piston stop tool - adjustment?

[elorenzof]

Why does the piston stop tool have an adjustment? How do you know how far to adjust it in to correctly find top dead center on cyl # 1? It seems to me if i adjust it in and the piston touches it, then you have tdc but if you screwed it out then the piston would raise more and touch it again, then you have tdc. am i complicating things? Basically i know you screw it into the cyl # 1 but how do i adjust the inner portion (how far) to find tdc

[68BlueBeast]

If I remember right from my last cam install years ago, you are supposed to adjust the stop so the piston is at a certain distance in the hole. Then you spin the engine one way and check the mark on the degree wheel, spin the engine the opposite way and check the mark on the degree wheel. Then, you place the engine halfway between the two marks and zero the wheel. That would be your TDC. You can also use a dial indicator on a bridge to bring the piston up and find TDC by needle movement.

[tdangle]

Originally Posted by 68BlueBeast

If I remember right from my last cam install years ago, you are supposed to adjust the stop so the piston is at a certain distance in the hole. Then you spin the engine one way and check the mark on the degree wheel, spin the engine the opposite way and check the mark on the degree wheel. Then, you place the engine halfway between the two marks and zero the wheel. That would be your TDC. You can also use a dial indicator on a bridge to bring the piston up and find TDC by needle movement.

As 68BlueBeast said. The adjustment is arbitrary. It just stops the piston at a fixed distance. Rotate each way to the stop and 1/2 way between the 2 stops is TDC.

[Killer Bee]

really depends what you're doing to determine the accuracy required of the 'top'

for a simple distributor swap, bar the engine around until #1 is coming up on compression and stick a plastic straw, wood dowel, etc. in there and bring it up to where it crowns, drop the distributor in the hole pointing to #1 and follow firing order the around the cap the direction the rotor turns.. that puts you pretty dang close to 0 btdc and stock or near stock engine should start easily and run just fine so you can continue with base timing adjustments and follow up with final timing adjustments.. then send that tool back for a refund

if you're doing some other more intricate work, valve work, or cam installation, creating a timing scale, etc. you may need a little more precise positioning..

sooo, what are you doing?