Philosophy of Building
a Nostalgia Fuel Motor
By Jim Burke
Jim Burke served as crewchief on John Lukens TAFC. Photo courtesy of Jim Burke
The philosophy is simple: use only the parts necessary to get the job
done and spend your money on certain areas where it will be very
beneficial. Do not try to build a Pro motor; i.e., dual pump, dual mag, or
the latest and greatest trick of the week part. Establish the building in
sequence, achieving each goal as you go.
Since you will require this motor to be able to perform well and
reliably, you must set achievable goals. The first is power. At worst case
to be able to pull a 4 disc direct drive, the motor has to be able to put
out about 2500 to 3000 hp. Now that we have our power levels set, the
method to develop this power and keep it in one piece is the next goal.
Here comes the tricky part because drag racers have been brought up on
more is better and if the pros do it, it has to be right. Well in this
case it is actually all wrong. If you try to build a motor like that you
will blow it up or burn it down. Either way it is not a pretty sight --
about the same as burning a fistful of one hundred-dollar bills.
The Nostalgia Nitro motor should be run at about 6500 rpm. Yes this is
fairly close to a good running Alcohol motor and the truth is the
nostalgia motor is actually a hybrid running between the two styles of
motors. You need to run the motor at that speed to be "on" the
fuel pump or close to its max capacity.
Since we are talking about a Nitro motor here, the first question is,
"How much of a load is it running?" Or in English, what
percentage of Nitro are you running. Actually, NHRA/IHRA had it right as
you can run 90% without hurting anything. Having said that, I recommend
that you start with about 85% and sort out your engine combination first
as a few percentage points of Nitro make a major difference.
Since we are going to start with 85%, then the rest of the power has to
come from somewhere. The first place most people think about is the
blower. You know, turn up the boost and make a lot of power. Well that is
true but this really places a large load on the motor and stresses the
motor parts in all the wrong ways. Actually, the best way is to increase
compression. There is more to this than just raising compression. You need
to remember that this is a motor combination where all parts work
together. The amount I am talking about is raising the compression from
the 6:1 that is normal for a Nitro motor to about 7.5:1. Not that much,
but with Nitro it makes all the difference in the world.
So now we have a Nitro motor on 85% Nitro and 7.5 compression. Sounds
more like it might be an injected motor and that is exactly what you are
building but with a blower. This lets the motor do the work. The final
touch is to add a blower that puts out about 25 pounds of boost and you
have a recipe for large horsepower and small wear and tear.
Since we have established the basic parts of the motor, it is now time
to turn our attention to the fuel system. My basic philosophy is that you
can never have too much fuel pump. There are many reasons for this.
Let's start with what is called backsiding a piston, or visually,
burning down one side of the piston. Most people believe that you burn up
pistons at the top end. This is not right; it is really the result not the
cause. The cause starts the moment you swap feet at the starting line. If
air gets to the piston before the fuel, even for 1/10th of a
second, it will create a hot spot. Remember the basic rule of Nitro: a hot
cylinder that has more fuel added to it does not get cooler but the fuel
feeds the heat and becomes a blast furnace or cutting torch. This also
applies to hot spots on pistons.
So, the lesson here is to have the fuel there before the air at all
costs. Well that might be a slight exaggeration because to do it properly
really doesn't take a lot of money at all but does require that you think.
When you buy your Nitro barrel valve, be sure to tell them what pump you
are going to use so it can be matched up properly.
Most people feel that you really don't need a pump larger than 20 GPM
[Gallons Per Minute]. I am a strong proponent of using a -5 pump that puts
out 28 GPM. The reason for this is split into two parts. The first is
volume.
If you use a 20-GPM pump then you have to remember that this pump is
measured at 4000 rpm at the cam or 8000 rpm at the crank. Since we are
only going to turn 6500 or so rpm then the 20 GPM is not that but
somewhere on the order of about 15 GPM. Now consider what would happen if
you got into a bog situation, which is high load and low rpm. Low rpm
means low fuel delivery and running lean. Sounds like a good way to get
into detonation, which is absolutely the number one killer of Nitro
motors.
The second part of this is fuel pressure. I believe in having high fuel
pressures and this is the most important reason. Just so you understand,
we are talking about fuel pressures at idle of about 150 pounds on the
high side of the system. This high pressure means that when the throttle
is cracked the slightest amount, the fuel will shoot under high pressure
into the injectors and be there before the air reaches the cylinder. If
you can accomplish that then life will be good.
Speaking of air to the cylinders, here is the philosophy for the
supercharger. Most people try to use a 14-71 blower, or if they are being
close to period correct, they will use an 8-71 or a 6-71 blower. Actually,
it is my recommendation that you use a Hi-Helix 6-71 supercharger. The
cost is no different than a regular 14-71 but it gives you a major
advantage in making useable horsepower. Because the Hi-Helix is so
efficient, the air coming out of it is many degrees cooler, which severely
reduces the chances for detonation. One more point: you don't need
anything greater than a bug catcher for a scoop.
Camshafts are interesting in that racers have a tendency to put in the
biggest they can find. When building a Nostalgia Nitro motor the opposite
is true. You use a basic and fairly mid camshaft. The duration should be
about 295 degrees and the lift about .650 inches. This style of camshaft
is available from most Cam manufacturers and does not require expensive
valve springs. In fact, a good source for valve springs is to go to the
Pros and get their "used" springs.
Most people think that since the Pros use the 44-amp mag it is
necessary to run one to make power. Nothing is further from the truth.
These Super Mags at 44 amps require a control box which costs about $2500.
What you really need is a Super Mag V and a matching coil. This does the
job nicely and doesn't cost a lot.
Since we have all this air and fuel and spark, it is best to surround
it with billet cylinder heads. Single spark plug heads are fine but are
now getting harder to find. So find a decent pair of dual plug heads and
simply plug off one set of spark plug holes. Remember that you are running
about half of everything (air, spark, fuel) that the Pros are using so any
dual plug head and manifold you use will work fine. Always try to buy your
heads and manifold as a set when you can, as it will save you headaches
later.
Finally, we come full circle back to the short block. Figure on running
under 500 cubic inches as you don't need more cubes and you definitely
don't need the expense. Use a 5/8 stroker crank and 4.250 bore cylinders.
This has many advantages, but two are the most important. First, the
longer stroke helps with torque so you don't have to push the motor so
hard. Second, by using the 4.250 bore you can buy used cylinders from the
Pros. The Pros use 4.185 bore cylinders and these can be bored out to
4.250. You will have like-new sleeves for about half the cost. An
additional bonus is that with the smaller bore you will have stronger
sleeve walls.
Jim Burke
Nostalgia Funny Car Reunion
www.nostalgiafunnycars.com
jim@nostalgiafunnycars.com
