I got new ARP studs in my connecting rods and I’m trying to check the clearance with plastigage. I remember before I took them to the machine shop I could take them off by hand with a little trouble. Now I have to use a brass punch and a hammer to get them off and really have to hit them hard too. I think its really messing up my plastigage readings because my readings are coming out to be way too small. My question is should they be this hard to take off?

yes they can be very hard to take off, there is a tool for that. I would not recommend hitting them with anything.

i use a wooden handle of a hammer with the rod in a wood vise and a leather mallet to tap on the handle

What is this tool called?

connecting rod splitting tool

summit part # PRO-66773

not cheap, like $110

That tool wont help me take it off the crank so i can see the plasigage reading. What kind of damage can happen by hitting it too hard?

sorry didnt realize it was on the crank, oops. If you have to hit it with something make sure is a brass piece or wood, like stated above, and use a dead blow hammer of some kind not a metal one.

has the same problem couldn't find a way to get it off except, put the rod nut back on and hit the nut that will make the piston go up and the rod cap off,works every time but be careful..

but that will still screw up the plastiguage... why not just mic them?

This won't help plastigage readings if the plastigage is under the rod cap bearing. Fortunately I haven't had to fight with "good" rod studs or I could be of more help. I always grabbed the cap with those 4" slip joint pliers and "wriggled" a lot. This isn't a good way either.
Even worse is not getting an accurate reading from the plastigage...

ohh srry

Instead of putting the plastigage on the cap I put it on the piston side of the rod so it wouldn’t get the taps from the hammer. The plastigage is coming out to say .001 when the book says it should be .0018 -.0032 or something like that. How reliable is plastigage? What should I do now?