In the Nitro Worx section of RC Driver it states that small-block engines have the head shimmed for 20% and big-block engines have the head shimmed for 30% nitro.........the 5.2 (.32) is a big-block, yet the manufacturer recommends using 18% nitro.
Could this be because Tamiya spec'd the motor to run on 18% or could it be that they don't want a rookie like me to hurt himself or the motor until i've learned how to properly tune a nitro engine.
They say you should break-in the engine on the same grade of nitro that you plan to run in it on a daily basis, maybe i'm being too careful, maybe i should just "damn the torpedoes" and fill er up with 30% Odonnell RTR fuel.
Should i follow the break-in instructions to the letter or can you recommend a better way to break-in the engine, some say that the motor should be started, allowed to heat up to 190degrees, cool completely, repeat 3 times, then give er the gun,or.............. drive it using 1/4 throttle or less in a figure 8 for the first tank of fuel, then another tank of figure 8's at 1/2 throttle or less, 3rd tank of figure 8's at 3/4 throttle or less, and then on 4th tank it's time to let er eat.
Any and all advice is welcome,
George

I would put 7 or 8 tanks through it without going full throttle .

ive known lots of guys that have ran 30% through the force .32 and .28 with out changing any shims...i myself have ran many force .28 with 30% with out a problem, and they say the .28 should run 18% nitro also....