340 cam in a 318

Bakerlite said
Farrrk.. Sometimes I don't know why I even bother to post here.
The drop at TDC is a reference point. From that reference, knowing the cam lift points at EVERY degree of crank rotation tells me how far the valve will be off it's seat ( obviously multiplied by rocker ratio) at it's closest position to the piston, which as you pointed out is not usually TDC .
Can I change the lift? Can I change the duration? Can I change how aggressive the lobe is? Can I change the LSA, what if I change the installed centerline or the rocker ratio when I'm looking to upgrade a cam without changing the base engine configuration?
Knowing the valve lift at every position of crank rotation ( piston location in bore) makes this possible.
Is this making your head hurt?
Spring pressure, valve train flex etc, usually increase piston to valve, compared to no load on the valve train..

No ****? Valve train flex INCREASES P/V??? No duh and that’s my point.

Your whole premise of knowing valve drop at TDC is just a number that means little without other numbers.

Most guys run WAY TOO MUCH P/V and kill compression with big, power losing notches because they used a method of measuring the clearance without the valve gear on.

Here is what you need. With a gear drive you can run piston to head clearance for intake valve clearance. That means if you have .040 deck clearance that’s all you need for intake P/V. If you have a belt drive add .020 and add another .020 for a chain.

Double that for the exhaust valve and send it. Now, if you have 450 on the seat and 1300 over the nose and 7mm stem valves with a 2.400 head, you’ll have to add some clearance because the valves will wiggle and hit things.

Does your head hurt yet? It should.