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If you are just going to race it then 300 plus seat is fine but if you plan on driving it you will find out that is a problem!!

Just for a setup to compare I run less than 200 seat on hydr. lifters to 7200 and no missing even with 20 pounds of boost pushing, trying to stop the valves from closing. Look at valve weight and total valve train weight to know the real answer as the spring pressure has to deal with the valve weight, lifter weight, pushrod and the cam grind/ramp will change this answer. You can just over kill it and set it at 300 plus but like I said, thats not a motor that will not have an issue if you street it.

You want as little spring pressure as you can because higher pressures eats HP, are harder to start by taking more starter/batt to turn them over and high pressure springs wear out faster. Bigger is not always better unless you really need it.

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All that said, isn't the valvetrain on a BBC notoriously heavy? I think that would explain the use of higher pressure spings.
Big Blocks are going to take more spring than small blocks but almost 350 closed most likely puts your open pressure around 700 to 800 hundered on a big block with the added lift they run. You better have some super duper pushrods, shaft rocks and the best lifters you can buy and it still may break that stuff. Those are pressures we use to run to turn a BB 8500 RPM's and it ate valvetrain parts doing it. You really flex stuff bad at those pressures.

Go with what the cam company says to run. They have done the testing to know how much is enough to keep everything working correctly. All my point was if you are breaking valvetrain parts now, adding spring pressure will only make that problem worse unless you have too little spring pressure and the lifter is floating off the cam at higher RPM to cause the lifter damage.
 
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