this thread probably contains the most useful information for nitro throughout the whole forum.

I've got a head shim question. My engine came with .3mm worth of shims installed under the plug button. While measuring the piston at TDC and the plug button depth; my head clearance is at 1mm this seems way too much. I plan on running 30% I would actually have to remove the shims to get it close to the recommended head clearance of .55mm for a .12 engine. The best head clearance I can achieve is about .63mm (with no shims installed) I used my digital calipers to make the measurements any one have any Ideas. The engine in question is a Rossi/pixy .12 (gold head)

DIY ENGINE PORTING

That looks like a really good trick to try with a inexpensive engine. May have to give that a go when I get the "rainy day" car. And this is one of the most useful threads on the board.

the best way to learn is with a TRX .15 engine. they are extremely restrictive, and are kind of hard to hurt performance if you mess up. Heck, experiment with a worn out sleeve. Why pay someone to do the same damn thing when you can get more horsepower out of your mill ON YOUR OWN? Free is the way to be!

whatever you do, just dont polish any of the work you have done... thats just for looks and actually hurts performance.

Kemorc you are the man...I baught a TM G4S RTR, when I tried breaking the SH12 motor in I could not get the motor to run concistantly or even rev up to high RPM. I gave the car to a pro at my local shop, he recommended I send it back to TM (he said it was defective). Then I found this post and tried out your method and found two air leaks one on either side of the pinch bolt. Thanks alot, I can't wait to see how to car runs.

I also have a question, what kind of silicone is best to use for this application?

RTV works wonders.

I have been modding that way for some time and have been since my traxxas off-road days. I had so many guys send me their traxxas engines to mod it was not funny. Some may know me from the traxxas days as kcrunch racer x. Since the wonder years I have since found the on-road scene and have done the same mods on my engines and have had much success in getting some extra power out of them. and polishing is a joke only clean the piston top not its sides of the inside of a sleeve. Consider the bond between the sleeve and the piston one that should not be tampered with, because it will only kill performance..........

I am going to try this mod with an STS .12 mill. Should I break the engine in first or should I start with a fresh p/s? I can get one of these engines for about $100 USD shipped so if I trash it, no big deal. Thanks

isnt there also a way to check for the high end by the "spit test" and u spit on the engine head and if it sizzles a lil its ok and if it crackles violently is to hot or too lean. well i was wandering if this was an accurate and easy way to check the high end and the temp ? (i read this in a rc car bokk i bought but it was an older edition)

the high end needle is easiest to just set by feel, start where you know its too rich and then lean it until it produces the correct power a bit at a time. drive it around for 3-4 minutes at a time and make sure it doesn't start to lose power or feel different, that means you're close to too lean.

Do this and you'll see a crankcase shattering in thousand pieces. This is very bad advice to spray a very cold gas like the CO2 when escaping from the can to a hot metallic piece, no matter if it's a engine a body clip or whatever, the sudden cold put a lot of stress on the crankcase.

What suffers from flameouts he just needs to revise their own carb setting because it has a 99.999999999% and incorrect carb setting and/or clutch setting.

Did this happen to you?

Yep, happened to me in a .12 and NEVER tried more. Ruined a nice engine with the break-in just finished, and wasn't a nice scene.