4 x 4 Welder mentioned performance cams..

and said something about both intake and exhaust being open at TDC...

TDC occurs twice in the cycle... once between the compression /power stroke and
once between the exhaust / intake .

Lets confine this to TURBO 617 engines.

On Gas engines increasing valve overlap is one way of increasing power from the engine. This involves some waste of fuel compared to the lesser power same engine... but gets more air /fuel mix into the bore to be compressed.

Are the intake and exhaust valves both open at either TDC position of the crank and will a change in that relationship make more power on a turbo 617 ?

If some amount of air increase is possible by that method on a turbo 617 won't the amount of fuel per power stroke have to be increased to afford any extra power ? Is that feasible or is the relationship controlled by a cam profile in the IP ?

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html