1. OVERVIEW & HISTORY                7. IGNITION
2. FUEL FLOW                                8. INDUCTION
3. HEADS                                       9. EXHAUST
4. CAMSHAFTS                             10. LUBRICATION     
It only stands to reason that
in order to get a good, clean
charge of fuel air mixture into
your engine, you have to be
able to get the spent charge
out. Working to improve the
exhaust of a flathead is
paramount to better
performance of the engine for
many reasons. First of all of
course is the fact that the Ford
Flathead V8 was designed with
only three exhaust passages
for each bank of four
cylinders. While this design
arrangement gives the
Flathead it’s signature staccato
sound, it also restricts the
exhaust in that the center two
cylinders share an exhaust
port, which isn’t paramount to
high performance flow.
Secondly, the passages snake
through the block in a long
path before exiting, this path
follows alongside the cylinder
bores and water passages
giving the Flathead it’s well
earned reputation as a water
boiler. Anything that you can
do to improve upon this stock
configuration will certainly
improve performance.
You’ll read in engineering
manuals on combustion
engines that an efficient
engines’ exhaust only needs to
flow approximately 65-75% of
what it flows on intake. You’re
already down one port on
exhaust so what did the racers
do? For starters – they ported
– a lot. Cliff Kotary has related
to me on several occasions that
he felt getting the exhaust out
of the Flathead was as
important, or more important
than getting the intake in. The
two have to work hand in
hand. Obviously many speed
equipment manufacturers
agreed (as we have discussed
in both heads and camshafts);
Camsahft grinder John
Schooler’s best cams had more
lift on exhaust than intake
and any owner of a pair of Al
Sharp’s heads can concur that
the valve pockets have more
relief over the exhaust vlaves
that the intake. Their ideas
were that by flowing more on
exhaust, they were creating a
scavenging effect, using the
exhaust to help pull in more
intake charge. No doubt they
both worked, Cliff and other
won a lot of races with
Schooler cams and Art
Chrisman certainly did well at
the drags and dry lakes with
Sharp heads. Barney Navarro
noted also that Ford could
have improved the design
significantly had they run the
exhaust out the top of the
block like Cadillac did, and a
few have done this in recent
history, most notably Dick
Landy’s ‘Flatbotomy’ project
and the late Kong Jackson.
They both added welded ports
to the top of the block which
eliminated the long path and
heating problems – but then
again, I doubt they sounded
like a traditional flathead.
Still, an excellent idea for the
performance minded who has
the ability, or can afford it.
Most of us ‘regular’ guys with
a carbide cutter and
compressor can’t afford it so
the next best thing is to go to
work on the ports. For starters,
at the end ports on each side
of the block there is usually a
big lug of casting that has to
come out and then the port
itself has to be opened up
towards each end of the block.
If you’re really handy then
possibly you can even cut it
out and fabricate a flange to
weld in place like Ron
Halloran did, or if your block is
for drag racing and to be filled,
then you can add ports to the
outside of the block a la John
Bradley. I get them as big as I
can and still take on a header
and do my best to match up
the surfaces. Nice to have the
header flange bolted to the
port to do the grinding – then
fabricate the header later.
Center ports are the same, get
them as hogged out as you
can, you’ll need a long shank
cutter to do this, it isn’t hard –
just time consuming.
At the top of the ports (you
need to be careful you aren’t
getting into the seats when
grinding) – you want to take as
much of the valve guide boss
down as possible and open up
the ports in a ‘D’ shape.
Getting down into the ports is
difficult at first but as you
create more space, it becomes
easier. I polish them up nice
as well. Once I’m done I grind
the exhaust seats at 45
degrees and the valves
themselves at 44 and lap them
lightly, this gets the seat to
the outer edge of the valve and
also gives a positive seal.
Sounds easy, takes time. In
the heat riser that goes to the
intake, I always place wheat
penny. It has to be a wheat
penny, otherwise the Flathead
will reject it as a greenhorn. I
like the sound this gives and it
supposedly helps deliver a
denser charge to the
combustion chamber. Willy
Wust and Cliff (amongst others
I’m sure) often opened this
passage up and placed
another small ‘header’ on top
of the block (you have to cut
away the intake or mold the
header into it) to create
another path for exhaust flow,
every little bit helps I’m sure
but I didn’t want to cut my
intakes or injectors so I use
the penny, remember, it has
to be a wheat.
Through the years there has
been much discussion about
port dividers for the center
exhaust port. I have an
Offenhauser divider and even
procured some high temp
material (hastalloy, thanks
PW) for this purpose. The Offy
design is rather uh – big. It’s
held in place with a set screw
through the water passage and
in my humble opinion, would
just make a small port smaller.
