s
raise the roof of the port about 0.100", depending on the headers use=
d.
We don't touch the floor of the exhaust port or the sides unless we h=
ave
to get rid of a hook, seam or rough area in the casting," said Mondel=
lo.
"Any time you start making the ports bigger on the exhaust side, you
usually end up killing air flow in the head. I'm talking a reduction =
of
25 to 30 cfm. All you need to do is clean up the valve bowl, blend th=
e
short-side radius, and raise the roof slightly. Don't touch the floor=
 or
walls."

Mondello explained that CNC machining and hand grinding are two
different techniques for porting heads. "Everybody says CNC is the wa=
y
to go. But you first need someone who can take a raw casting and rewo=
rk
it so it has good air velocity and flows well. Then you can digitize =
it
and reproduce it with CNC tooling on other heads. There are a lot of =
CNC
profiles being sold today, but I think most have some room for
improvement. Additional hand grinding can usually pick up another 10 =
to
12 or more cfm."

As for polishing, Mondello said a smooth finish is great for exhaust
ports, but a rougher finish flows better on the intake side. He
recommends using 300- or 400-grit paper followed by a Cross Buff for
polishing exhaust ports, and 50- or 60-grit paper for the intake port=
s.
A slightly rough surface texture in the intake ports and intake manif=
old
runners creates a boundary layer of air that keeps the rest of the ai=
r
column flowing smoothly and quickly through the port.
DIY Porting:
Though the greatest gains in horsepower will be realized only when he=
ads
are flow tested and professionally ported, do-it-yourselfers who are
racing on a limited budget can still do some basic porting themselves=
 to
improve air flow and increase the performance potential of their
engines.

The technical staff at Standard Abrasives (www.sa-motorsports.com) ha=
ve
an online DIY Cylinder Head Porting Guide complete with photos that
provides detailed step-by-step instructions for head porting and
manifold matching.

All you need are a basic porting kit (which includes various grinding
stones and abrasive rolls), some common tools and some free time
(typically 10 to 12 hours to port a pair of V8 heads).

A basic DIY port job should focus on reducing restrictions caused by
steps that may obstruct intake air flow as it transitions from the
intake manifold to a smaller intake port entry in the head. These
restrictions could be casting bumps, ridges or other marks, such as
those on port floors or roofs, sharp edges, such as those around the
valve guide bosses at the top of the valve pockets, and the area wher=
e
the intake port floor curves down to the valve seat.

The job itself consists of six steps:

1. Enlarging and matching the intake port entrances;

2. Smoothing the intake short-side radii, valve guides and valve
pockets;

3. Smoothing the exhaust short-side radii, valve guides and bowls;

4. Polishing the exhaust ports and bowls;

5. Polishing the combustion chambers (to reduce carbon buildup); and

6. Matching the intake manifold ports to the head.

Some porting suggestions offered by Standard Abrasives include:

=2E Use an air-powered die grinder with a maximum speed of 18,000 to
20,000 rpm and a 1/4" collet. An electric die grinder is OK, but you
have to be careful to limit the grinder's speed.

=2E Wear proper eye protection. Grinding throws off a lot of chips, a=
nd
you don't want any debris to end up in your eyes. Good lighting is al=
so
essential so you can see what you're doing, and gloves are recommende=
d
to protect your hands.

=2E To keep grinding stones from clogging when working on aluminum he=
ads,
lubricate the stones with WD-40.

=2E To figure out how much metal needs to be removed to match up the
ports, apply machinists bluing to the gasket template and bolt the
template to the head and manifold. Then scribe the outline of the por=
t
opening on both the head and manifold. Remove all metal inside the
scribed lines.

=2E When you start grinding, use a rotary round grinding stone for ma=
ximum
metal removal. As you approach the scribe marks you've made, blend or
feather the larger port into the remaining port by progressively
removing less material as you move farther down into the port. In mos=
t
cases, you want to grind about 1" to 1.5" into the port.

=2E Once the port has been ground to size, switch to a smaller diamet=
er
conical rotary stone to profile the small radii at the corners of eac=
h
port.

=2E To finish the port, use the tapered rolls of abrasive, starting w=
ith
40 grit, then 80 grit.

=2E The point where the intake port floor curves down to the valve se=
at is
known as the "short-side radius." From an air flow standpoint, this a=
rea
is the most critical in any port. Smooth that spot and you can usuall=
y
realize a significant increase in flow through the port. On most
production heads, the short-side radius will be sharp-edged and rough=
.
The goal here is to soften those sharp edges and smooth out the
roughness.

=2E Bowl work includes blending the area under the valve seat. The va=
lve
throat, which is the smallest diameter in the valve pocket just above
the valve seat, should be about 85% of the valve diameter. If the thr=
oat
is smaller than that, use a combination of the rotary stone and
cartridge rolls to open it up to the 85% figure.

=2E Exhaust ports flow best with a polished finish. A smooth finish a=
lso
helps reduce the buildup of carbon deposits. Use a 120-grit or finer
flap wheel after using the 40-grit and 80-grit abrasives, then polish
with the medium Cross Buff and finally the fine grade Cross Buff.

=2E In most cases, you should not attempt to match the exhaust ports =
in
the head with the ports in the exhaust manifold or headers. Many stoc=
k
exhaust manifolds, and virtually all tube headers, have larger port
sizes than the heads. You want that "step" from the port to the large=
r
header tube or exhaust manifold because, as pressure pulses flow back
and forth in the exhaust system, it acts as a "reversion dam" by
resisting back flow of exhaust gases into the port.

Good shit eh!


Shawn M=E9ze

--------------------------------

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original cl=
utch, driveshafts, wheels :)

----- Original Message -----
=46rom: Rob Cotner
To: scirocco-l@scirocco.org
Sent: Saturday, February 16, 2002 9:02 PM
Subject: things that get in the way of a port and polish job


This is all on an '84 JH 8v- I am trying to port and polish my head(w=
ith a dremel.... this is gonna
take awhile)  and the plastic things that surround the fuel injectors=
 are making it a real bi%ch, if
not impossible to polish much of the intake.  Is there any way to rem=
ove them and put them back in?
The injectors are out, I just am hoping to rid of their plastic surro=
unds.  The valve guides are
also getting in the way, but unless anybody has a brilliant solution =
other than pressing them out I
might as well not even ask...
Lastly, to anyone else that has done a port job have you noticed that=
 you can't widen up the intake
much beyond stock because of the gasket?  Is there anyway to widen th=
e new intake gasket? The
exhaust ports can be increased by what appears to be a good 40-50%, b=
ut the intake is ofcourse
another story.
Thanks alot,
Rob







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