edelbrock magnum head valve springs

In my experience, the springs are good for middling cams and lower rocker ratios: I have a similar hydraulic roller in my 408 (292/300 adv, 230/[email protected]", .528"/.548") and the stock Eddy springs allowed the engine to rev to almost 7000rpm with 1.5 rockers.

However, as soon I replaced the 1.5 Crane rockers with 1.65 T&Ds, the cam needed better springs - the heavier rockers and extra .050" lift overpowered them.

I'm now running about 170lb on the seat and 375 open pressure @.584" on the intakes and the engine revs well past 6500rpm.

Interestingly, the engine made more power after the rocker swap, but did it 500rpm lower (440rwhp @ 5500rpm vs 413rwhp @ 6000rpm). It picked up a bunch of torque, but lost a few hundred usable rpm up top.

So your choice is either new springs of go back to 1.6 rockers. You can fit LS-style beehives to Eddy heads - I have a set on mine - as they have a 1.800" installed height, .545" valve guide (.560-.570" LS spring locators will fit) and spring pockets sized for 1.480" cups/shims.

All you have to watch is LS valves are 8mm, so you will need to find 11/32" beehive retainers and locks to suit - but there are plenty to choose from.

The standard Edelbrock spring is part #5767, which is actually a Ford spring, and it is rated at either 344lb or 362lb - because Edelbrock advertises different rates for the same spring depending on which head it is installed!

For what it's worth, I think the [email protected]" and [email protected]" advertised specs for the Ford 429/460 head are closest, as my springs were pretty close to [email protected]" when I removed them - not 120lb.