Just exactly where is TDC on the cam??

[fishermanms]

I have installed new points, condensers and coils on this 1974 Johnson 6hp Model 6R74-C. I am trying to discover exactly where TDC is located on the cam. I have line up the points to the O, located in the word TOP. I know that wherever the points opens the most is the location, but to the naked eye, I could be off a little. So I was wondering if it is just to the left of the work TOP or to the right??? But I assumed it is dead center of the word TOP, and that would put me right on the O letter of TOP. Thanks for a little help....
Fishermanms

 

[iwombat]

Re: Just exactly where is TDC on the cam??

Dead center, or lined up with the shaft key.

 

[Scaaty]

Re: Just exactly where is TDC on the cam??

Just put the point (both) rubbing block on the top of any cam point lobe, a set it there at .020. Location of the crank irrevelent, as the whole ING plate moves anyway

 

[fishermanms]

Re: Just exactly where is TDC on the cam??

OK... I think I understand.. I line it up with the key in the shaft and when I thottle up the plate would be moving to advance the spark as you thottle up? There is no numbers or marks or anything for timimg... I assume the point gap would somewhat affect that? I dont need to worry about timing??? Just set the points and I'm good to go???? Thanks ... I appreciate all the help.
Fishermanms

 

[Xcusme]

Re: Just exactly where is TDC on the cam??

Simple procedure really....rotate the crankshaft until the crankshaft key way is aligned with the rub block on the points. (part that contacts the points cam (with TOP stamped on it)). Adjust point set for .020 gap.
Rotate crankshaft 180 degrees to adjust the other point set. Again, align the key way to the rub block and set point gap to .020. That's it.

There is no timing setting. As long as the crankshaft key is not sheared or partially sheared, your timing is set. If the flywheel nut is under torqued the flywheel can shear the key. Install the flywheel on a dry fit crankshaft taper, no lubrication of any kind.

 

[reload]

Re: Just exactly where is TDC on the cam??

The .020 setting of the points effects the timing. It is critical to be as close as possible to the correct gap. Also it is important to be at the high lobe of the cam.

edit: sometimes there will be a little mark near the word top, this is the location of the rubbing block for setting the points.

 

[fast_eddie]

Re: Just exactly where is TDC on the cam??

gap set too low and you burn up the points in short order. gap set to big and your engine will miss.

 

[Scaaty]

Re: Just exactly where is TDC on the cam??

Jeezz, get the point cam close, THEN JUST ROTATE THE THROTTLE PLATE!