Harold, on your 401A6LUN cam, you said springs should be 130 seat, 330-350 over the nose. I am being told by my machinist that I shouldn't go over 120 seat and 280-300 maximum over the nose for a street ride.BTW this is for a sbc 400. Which way should I go with the springs?

Thanks

Hey Jerry, I did check the Crane website for the spring specs on the sbc version of the F304 solid I ran ( after I replied to your email), and as I suspected, likely due to the better geometry and reduced sbc rocker ratio, the recomended spring pressures are only 120/296, not the 120/325 recommended for the bbc version.

Not speaking for Harold, but fwiw, methinks your machinist is correct.

Thanks Gene, appreciate you taking the time to check that out for me

Thanks again

Jerry, also checked the recommended Lunati spring, the 73100, is also 120/300 at .600 lift, so you'd come in under 300.

Sorry if I recommended the heavier spring ASSUMING it was a rat and causing you some consternation. My day job revolves around REMOVING consternation around complex decisions.

Anyway, I happened to check as I watched my Bears beat up the Giants! graemlins/thumbsup.gif

Better get back to my day job.... :eek:

Jerry,
The reason for more spring on a Rat is simply because of the weight of the parts you are controlling & the velocity of those parts with more rocker ratio, especially the valve, valve side of the rocker, retainer & spring.
In reality you have a lot less load on the cam with a small block than a big block with the same spring. 1.7 X 350lbs is more than 1,5 x 350.

As for seat pressure, a little more is in my opinion within reason not a primary concern as this is not what kills cams & is what insures the valve seats & doesn't bounce as badly.
You can run 120/300 more safely in a small block but again 130/330 is less load in a SB than a BB at the cam,, and also not to answer for Harold but I think his primary concern is that the valves follow his lobes as intended without killing them ;)

BTW, the spring also kind of depends on the RPM intended.

Bottom line, I feel either spring package will work quite well for a street deal but would lean towards the heavier of the two if you are going to be leaning on the right side pedal in a heavy fashion as that cam is capable of RPM'ing very well in a small block :D
If you are planning on 5500-6000 that's one thing but if your plans are for 6500+ ,,,,,

thanks for the info Mike. I am learning more every day. If I can just get some of this stuff to stay in my head long enough to get this motor built smile.gif