mmb

I know what the guys that make serious power on all motor high rpm engines think about spring pressure. I have built and raced 9000 rpm engines and watch them pick up 60hp from removing excessive spring pressure.

abones

I think we all agree that a valve train should have enough open AND closed pressure to function at a desirerd RPM and no more than needed

MILD THUNDER

Youre missing my point. Your comparing a 256/260 camshaft, with .714 lift, to a 241 * camshaft, with .681 lift. Its no secret that as duration goes up, so can the lift. Its very possible that a 256/260 cam with 714 lift, can be less intense than the smaller cam.

Im with you on the over springing thing. But it has to do with how the lobe is designed, and certainly not going to detemine a lobes intensity based on its .050 numbers or lift numbers. If you dont have enough spring to keep the lifter from lofting on a steep lobe, you will have problems. The shape of the libe is what determines that requirement.

If i was building a 600 inch engine, with a long duration cam, i would have no issues with a 680 lift cam. Short 241 cam, more than likey the additonal lift isnt going to do squat on the speedo, and the focus should be on the timing events being proper, coupled to a lobe that sets the valves down easy. Unless of course we are talking about a bracket car, who doesnt mind pulling things apart all the time, and wasnt to squeeze an extra 12hp out of the deal so his cam makes more power than the catalog cam on the dyno.

mmb

Bro I love what you do and have no problems with you but Mike Jones lol Seriously??? Show me one engine that makes serious power on all motor that he has a cam in.

mmb

I'm not following your logic. A short lift, high duration cam is harder on the lifter than one with more lift. Basically what we call a square lobe cam. Lot of cheater cams run high duration with the lift cut down to class spec and they eat the living crap out of the valve train.

ICDEDPPL

Yeah? cause I thought that guy (jones) knew his stuff till he recommended a short duration, low lift cam and even after I argued that it`s all wrong that I don`t need low end tq and power he insisted making me doubt my choices. .612 lift on a big block that needs as much cylinder filling as possible?/ Yeah ok Mr. Jones. you can keep that 240duration cam.

Spring pressure also depends on what lifters you run. My high Rev morels require more pressure, you certainly don`t want that lifter pumping up mid stroke cause the valve floated.
I run 225/545. Valvetrain looks great.

Not sure about power loss with more seat pressure, at any given point you`re trying to lift a valve there`s another closing counteracting against each other.

MILD THUNDER

So, by following your logic, if i was to take a 502 magnum 224 duration, .480 lift camshaft, and switch to a 224 deg , .680 lift camshaft, my valvetrian would last longer?

Try selling that one to general motors lol. Hence why a 502 mag will go 900 hours without a valve cover off, and a hp500 wont go 350 hours with similar cam and .600ish lift.

The turbo guys tend to run short duration cams, to help build low rpm power off boost, with lots of lift. Those setups kill valvetrains, until they back the lift down.

Rather than argue theories, i'll look at what crane , comp, lunati, howards, mercury, and others offer in a cam application. Once I start seeing a trend in their patterns, i start believing. You can look at all their lobes, and when duration goes way up, so does lift. When duration goes way down, so does lift, with all things being fairly equal.

mmb

If you run that much pressure and the springs are staying consistent and not losing pressure you're fine. The next thing I worry about is the roller shaft breaking in the lifter. They always look good until they break.

The valves, retainers, rocker arms do not break very often.

ICDEDPPL

Low duration/high lift=beats up valve train
High duration/low lift= beats up valve train.


Marine/endurance grinds need to strike a balance between lift and duration. Lunati Marine lobes for example are easy on the valvetrain.

You want the lobe on the left for endurance not the ski slope on the right (probably great for a 10 second strip car)

ICDEDPPL

Sorry Tim you probably have the left lobe