Hi, I've got my head back from the engine rebuilders today, with a new set of valve springs. They are are double valve spring made my "Perfomance springs"- i think. Anyway, my old springs had shims to bring the pressure up and they had about 90lb of pressure. The new springs from what I've been told have about 130lb of pressure! Is this too much for a datsun motor? How much can the valves/push rods handle? I haven't put the head back on just incase this is going to F*&k my motor again!.
Thanks

90 - 130 lbs isn`t to much of a problem.
What u gotta look out for is coil-bind at full valve lift! Check your cam lift then multiply by your rocker ratio, then make sure the springs don`t coil-bind at this lift!
Good spring pressure goes hand in hand with good cam profiles!
Dude it`s all good leave it at 130lbs and don`t panic !

Do you mean they shimmed them to 130lb? Because the 90lb you talked about is the preload ie with the spring installed with the valve on the seat. You're not confusing this with the spring rate?
I've got the same springs in my engine, shimmed to give 90lb on the seat. I don't know how much the valvetrain can handle, I'm not a pro, but from my understanding more than the minimum to prevent valvefloat is just wasting HP and will be added stress on the valvetrain.
If the head was assembled by an engine reconditioner then ask him, they usually know what they're doing.

130lb would have to be compressed, surely. . . Otherwise you will chew valveguides out in no time. Not to mention chewing out rockershafts. . .

In the past 70lb has been more than enough for 8000rpm plus.

The more load you put on everything, the more it wears.

Why is the head off? Wasn't a broken rocker or something was it?

Check for coil bind. Maybe you need to change springs. Something doesn't sound right.

The head was off because of broken valve spring (was the second time a spring had broken). I took it back to engine rebuilders who then fitted the head with a new set of springs (the dual springs). they said that the reason why the other ones broke was something about the spring rate for the cam?? And I'm pretty sure the guy said it was the seat pressure that was 130lb

I would look for another engine builder.

I would also replace the springs between the rocker arms with bushes. This will prevent the push rods bending under big revs.

Quote:

How does that work? What bushes do you use?