Originally Posted by Bawana (Post 4359689)

Great find.... Exactly as I said too much spring robs power. Mild when do you have time to work? you seem to spend a ton of time doing research, which is great for everyone on OSO but your wife must never get any time to .. well you know.... LOL

Originally Posted by MILD THUNDER (Post 4359709)

it doesnt take me long to get things done :)

Originally Posted by 10x (Post 1123714)

Yeah... That's what they all say, but only to extend the life of the lifter.
I tried 140# on the seat and about 385# at 600 lift, and with a mild (230-235) duration cam everything was fine till 5600 rpm. No matter what I did, the engines fell flat at 5800. End of the season I pulled the engines to make a few changes.When I lifted the heads to check the valve springs, cause I found signs of valve float, I found almost half of my valves were being pushed through the retainers. Some stems were flush with the locks. Bottoms of some of the roller rockers were hitting the retainers.
What a F'n mess. Bottom line here is no one expects you to run more than 5450 rpm. I think that's what the mercruiser rev limiters are set for at the factory. When you start going over those rpm's, those light v/s combinations can't handle it.
I had valve float so bad, it's a miracle i did'nt lose a valve.
After many lenghty conversations with a marine (offshore) technication at Crane, he finally gave up the truth on spring pressures, rpm's and longivity of hyd. roller lifters. And if you want to turn 6000+ rpm's and make the bigger hp, you CAN'T expect your valve train and especially hyd rollers to last. It cuts their life in half, at the best.
Now we run 175# on the seat, and 490# at 650 lift, and hav'nt had any valve train issue in 2 seasons.

Originally Posted by Reed Jensen (Post 1131384)

There is a common misconception that the energy to compress the springs is lost.. not so.. the majority of it is returned on the back side of the camshaft. The energy that is lost is called hysterisis, which is internal friction in the spring itself. This is what causes the spring to heat up. If you were to graph the opening and closing rates on a linear graph.. then it becomes obvious that the valve is lifted off the seat, accelerated to full opening.. and then decelerated and slowly lowered onto the seat... The spring pressure isn't as big a factor on wear as you would think. But.. having the valve not follow the cam,,, the valve then "crashes" onto the seat.. This is much more damaging. Also it tends to hammer the keeper into the valve spring retainer. If you are using light weight retainers, they will begin to expand in the area of the keepers and quickly fail. Sometimes they will fail when not even running the engine hard. They have just give up and let the valve keepers slide through.

Originally Posted by ICDEDPPL (Post 4359726)

Mikes @ High Flow likes higher spring pressures, I forget his explanation but I trust his expertise. Your valves and seats are probably TIRED from all that bouncing around with that low seat pressure.

Originally Posted by ICDEDPPL (Post 4359726)

Mikes @ High Flow likes higher spring pressures, I forget his explanation but I trust his expertise. Your valves and seats are probably TIRED from all that bouncing around with that low seat pressure.

Originally Posted by abones (Post 4359720)

I run a moderate lift/ duration hyd. roller with 175-442 springs all i need to keep the valvetrain intact.we run for extended periods at 6k and above. My belief is that you must be able to close the valve gently enough not to damage it but with enough authority to keep in on the seat at higher RPMs I also believe that the closing pressure is engine specific to what you are trying to accomplish. I>E> n/a, turboed, Supered, NOS, etc. (as Mark expliained in his post)

Originally Posted by articfriends (Post 4359724)

I run 190 seat/490 open but at 14 psi of boostwe are adding extra to acct for area of valve x boost trying to force intake open