TDC Indicator?

I made myself a positive piston stop out of an old spark plug and a bolt. The old Spark Plug is tapped so I can adjust the length of the 3/8 bolt once it's in the plug hole.

I'm just wondering how much of the bolt I'd want sticking out into the cylinder when finding TDC? Do I want the piston @ the absolute top of the cylinder? The motor is an SBC.

Thanks,

-r

 

i have a dial indicator i use for that sort of thing,you gonna be around tomorrow?

 

On most engines you can only approximate TDC with an indicator because there are several degrees of nearly motionless dwell at TDC, particularly on longish rod/offset engines like flatheads and SBC's. You use the piston device to STOP travel towards TDC twice, once while rotating engine CW, once CCW. Mark your degree wheel or pulley at each stop, find TDC halfway between.

 

yup, you wanta stop it well before the piston reaches TDC, the closer the crank throw becomes perpendicular to tangent the closer the sine gets to zero making exact calculations virtually impossible.

Try to have the stop adjusted to stop the piston at least 3/8" below TDC.

Paul

 

Yorg,

Do you mean today (Wednesday)? If so, yes sir I'll be around. The Cad is in San Jose & unable to move (finishing brakes, not registered, etc.) so if you're up for a trip over here, I'd be forever in your debt.

I used my piston stop to set TDC, but I tried to set a new timing mark & I didn't seem to do it right. The motor sounds good & will fire right up, but I'm having a problem getting it dialed in.

I'm less of an actual gearhead than I'd like to be. I'll pm you. Thanks.

-r