~FLATHEADS~
1. OVERVIEW & HISTORY                7. IGNITION
2. FUEL FLOW                                8. INDUCTION
3. HEADS                                       9. EXHAUST
4. CAMSHAFTS                             10. LUBRICATION    
5.
CRANKSHAFT
6. RODS & PISTONS
HEADS  
The heads of a flathead engine have always been a subject of great
interest, and debate. They cover the valve and create a ‘pocket’ over the
valve where the fuel mixture enters into a transfer area and then into
the combustion chamber. As related in Fuel Flow, a stock head from
Ford has a generous transfer area which worked well in normal
commuter usage. Stock heads were also used by many a racer with
success; in fact many tracks had rules in place that allowed only stock
heads. Now, racers being racers, and looking for any advantage, could
often find their way around such rules and many did. The aluminum
Canadian head was often used (in contradiction to the rules of some
particular tracks) in lieu of its cast iron brother by many racers and
then covered with paint. Racers also would weld up these Canadian
heads in the transfer area and re-machine them to get greater
compression (this was also often done by brazing on the cast iron
heads). Or if they had the cash then they could just buy a pair of
Weiand ‘cheater’ heads which looked exactly like the Canadian
externally, but were decidedly different under the gasket. Some guys
pushed it even further and just bought the finned heads and then
milled off the fins (‘Mad’ Marv Shaber comes to mind), especially if the
rules related ‘no finned heads.’ So why go to all this trouble when the
stock cast iron heads were so plentiful, cheap, and worked well?
There are several advantages to the aluminum head on a Flathead. One
is weight of course, another is cooling ability, but the most important
for a racer is the increased compression an aluminum racing head
offered. This was achieved by reducing the volume of the transfer area
and also creating a ‘squish’ combustion chamber in which the outer
edges of the chamber are in closer proximity to the piston than in the
center of the chamber which forces the mixture back towards the spark
plug location. So, we slap a set on and we’ve got more compression,
better capacity for cooling and one of the main reasons that most guys
were drawn to the heads in the first place – they just plain look cool.
There’s nothing prettier than a set of finned heads on a flathead.
OK, so let’s start with the stock heads. I talked with Sammy Reakes
once who related that they had a set of racing heads in place on one of
his earlier 248 cu. in. engines (probably a John Davis #17) and one of
them cracked. They replaced the heads with a set of cast iron truck
heads and he said the engine immediately ran better. I’ll make the
assumption that Sammy’s stock heads flowed better than the racing
heads they were using. The stock cast iron head had some advantages;
One, it was cast iron so it would expand at the same rate as the block
providing a better seal; Two, it was more rigid and less susceptible to
warping; Three, it had a much deeper transfer area which allowed
better breathing. Due to this larger transfer area though, the
compression was lower. The Canadian head was of the same basic
configuration but made of Aluminum which transferred heat better but
was more likely to warp. Now, once these heads were modified by
welding to increase the compression, (by filling in the transfer area);
the racer now had to relieve the block in order to get his flow. I have a
set of Canadian heads that Bob Hayslett modified and related to me
that ‘you can’t squeeze a popcorn fart into them’ meaning they didn’t
flow well and hence didn’t work too great. We tried them and found
this to be true. With a flathead you have to Rob Peter to Pay Paul, you’
re either going to get compression or flow by messing with the transfer
area. Flatheads don’t have a tremendous amount of compression in the
first place and no racing engine will run worth its salt without good fuel
flow, especially as high RPM’s so my conclusion is that it’s more
important to get the flow. There are other ways to get that compression
up which we’ll explore later but first let’s get the fuel in there.
As with any assembly, the sum of anything successful is always greater
than its parts. Every component has to work in concert with one
another. We have the block ported and relieved at this point and let’s
imagine you’re a fuel molecule heading down the port, the valve opens
and you make your first right hand turn upward towards the valve.
