he asked if he needs roller rockers, so I doubt he already has a set. And the answer to his question is no.

the other thing he asked is if he needs different (shorter) pushrods. And the answer to that is also no, standard A12 pushrods will be absolutely fine if it is a reground cam.

Datsunb120, I can measure both A12 and A14 pushrods for you if you want to confirm you have the correct part.

What make of roller rockers are they?
If they are the YellaTerra rockers, then you can't use the original pushrods at all as these rockers need a ball at the top & the original pushrods use a cup.

first, is it a reground cam or a billet cam?

there is also a very real possibility that you have the cam timing wrong, and when tightening the rocker assembly down with the pushrods in place, valves are jamming on pistons.

the pushrods are the same lenght as the old ones, when position the rocker posts there is about a 5mm gap and it still does not line up when the rockers are completly loosened

would smaller pushrods solve this problem

Sounds like you haven't lined up the rocker posts correctly when you refitted them.

There are dowels in the bottom of the posts that need to line up with holes in the head.

If they are not lined up you would probably get about 5mm gap under the posts.

are you sure the pushrods are A12? A14/15 pushrods are substantially longer. That is the first thing to check and the most likely problem as far as I'm concerned.

reground cam or billet? if its reground then there cannot be a problem with the cam's base circle. Just completely loosen off the adjusters on the rockers and torque the rocker post bolts down - very important to use a torque wrench as they are stupidly easy to strip! And for the same reason it's not recommended to tighten them if the rockers are actuating the valve springs. You should be able to fit the pushrods with the rocker assembly in position. If you can't, I'd say you've got the wrong pushrods.

if its a billet cam and you still have this problem after confirming the height of the pushrods, then it would seem that the base circle has been increased on the cam. You would be entitled to an explanation from the cam supplier, and will probably require shorter pushrods.

btw, it wasn't necessary to remove the rocker assembly.

i have resently put a new cam in and there is a gap between the head and the rocker posts, the pushrods are second hand a12 ones. do i need roller rockers or different pushrods