hey, i wanne use 25% nitro
instead of 16% nitro fuel
in my touringcar engine.
cause i am a 1/8scale driver for normal
what to do with engine? less/more shims?

greetings

16% for 1/10,25%for 1/8,you need to retune your engine setting if you change from 16% to 25%

wasnt my question
im clear that i have to retune it
read again please!

More nitro must need more headshims. to make that step you must add 0.1 or 0.2mm of shims.

add 0.2 shim
you should mention run 25% with .12 engine

Hi, I have a similar question.
I'm using a cheap 8 port .21 for practice (sh engines pt21xt2-p8). Actually the performance of this engine is not so bad but I would like to bring it closer to my race engine and am thinking of trying a higher nitro percentage fuel, maybe 28 or 30%. Runtime is no issue as just for practice but will wear be much higher? Should I shim the head up? Change plug?
Will it actually have much more power, and where in the power band?

Thanks.

No, you do need to change some internal timings and maybe improve some flow to get more out of such an engine.