[steve25]

Thanks for the info!
With your 6X heads the stock valve length is 4.980”, and the stock spring installed height is between 1.560” and 1.580”.

Are your new valves 4.980” long which is for the low comp heads like yours, or do you have the next length up at 5.095” or so which are stock length for the high comp heads?

The Crower 405 springs are calling for a 1.700” installed height, so they will not be a simple drop in with stock 4.980” length valves.

If you want to say with Crower parts then you need there 68407 springs and there 87048 retainers .

If you have the 5.095” longer then stock valves then the 405 spring is pretty much a drop in!

All this info is just in terms of the heads, so now on to your Cam pick .

The 407 spring is only good to .450” lift and that cam with just 1.5 rockers has .470” lift!

Now add 1.65 rockers and your up at .516” lift!

The 405 spring is good up to .600”, so that’s the way to go, but that then commits you to either running the 5.095” long valves or machining the spring pockets to get that 1.700” installed height.

In terms of lifters and the open spring pressures you will be running with that cam and 1.65 rockers I would opt for the superlube ones!