Hi so  i took it upon myself to put new 1641 barrels and pistons on my old 1600 case and when i got it back together the rockers seem tight on the valves when fully undone, i put the seal under the rocker mounts an done as per the haynes manual, are 1500 rockers different to 1600 as i may have used my brothers rockers or should there be a spacer under the rockers? (Im a novice so go easy on me  )

1200 ones are different but 1500 ones. Are the pushrods properly seated into the cam followers? There's no shims under the pedestals unless you're running swivel (aka elephants) feet adjusting screws. Have you tried rotating the engine so the valves have gone through their full opening and closing sequence?

Can you post a photo?

The 13/15/1600 rockers are all the same but even with the adjuster screws backed off all the way, it will still be trying to open a couple of valves as you tighten up the rocker shafts. so as David says, turn the engine over and you should see that you will get the clearance when the cam shuts the various valves 

Rob

It rotates fully but the adjusters are right back and when the valves are closed the arm seems tight onto the valve, i thought it would have some adjustment? I will double check the pushrods are properly seated in the cam end. Cheers for the replies

1641 are the same height as the 1600 so everything should fit as before. You will need to find tdc on number one then try setting the valves correctly rotate 180 degrees anti clockwise and do number 2 then another 180 for 3 then again do 4 just to see how it all goes.
Did you fit gaskets under the barrels then just bolt the heads on with no gaskets