Help with roller rocker setting up.

I have just put a pair of performer rpm heads on my 289 together with a set of roller rockers ... the thing is I am having problems setting the lash on this. I have set them by each cylinder at tdc on the power stroke, taking up the lash, then giving them another half turn. after doing them all and setting #1 again to tdc. I find that the intakes on 3 & 4 together with the exhausts on 7 & 8 are really loose and rattling about. I have got the manifold off and can see that it is very difficult to set any cylinder at tdc as one valve seems to close as the other one is opening. I have tried to check them by the *three position method* but when #1 is tdc the intake on #8 is quite a way open.
What shall I do? I think this was a problem before as I bent 2 pushrods with the previous heads
I can see when the lifters are right down at the bottom of their bores ... should I set each valve at this time? or is there a better plan??
HELP!!

Route666 said:

Perhaps you were setting them on the wrong TDC? You should do it at the start of the combustion stroke, that is when the valves will be closed. If you did it between the exhaust/intake stroke, the valves will probably be open slightly, causing the rockers to be loose when the valves close again.

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CORRECT !! What a fool I am .... that is what becomes of being in a hurry to get the car back on the road ... more haste less speed !!!