2. FUEL FLOW 8. INDUCTION
3. HEADS 9. EXHAUST
4. CAMSHAFTS 10. LUBRICATION
5. CRANKSHAFT
6. RODS & PISTONS
Steve Martin in his book “Cruel Shoes” – funny book in
which there’s a chapter on “How to be a Millionaire”. Steve
starts out the chapter with the revelation that in order to
be a millionaire, first you have to get a million bucks.
Pretty clever. So you want to build a Flathead V8 race
engine? First, you have to get a usable flathead block and
although it sounds simple, that’s not always the case. So
let’s say you have that good, nearly crack free (most blocks
have cracks in the deck surface between head bolt threads
– ‘stress relief’) block and have it disassembled and
degreased. Where next?
First - fuel flow. Ford designed the engine with a
generous 'transfer area' in their head allowing the fuel air
mixture to exit the port of the intake valve and then make
it's turn down into the combustion chamber. Fuel-air
mixture, like anything that has mass, doesn't generally
like to change direction once it's moving and in the
flathead arrangement it's actually has to make two 90
degree turns prior to entering the combustion chamber.
Now every racer likes a challenge and here's a good one.
Coupled with this problem is the low compression of the
arrangement. That's easy right? Just cut down the area of
the valve pocket and transfer area thus reducing the
volume over the combustion chamber and you have more
compression. Performance head manufacturers of the time
did just this in reducing the transfer area. So now you
have your compression up and have created two more
problems, one - less flow and two - more heat. Make the
heads out of aluminum which will help dissipate the heat
better and that takes care of one problem. Fortunately, the
guys making the aftermarket heads of the time were savvy
and built their heads with greater water capacity as well as
of rugged thickness to combat other issues. Still doesn't
help fuel flow and so here's where the racer had to come to
a compromise between flow and compression. You rob
Peter to pay Paul and 'relieve' the block under the head
transfer area to regain some flow, thus losing some
compression. Not to worry, there’s other ways to get that
back and you have to have flow to make power. You'll also
want to get those ports bigger to increase your flow so grab
your electric drill or die grinder and start lightening that
block, there's plenty of work to do. In talking with Barney
Navarro a few years back, he related that the most
important place to remove material from the intake port
was in the top of the port, or the short runner. I took his
advice and have found he was correct, based on
performance at the track. I now leave the bottom of the port
alone aside from polishing and leave the ‘kickup’ around
the valve stock. After all, this is part of what helps the fuel-
air mixture make one of its turns. Don’t worry about a
matte finish, as described before, the mixture goes through
such a turbulent path that atomizing is no problem, I
polish mine to look like a spoon. As your porting out the
intake runner in the block though, take care as to not go
far and hit the water jacket, this can create some problems
so just take this advice and don’t do it. Treat your exhaust
the same way – think of yourself as an atom trying to get in
or out of the chamber. I put my valve guides in and contour
them to the port, and take out any material that creates an
obstacle to the flow. There’s plenty of material to remove
here, Bob Hayslett once told me he figured he took ten lbs.
out of the block when porting, he may have been
exaggerating but then again, maybe not. OK, so you’re
ported and polished, now how about relief? Several
theories here, new thinking is that the relief does nothing
to increase flow. From my experience, I have to disagree,
my best engines have all been relieved.
To do this first it’s best to have a baseline for where the
top piston ring ends up while the piston is at top dead
center. Assembly and some blueing are required to get this
exact, a good rule of thumb is 0.125 depth for relief, some
do more and some less, again it’s a cut and try issue. Next,
lay a head gasket on the blued deck surface and scribe out
the contours of the chamber on the transfer area to be
removed. The next step is really important – place your
guide in the block and then get an old valve and permatex
it in place. This will protect the valve seat as you start
grinding which is important; in fact, always take care of the
valve seat, a few careless whacks on it can cause you
problems later. Determine if your relief is to be a ‘full’ or
‘half’. A full relief opens the transfer area for both intake
and exhaust while the half only opens the intake. Since
exhaust only needs to flow approximately 65% of intake,
many used the half relief to help maintain compression. I’
ve used both with success. At this point start carefully
removing material from the deck surface in the marked out
transfer area and check your work with either a depth
micrometer or caliper. Smooth out all sharp edges and
polish with tapered roll sandpaper using either a die
grinder or electric drill. Take your time. A good port and
polish job comes from patience, experience and willingness
to take a chance. You can’t win if you don’t play. It’s not a
bad idea to practice your technique a bit though on one of
those junk blocks you found that didn’t make the grade for
your build. Next we go to the head.
Area.
Area.
Port.
Port.
(shaded).
Relief.
Relief.