Those D port heads can be had in a flat tappet version with springs hood for.575 lift before coil bind and shipped set up for 120 psi on the seat, the version of the heads set up for hydro roller use is shipped With springs that can handle the same .575 lift before coil bind , but shipped with 140 psi on the seat.
Since it sounds like you have already run these heads I would say you need the new springs and heres why.
To use the springs the heads where shipped with I would want you to add a .030 shim to make up for lost seat pressure .
With the .540 lift exh lift of your new cam adding the needed shim would you take you up to .570 when those as shipped springs are rated to coil bind at .575.
In short, yes get the new springs and set them up for 150 psi on the seat and then go and have fun!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!
1) 1940s 100% silver 4 cup tea server set.
Two dry rotted 14 x 10 Micky Thompson slicks.
1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.
Education is what your left with once you forget things!
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