I was wonding if a bigger cam would cause a different reading when doing a compression test vs the stock cam?

 

Yes it will.

 

Does it raise/lower it and how would one find out how much it would affect it by?

 

Here's a Dynamic compression ratio calculator that also does cranking compression. Don't know how accurate it is, but should be directionally correct. BTW, although it calls for intake valve closing point at 0.050", I think it actually needs advertised IVC:
http://www.rbracing-rsr.com/comprAdvHD.htm

 

Thanks for the link, now I just have to figure out all the information that's needed there to find out.

 

Longer duration usually means less compression on your gauge.
A stock cam may pull 220psi
where a much larger cam may only pull 150 psi.

the important thing with a compression test is that all cylinders read in the same range.

 

Ok so I found all the info to enter in there but when I do it calculates that I have 77cc combustion cambers and not the 66 that I should have. Is that going to throw off the compression readings.