Domed piston TDC measurement

[Steve D.]

This may be a silly question, but ....A piston stop bolted on the deck will stop a domed piston when the top of the dome reaches deck height. Is this considered TDC? I thought the dome travelled into the head chamber slightly.

Steve

[Duke W.]

Re: Domed piston TDC measurement

The zero reference line of a piston is the "crown". The dome extends above the crown and the valve notches below. The crown on most pistons is a machined flat area under the quench zone of the head, and an annular ring around the outside top surface of the piston may also be machined to crown height.

This established crown then becomes the zero line to drill the pin hole, the center of which should be within a thou of the nominal design distance between the crown and pin axis.

Duke

[Bill Jackson]

Re: Domed piston TDC measurement

TDC is exactly half way between where the piston stops when you turn the crank both ways till it contacts the stop.