As your engine starts for the first time – the break-in process begins. For most ABC-type engines it’s the most critical period of
their useful lives … but few operators pay much attention to the details.
In the old days, engine break-in consisted of running the iron or aluminum piston (ringed or lapped) within a steel cylinder-sleeve,
very rich with lots of lube for hours and hours. This was intended to wear-in the engine’s rough spots, reduce friction, and
improve power and longevity. Owners of modern ABC-type engines also demand peak power and longevity. Fortunately, breakin
is an abbreviated process, requiring much less time. Improvements are largely the result of CNC (computer numerical control)
production machinery. These programmed robots make individual engine components that fit together almost perfectly – every
time! This results in very little if any rough spots to smooth out. Despite such accuracy, metal components (primarily the piston
and cylinder-sleeve) require heat-cycling to relieve the internal stresses due to their fabrication. Therefore, heat-cycling (breakin)
can be described as the process of heating and cooling the engine from it’s normal operating temperature (at WOT) to
ambient temperature – time after time – until it holds a peaked setting.
Here’s how to perform the job correctly:
1. Decide on a fuel (nitro and oil content). Your Fantom engine is designed to run best with at least 20% nitro, but no more
than 30% nitro content. If you like a more “drivable” engine, choose 20%; if you like a lot of horsepower choose 30%.
Whichever type you choose, use the same fuel for break-in and everyday operation – for the life of the engine. Don’t indulge
in the “fuel of the day” game – it only hastens the day when you will need a new piston and cylinder-sleeve set. Here’s why:
Increased nitromethane content in the fuel causes combustion chamber temperatures to rise. This is normal since nitro is the
primary power-producing ingredient in the fuel’s chemistry. As the temperature increases, so does the expansion of the piston
and cylinder-sleeve. As described previously, the chrome-plated sleeve is engineered to expand more than the aluminum alloy
piston – as controlled by the cooling ability of the cylinder head fins. With higher nitro content fuels (e.g., 30%), the piston to
cylinder-sleeve running-fit (clearance) is a bit larger than with lower nitro fuel blends – it’s the nature of the beast. Therefore, if
you start by using 30% nitro fuel at the beginning of your engine’s life – with its tight pinch fit when cold – It will produce the best
possible WOT performance characteristics, if you continue to use the same fuel for the life of the piston and sleeve.
If you change fuel – reduce the nitro content to say 20% - the engine will run good, but a bit of the pinch will wear away from
the top of the piston because lower cylinder temperatures equate to less expansion of the cylinder-sleeve. If you then decide to
switch back to the higher nitro fuel, the elevated temperature and expansion will produce greater piston clearance (due to its
previous wear using 20%); the elevated quantities of blow-by combustion gas will cause the engine to lose power.
These principles also hold true for oil content. By changing oil content, you may affect the temperature that the engine will run
at, which in turn will affect the piston / cylinder-sleeve clearance, as described above.
The moral of the story is: It’s best not to change fuel, once the break-in process has began, however, if you plan to switch fuels,
start with the highest nitro content and/or highest oil content and work your way down … never to return! Of course, there will
always be the individual that thinks the single fuel theory isn’t valid. After all, his engine runs faster with his latest switch to high
nitro content, until he meets-up with a single-fuel high nitro guy – who blows his doors off!
2. Start your engine following the starting procedures previously covered.
3. IMPORTANT: Once started, begin running your truck around immediately, as described in step 4 below.
Since it is a true ABC-type design (high silicon content aluminum alloy piston running inside a hard chromeplated
brass cylinder-sleeve), it should be brought-up to temperature as quickly as possible, allowing the sleeve to expand
enough to achieve optimal fit; otherwise, the piston will scrub the sleeve excessively, causing premature wear, loss of
compression, and diminished performance.
4. Here’s the tricky part: to the best of your ability, immediately begin dialing-in the high speed needle valve for maximum rpm
performance during the first tank of fuel. During this period, cycle the engine between WOT (full RPM) and idle in 5 to 10
second intervals, by making high speed passes, on the type surface you prefer to operate on – this will keep the piston and
cylinder-sleeve hot enough while the operator tweaks the needle during quick pit stops. A helper is very handy for this critical
operation! If the engine quits before the idle is set, that’s okay – just allow the engine to cool off – heat cycling is part of the
break-in process. Ideally, get the needle valves set for maximum performance and a reliable idle as quickly as possible
(see the Needle Settings section of your manual for more detailed information). If performed correctly, the engine should be
running near normal operating temperatures for the entire break-in process. Depending on the operating surface, outdoor
temperature, etc., your break-in temperature will range between 220º and 260º F. Following the above procedures, run the
engine for a complete tank of fuel – then shut it down. Allow the engine cool down COMPLETELY before re-starting.
5. Continue this process for about 4 tanks of fuel; this heat-cycles all the metal parts inside your engine.
IMPORTANT: Do not let the engine sit and idle for its break-in. The piston and cylinder-sleeve will not get hot enough to expand
properly, and the critical pinch-fit will disappear before you know it. In fact, we are more concerned about running an engine too
cool, rather than too hot!