Once you get there where do you want to go? As with anything that
has mass, you want to keep heading in the direction you started. Bang!
You’re into the head and hit a wall before getting sucked down into the
cylinder. How can we make this a more enjoyable journey for you?
Now, I’m not saying that the high compression head doesn’t work or
flow well, that’s just not true. Many a racer won with Offenhauser,
Edelbrock and Edmunds heads in our area with no modifications made
to them. What I am saying is that with a few modifications, they can be
considerably better. I don’t have any flow chart data nor do I have a
dyno. What I can relate is based on my own ‘seat of that pants’
experience on the track and after I made a few modifications to some
Edelbrock heads, the engines ran better – with everything else equal as
I tried different heads on the same engine. Cut and try.
The high compression head in general squeezes the mixture down in
the transfer area, just as the fuel is heading upward so it stands to
reason that since you relieved the block in this area, maybe doing the
same to the head will do some good. Barney Navarro has been building
and playing with Flatheads since the 40’s and his latest heads have
this relief over the intake valve into the transfer area (which is still
filled in) then onto the combustion chamber. His theory and flow
testing showed that once the fuel mixture left the port, it wanted to go
upward. Many others have related in their books and such that this
proves that relieving a block is of no use but I disagree as far as racing
goes. At higher RPM’s where the mixture is moving so rapidly, any bit
of flow helps and all my relieved engines have run better than non-
relieved ones. Following up on what Barney’s testing found,
development of the Flathead V8 racing head basically ended in the
1950’s when the OHV’s took over the racing scene but in motorcycle
racing it was different. The AMA (American Motorcycle Association) that
governed the flat-track racing world allowed an advantage to the
flathead powered machines in cubic inches so many Harley Davidson
riders took advantage and developed the flathead porting further. They
found by opening up the valve pocket over the valve that significant
gains could be had in performance. They also did a great deal of work
around the valve guide in making the transition smoother, all this
netted more flow.  Another manufacturer of note in this area is Kohler
who developed a nice smooth transfer area (which is very similar to Earl
Evans).  If you look at today’s offerings from Barron you’ll notice the
similarities. I tried Barney’s theory out on a set of Edelbrocks. We
welded up the valve pockets and then ball milled a generous radius in
the corners around the intake valve, made the pocket over the valve
and then extended this depth to the transfer area. I did a lot of
polishing and the end result was that the heads worked very well,
much better than a ‘stock’ set.  I know of several racers who set their
valve pockets up with minimal clearance, some very successful ones
have told me that they like to see the valve impression on the head. I
think that’s too tight so here’s how I do it. With the cam and valve
assembly in place, put the head on the block without a gasket and turn
it over. The head should not lift off the block (I put some silly putty in
the pocket to check and see what I really have), a Victor sandwich
gasket compressed is 0.050 and that’s where I set my clearance. Many
say to set at 0.040 minimum and that’s probably plenty as we’re using
good Zephyr springs anyway so those valves aren’t going to float. The
thought here is that the fuel mixture doesn’t just leave the pocket and
go directly across the transfer area and down into the cylinder, it flows
all around the valve and over it as well so anything you can do to open
up this area is beneficial to performance.
OK, so aside from going to all the bother of welding up your nice
aluminum finned heads and then having them re-machined while you
sweat what else can you do to improve their flow? An easier
modification includes a die grinder, a steel template, and a rounded
carbide burr. Again, in one of my conversations with Bob Hayslett we
were talking of getting the heads to flow better and he related a
suggestion that Bobby Meeks had made to him some 40 years ago.
