Has anybody got any info on roller rocker ie, what brands, how much, are they hard to fit, do they make a difference to performance. Thanks

The only person on here that I know of running them is Dattoman1000, When he pops his head up he will give you some info, I am not to sure if he has started his engine that has the roller rockers yet. But he will let you know.

I'm looking foward to a reply too, as i want to know if the rollers have a higher rocker arm ratio.
If they do, that translates to more lift at the valve for a given camshaft, & better yet, it allows a milder cam for a given engine output. I would rather go street cruisn' with a "sports" profile than a "race" profile anyday.

I have heard of rocker arms which have 1.5 ratio, but I too am all ears.

is there any other advantages?, do they put mose stress on any parts?, which way does the ratio work?, 1mm of pushroad lift = 1.5mm of push on valve???

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Thats right, at 1.5 to 1 ratio, 1mm of tappet lift - 1.5mm of valve lift.
If the ratio is higher than stock, then the pressure from the valve spring has more leverage against the cam & applies more force against it. Ratio improvements are usually gained by moving the adjusting screw closer to the rocker shaft. It doesn't take Einstein to figure out that there is only a limited scope for realignment here, but even a little can mean a lot.

With a higher ratio, the valve opens at the same time as before, but lifts a little quicker, & opens a little further than previously with the same cam. It stays open at a lift figure that is equal to, or greater than the previous "full open" figure, for a little longer. Finally it reseats itself at the same time as previously.

This means that it idles the same as before, but the head has better flow characteristics.

What do you pay for all of this?
Well, apart from the extra money it takes to buy them, the extra pressure exerted on the lobes would theoreticly increase the wear rate, but if the increase in pressure is relatively minor, & top quality parts are used, like stock Datsun stuff or better, then you will probably blow it up before you wear out these related parts.
If the rockers are roller types, there is a minor[?] reduction in friction at these roller points [rocker tip & shaft, as applicable] This may be enough to counter the additional load at the cam face in terms of total internal friction loads.

If you already have a high lift cam, it may be necessary to make absolutely sure that the valve springs don't coil bind, or that the collets don't bottom out on the valve guides. Thats when it gets expensive.
Again, if you have a high lift cam, you had better check the valve to piston clearance too, particularly if it was marginal before.

Depending on the engine, & the ratio increase, it may be necessary to enlarge, or elongate the pushrod holes in the head.

So that's the deal, a hotter cam without changing the cam, or the cam specs.
Depending on price, it could be an affordable & discrete improvement to your engines output.

It costs nothing to ask.

P.S. You may need to add a "thou" to your tappet setting.

Mine are YellaTerra units.
I am yet to fire the engine but it should all happen very soon. The tailshaft is in. I await the gaskets from JTS then I'll bolt the manifolds on and start it up.(hopefully)

Ratios available from yella are 1.55 or 1.65:1 You can option them in mixed sets if you want different inlet and exhaust ratios.
Mine are 1.65:1.
I'm using a small cam in this engine to start with till I get a handle on the car.........then I'll be changing to a bigger one when I do the engine freshen up and piston change.

I'll let you know how well it revs once its run it.

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Are these alloy or steel?
Are they roller tip only, or roller on the shaft as well?
Do you need a hardened shaft?
Are they affordable?
Did you need to modify the head in any way?

Your choice of a small cam to start with is, in my view, a wise one. If my rough mental maths is correct, thats a 10% increase in lift with the same cam. Thats gotta be a good thing.
The 1.55 to 1 ratio is only a 3.3% increase in lift, so the real benefit would be from the roller bearings & the reduced weight of the rocker if it is alloy.

I just went onto "google" and typed in roller rockers and got the Yella Terra site, worth a look, thanks for the info, i'm going to phone Yella Terra tommorrow, will post $$$$ and availability tommorrow

Like Lemonhead [what an unflattering name] i also checked out the Yella Terra site.

The only rockers that were listed on the site for the "A" series Datsun were the 1.55 to 1 ratio rockers which were on offer as a kit,[YT16023] containing the rockers, the shaft & the pedestals, which leads me to suspect that the ratio is increased by moving the shaft closer to the pushrods to allow rocker length variations.

Like others, i look foward to Lemonheads next post.