I’ve never used them. The
thinner material is more
appealing to me however,
fitting them then welding
them in place would be tricky
and risky, I’ve never done that
either. The idea is that by
blocking one passage from the
other, you won’t get a dilution
of your intake charge from the
sent charge making it’s way
out of the adjoining cylinder.
Good thought but I question
just how much it hurts,
especially at really high RPM.
My thought was that I’d rather
risk a little dilution than
either having the bulky divider
come loose on a rough track,
or possibly cracking a block
welding it up. I’ve gotten along
just fine without them. Of
course all of this is moot if you
have  crossfire which changes
the firing order to prevent this
occurrence. Or even better
still, an OHV conversion like
an Ardun (and then we can
forget this whole discussion)
but we’re talking flatheads so,
my opinion – forget the divider.
Onto headers. There are many
good designs available, Belond
made really nice ones with
larger center diameter tubing
than the outer tubes, a
‘blockhugger’ design, these
were some of the most
desirable available and many
(Sanderson) have copied the
design today. They are built a
bit like ramhorns and possibly
offer reasonable scavenging
from one port to another. The
cheaper ‘tube’ type headers
many used are certainly better
than the woefully inadequate
stock manifold although they
aren’t matched by any means
as one is designed to clear a
steering box, much better
than stock though. Fenton’s,
in my opinion, fall along the
same lines. I honestly feel
though, the best headers are
made in the shop. I’ve tried
them with collectors and just
straight zoomies, a discussion
I had one day at Stafford with
a gentleman has always stuck
in my mind. He related that
they made the headers, then
painted them with cheap white
spray paint, and fired up the
engine. Wherever the paint
burned, they cut off the
header, then repeated the
process until it no longer
burned off the paint. Good
idea. What you’re looking for is
the hot spot, that’s where the
gas is expanding the quickest
and will create more
scavenging than any other
spot. I also recall talking with
my Guru Bob Hayslett who left
no stone unturned. He talked
to Harvey J. Crane about
exhaust and Harvey related,
“cut them off at 18 inches and
forget it.” He obviously had
plenty of experience. Another
conversion I had  was with
Triumph motorcycle collector
and racer Don Porter. Don was
a great jet engine engineer I
worked with in Connecticut
and he told me of Triumphs
experiments with exhaust and
that they found by placing the
exhaust exit pipe at the same
height as the valve, it created a
harmonic which helped
scavenging, that’s why you see
motorcycles with high pipes
coming out the back.
OK, lots to think about. Cliff
preferred a collector, as did
many racers, but won as much
with zoomies – me too. The
advantage of a collector may be
improved scavenging but
without a dyno to try it out on,
it’s just conjecture. My dyno
on the track showed no
difference. What I ended up
with was Harvey’s zoomies, 18
inches long, tipped upward to
attempt to approximate the
valve height – they work great,
and sound great too. I used 1
and ¾ tubing for this job and
have never has a problem. I
also go them high temperature
powder coated to help preserve
them and keep them cool. That’
s another thing to consider
when building your engine, is
getting the tops of you pistons
high temperature coated, it’s
keep the heat in the chamber
where you want it, away from
the oil and not only helps
combustion but cooling as well.
What to do – the most
important item here is to
remove as many obstructions
to exhaust flow as you possibly
can, open the ports, build
some good headers, match
them to the block. You can
take satisfaction in the fact
that you really can’t do much
to hurt performance when
opening the exhaust up, you
can only do good.
The Stock Ford Flathead exhaust porst leave much to be desired.
Open up that center exhaust.
The end exhaust too.
Almost anything is better than a stock exhasut manifold from a performance standpoint - they make good door stops though!
John bradley's work on Henry's V8 - need a filled block for this stuff I beleive..
Stock engine cutaway shows the center exhaust port clearly heating up the center cylinders and water.
Get that port D shaped and remove all 'excess' metal.
Dick Landy's work on Ron Main's Bonneville engine..
Cadillac had a better idea when it came to flathead V8 exhaust..
Al Sharps' Heads had more releif over the exhaust valves than the intake.
From Ron Halloran's 'Nostalgia' book - a good idea!
Tube headers are a big improvement over stock manifolds.
A set of these make exhaust problems moot..
Homemade headers with a collector are better yet..
Harvey J. Crane's answer..
Belonds may be the nicest manufactured headers made..
Fenton's are highly sought after as well..
A stock EAC - you can improve upon the exhaust arrangement for a performance application.
Art Chrisman did pretty good with them...
Fish carbs on Ardun heads - both ends covered..