Question about a piston stop?

Question

I'm using a spark plug hole piston stop to check for top dead center on my small block chevy 383 with dart heads and the piston will not reach the piston stop. I'm pretesting out some techniques for when I change to a different cam profile and just want to work out the bugs for when I use a kit that allows you to keep the heads on when doing the cam changout. Why would this be doing this? And I'm guessing I will need to take off the heads to centerline the new cam.

Answer 1

cheap and easy way to find TDC is to use a phillips head screw and stick it into the spark plug hole on #1 cylinder.and as you turn the engine over by hand watch the screw driver rise and then start to go down turn back til it stops here is TDC and you don't remove the heads to degree the cam in.you need to have the rockers on and use a 1 inch dial indicator and a cam degree wheel to dial in your cam shaft.the CL on the cam shaft is the distance in degrees on the lobe seperation you can not change this with out making a new cam, the lobes seperation is fixed.and on the TDC the mark on the balancer should be on ZERO @ TDC.on the timing tab.

Answer 2

Indeed... The only way you are going to accurately and perfectly find TDC with heads on is to use a positive stop device. With heads off, it''s a dial indicator. How long is your stop tool..? You can get in the ball park with a screw driver, but are you interested in perfection or just "Government" work..?



So you want to play around with cam profiles..? You're in my domain now.

6 inch rods or shorter..? That's going to be a factor for what is most appropriate, as it's not just about heads. And always... A gentle closing ramp the last .020-.040 worth of lift on approach to the seat.



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Answer 3

Your piston stop is not reaching far enough into the combustion chamber to contact the piston.I made a piston stop years ago by breaking the insulator out of an old spark plug and threading the small end of the plug so I could screw in a bolt with the end rounded off to not scratch the top of the piston.

Answer 4

once piston is at tdc it will show better with a straw it will stay up as soon as it moves down a bit then you are losing tdc .some cars are set at 10 degrees below tdc .ok all the bes .very easy to judge .

Answer 5

If you really must use a "tool" to find TDC on your piston, you probably shouldn't be working on the engine.