Haven’t been here in along time,does anyone know the required spring rates for MP p4349268 .620 mechanical cam. They say to use the p4876064 springs but don’t show any spring rates,just max. Lift. Thanks

I don't know the pressures called for on that cam or on those valve springs either but I have a customer who had one of those cams in his bracket motor that I worked on. He broke a valve and bought a new set of 440 source heads instead of fixing the broken 440 Source head.
I think that I ended up setting the seat pressures between 140 to 150 lbs. and between 350 and 360 opened and had right at .080 to .100 travel to coil bind.
I shoot for .050 to .060 from coil bind on aluminum heads with roller cam valve springs, not so much on the pressure but more focus on the coil bind clearances, that has worked well on a bunch of Mopar BB wedge bracket race motors I've built I use to shoot for 225 Lbs on the seats but now I look for between 250 to 325 lbs. on the seats and from 680 lbs. opened to 840 lbs. open, depending on the cam grind, lobe design and intended shift RPM

Thanks Cab I’m going to be using a set of CnC ported stealths i picked up.(new in the box never ran) Hughes built them,but I have no idea of what springs are on them,they do however have 10* retainers and locks which to me would indicate a high spring rate. I’m going to take them to my machine shop and have them checked out so i know exactly what is on them. The specs you gave me are pretty close to what i have found searching around. D

Assuming 1.5 rockers, I’d shoot for 145-160 on the seat, 375-400 open...... for operation up to around 7200rpm.

For 1.6 rockers and/or more rpm, I’d be more like 400-425 open.

http://www.moparts.org/Tech/Archive/bb/3.html

The book says the 064 springs are 1.600" diameter to be installed at 1.86"-1.88" and have 146 seat pressure and 419 open pressure at a max lift of .640" and are made out of .216" wire.

Thanks much guys ,Really appreciated