Originally Posted by gomer3245
I am running a Picco red dot 12 engine with 30% Byron fuel in a 1/10th sedan. What should I be running for head clearance with this setup? I am currently at about 30 thousandths clearance but the engine seems to be a little weak for power. Any suggestions for this problem? thanks.
Head Clearance For Picco based .12 engines
The “real head clearance” of Picco engines, when the piston is at Top Dead Center at sea level, can be calculated as follows:
Real head clearance = Thickness of head shims + 0.05mm*
* (that‘s due to the internal construction of the engine and the compression of the head shims, when the cooling head is mounted)
You may want to adjust the shims depending on nitro-content (see table) or track layout. Large tracks may require an extra 0.10mm shim to reach higher top speed and improved fuel consumption, but this will decrease acceleration slightly.
Nitro content: 16% 20% 25% 30%
Real head clearance: 0.45mm / 0.45mm / 0.55mm / 0.65mm
Head shims: 0.40mm / 0.40mm / 0.50mm / 0.60mm
Generally on a .12 engine 0.10mm will change the compression ratio about 3/4to 1 point.