Meeks was Vic Edelbrock’s right hand man and built all of his racing
flatheads, so he really knew what he was talking about, just like
Barney Navarro. He related to Bob that if he really wanted to improve
performance, he needed to open up the valve pocket by undercutting
and radiusing around the valve into the head. Bob said he was going to
do it but once he got everything in place, he couldn’t bring himself to
put a tool to those beautiful heads. I honored his thought and got
another set to modify instead. I took a head gasket and scribed out the
valve pocket ‘eyebrow’ on a piece of plate steel and then cut it out,
drilled holes to bolt it to the head and used it as a ‘follower’. Then take
a round carbide burr and place it in a die grinder, set the desired
depth and start whittling. The idea is to get some relief around the area
where the valve enters the head and provide a nice radius for increased
flow. It’s really not a new concept, Bill Marsh has related to me that Ed
Winfield was doing this in the 20’s and incorporated this in his
Flathead ‘T’ designed heads, and Ed was a genius who ran like stink. I
only radius around the intake valve and then use some Norton carbide
impregnated polishing wheels to clean it up. Other than that, I break
the edges of the transfer area into the combustion chamber of the head
and make sure there are no sharp edges anywhere, then polish
everything up with scotchbrite. Works really well and anyone can do it.
It’s only fair to note that other manufacturers used a different theory
which was the mirror image of getting more fuel into the engine. They
felt that the Flathead suffered from too much back pressure and
designed their heads accordingly. Kogel ‘Racer Rocket’ and Sharp
heads used a relief on the exhaust side of the valve pockets which is
exactly the opposite of Navarro’s, Winfield’s and Bobby Meek’s theories
of getting more fuel in. Art Christman used Al Sharps heads and won
many drag races as well as setting Bonneville records so we can only
conclude that they worked well. Automotive engineers will tell you that
the exhaust only needs to flow @ 65% of intake, which supports the
theory that intake flow is more important. My personal experience is
that opening up the intake pocket on the flathead increased
performance at the track, getting the exhaust out is important too but I
think it can be taken care of with ample porting in the block, and
contouring the exhaust valve guide accordingly.
Now, hows we gonna get that compression back? There are two ways I
can think of off hand (three if we include the camshaft). One, of course
is by using a stroker crankshaft. The Ford crankshaft, regardless of
year, is 3 & ¾ inch stroke, the Mercury crank was also 3 & ¾ inch
stroke through 1948 but was increased to a 4 inch stroke in 1949. So,
the use of the Mercury crank will immediately give you more
compression with everything else equal. Now, take that Merc. crank
and have it offset ground (to the earlier, smaller 21A or 91A rod throw
dimension) and you can gain an additional 1/8 inch (or more
depending on your pocketbook) stroke increasing compression and
cubic inches even more. This is the best way to obtain compression as
the longer stroke creates more volume in the cylinder which when
compressed creates more compression, the additional cubic inches
help performance as well. We’ll get into that in the crankshaft
discussion. The camshaft option of creating compression would have to
be a camshaft with little overlap (when both valves are open) which isn’t
good for scavenging incoming fuel mixture at high RPM’s so it’s not the
right option, unless of course you’re going to gain your compression by
use of a supercharger. The third way to get the compression up is by
using ‘Pop-Up’ pistons and since many tracks had rules in place
limiting cubic inches (eliminating or greatly restricting the strokers),
many racers used this option. This can be done in a few different ways:
One: Buy ‘HC’ or high crown (high compression) pistons, these pistons
had a greater amount of material above the top compression ring and
as such would ‘pop’ the dome of the piston above the block deck
surface. Two: Use either a Ford piston (3 & ¾ inch stroke) on a late
Mercury crank (4 inch stroke) or if you can use a stroker, then a
Mercury piston (4 inch stroke) on a Stroker crank (4 & 1/8 inch
stroke). The piston wrist pin placement is really the only difference in
these pistons so you’re raising the piston in the bore in each or any
related instances, thus giving you the same effect as the Pop-Up piston.
