Top Dead Center

Millstone Farm said:
Trying to set the valve lash on my Intek engine. How do you tell if a piston is at top dead center?
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With the valve cover off, spin the eng over by hand (slowly by hand only) you can watch both rockers open the valves then close....now when the Ex valve opens and it closes the Int valve will open next,as soon as it closes, look in the cyl to see when the piston is at TDC. Make sure piston is at TDC or you can still be on EX compression release.
 
As TDC approaches on the compression stroke a screwdriver is recommended to place in the spark plug hole to observe when the screwdriver quits moving TDC has been reached. I wouldn't put a screwdriver in my worst enemy's spark hole. I've seen too many engines that could be damaged because of the geometry of the spark plug hole angle and the cylinder bore. Use a drink straw in place of a screwdriver.

I'm aware there will be mechanics that will say - " I been usin a screwdriver for years, spit, spit " - you go right ahead but remember possibly a novice ask the question.
 
You don't need to find TDC to set valve clearance. In fact, you'll do a better job of setting the valves if you don't.

Exhaust Opening, Intake Closing Method.

Rotate the engine in the direction it runs until the exhaust valve just starts opening. Set the intake valve lash.

Rotate the engine in the direction it runs until the intake valve is nearly finished closing. Set the exhaust valve lash.

You will be setting the clearance with the cam follower on the base circle of the cam, directly opposite the peak lift portion of the cam lobe. No other method does this.

Exhaust Opening, Intake Closing. E O I C That's all you have to remember.
 
" a screwdriver is recommended to place in the spark plug hole to observe when the screwdriver quits moving TDC has been reached. I wouldn't put a screwdriver in my worst enemy's spark hole."

Well first off, the Service Manual *does not* recommend using a screw driver to find TDC. Second, B&S knows how to set the valve clearance on their engine which is piston 1/4" down after TDC.

Walt Conner
 
There are TWO "1/4 inch down from TDC" piston positions in a 4-stroke engine.

Which one does Briggs recommend?
 
On all engines be it auto, motorcycle, lawnmower, etc, TDC is taken to be at the completion of the compression stroke unless otherwise specified.

Walt Conner
 
With relation to the centerline of the cam lobes, where are the cam followers positioned on the cam lobes at this 1/4" down from TDC crank position?
 
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