TDC Method Question
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From: Little Rhody
TDC Method Question Getting ready for a spring swap and will likely just use the TDC method, especially since I have a boroscope to confirm the piston position. How far will the valve drop prior to contacting the top of the piston?
Very little. I used a screw driver wrappred in Masking tape to find my TDC. The valve will drop about 1/2" if I remember right. But make sure you hold the valve stem and push it into the cylinder to see if it hits the piston to make sure it won't fall. 
Philip S.
Philip S.
it will only fall about 1/2 inch as stated above. I just used a wooden cooking skewer for finding tdc on mine. and just for insurance push the valve down LIGHTLY to ensure that it is hitting the piston then pull it back up because you are going to want as much of the valve stem as possiblr to work with.
I'm with these guys. It doesn't fall much, but I'd say it's more like 1/4". But that's just splitting hairs. Either way, it is a good idea to gently and slowly push the lifter down to see if it stops on the piston. You may not even have a chance to do that if you aren't at TDC. When you compress the stock spring, the lifter will likely fall as soon as the locks are free.
Thread Starter
TECH Senior Member
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Joined: Jul 2004
Posts: 8,092
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From: Little Rhody
1/2" is a lot, can you pull the valve up with a magnet? Otherwise, you need to compress the springs an extra 0.500 which is almost total valve lift plus the distance required to get the locks on.