The only thing you have to watch when you do this of course is where
you’re top ring land ring ends up, with a relieved block you have to
check the piston, with your top ring on to ensure you have ample bore
over the ring at TDC, you don’t want to catch that top ring on the relief,
it’ll break it in an instant, 0.040 should be sufficient safety when
checking this but that’s just a swag. I doubt you would run into trouble
with that much cushion. The last way to get that piston out of the block
is to deck the block surface itself to get your desired pop up. Barney
Navarro’s ‘Hemi’ High Flow heads in conjunction with the
corresponding Arias pistons do this. The combustion chamber is
shaped in a Hemi dome with matching pistons and only the dome of
the piston is exposed beyond the block’s deck. He felt that this
eliminated the problem of end gasses and consequently blown head
gaskets, I’m sure it works very well but the set up is not cheap. The
racers I know of the 50’s and 60’s in general used the ‘LC’ Low Crown
(low compression) pistons and then machined their deck surfaces down
until it was even with the edge of the piston, exposing just the crown as
Navarro’s set up does. Then you can adjust your clearance over the
piston and valves by decking the heads. This takes time, careful
measurement and some $$ at your local machine shop. I’ve only seen
one set of true ‘Pop-Up’ pistons and Bob Hayslett sold them to me.
These put not only the crown of the piston out of the block but also a
good portion of the material over the top ring land, 0.110 if memory
serves me right. This necessitated that we clearance the heads as the
stock Edelbrock chamber wouldn’t accommodate the additional
material. We made up a cutter in which I increased the amount of
‘squish’ in the combustion chamber and then started cutting the layed
out heads (I blued the chambers, bolted them to the block and then
used a machined piston to find each chamber’s exact center, the heads
are placed on dowel pins to repeat the location). The chamber cut
beautifully but once we started to bore into the heads the Bridgeport
started walking across the floor. Back to the drawing board, we made
up a nice plate fixture to hold the heads and then used a P&W 3E Jig
bore to do the job, who says working in the jet engine industry doesn’t
have advantages? I gave the bore in the head 0.010 clearance over the
cylinder bore and used stock Ford (Felpro) head gaskets since the bore
size was only 0.060 over. With the fuel charge wanting to go upward
anyways, I thought this was the way to go and was my attempt to get a
Navarro type set up but then do it myself. The end result was fantastic
compression and the engine ran extremely well although I do think
with some more tweaking it’ll do even better, that’s the plan for the
future. OK, enough on heads, let’s go to
camshafts.   
Non-turbulent (left)
and turbulent head
design.
Cut-away of a
high-compression head.
Stock 8BA
combustion chamber.
Note deep transfer
area.
Nothing prettier than
a 59A Edelbrock
racing head.
Edelbrock chamber.
Offenhauser 8BA
head.
Offenhauser
chamber.
Evan's 59A head.
Evans chamber.
Harley Davidson
combustion chamber,
note relief shown
over intake valve.
Earl Evans chamber.
Modified head,
radiused  and
carved out intake
valve pocket
extended to
transfer area
.
This cutaway
exhibits the flow
around and over the
top of the valve, You
can see where the
radiused pocket
helps.
Porting and radius
tools.
Radius follower tool
in place on head.
Set the carbide burr
at desired depth
and start carving.
Al Sharp's pretty
heads.
Sharp chamber,
note relief over
exhaust valve.
Pop-up Piston set-up.
Modified piston finds
combustion chamber
center for machining
set-up.
Combustion chamber
cutter, we made this
one adjustable with
a 7 inch radius.
Finished head,
welded, radiused,
machined, bored,
and polished, works
pretty darned good.
Additions 4/15/07
This pamphlet advertises the 'Jiggler' head made in the 1940's and 1950's for the Ford
V8 '60' engines and further supports the theory that getting the exhaust out of an 'L'
head configuration is paramount in gaining performance. A neat item, I still wonder how
successful they were with no water jackets (you'll note the 'racing version' was set up
with Methanol). An intermediate step (for the '60's') between the flathead and OHV
conversions such as produced by Ardun, Stevens, Riley and others; it wasn't cheap and
I've yet to see one in the flesh. Does show the extent that racers would go to in trying to
beat the Offies in a midget. Published in 1953.