Geoff2 wrote:I don't see how you will get '100% of the lift' with a hyd roller because it bleeds down as it passes over the lobe...
Unless something is wrong or mismatched it does not bleed down as much as you might think.
However lift loss from oil compressibility due to air entrainment (especially with full travel lifters) is a bigger problem than most realize... Oils have been formulated to minimize same.
Worst loss of peak lift that I've seen with a reasonably well matched set of parts (including full-travel lifters) and widely available synthetic oil was .015".
Some of that loss was compliance of the parts. Nothing exact to offer but a "nicer" cam lobe design reduced loss of lift to .010"-ish from .015.
Everyone sees something different, but I can tell you I saw more fuss points & worse overall performance with limited travel lifters compared to full travel.
If it lost 0.015"at peak lift, then by the time the valve is close to seating, considerable duration has also been lost because the valve spring force continues to bleed the lifter down as the lifter rides down on the closing side of the lobe.
With a sol lifter, once the lash is set, what you see is what you get in duration & lift....
Not to stray off topic too far but just to clarify: In my example, the lift was checked with a solid lifter and an actual as-run hydraulic race lifter (limited travel but with hydraulic metering).
Checked at the retainer, there was no difference in lift. Spring pressure: 200 closed and 400 open. Push rod cup height in both lifters were identical.
Geoff2 wrote:If it lost 0.015"at peak lift, then by the time the valve is close to seating, considerable duration has also been lost because the valve spring force continues to bleed the lifter down as the lifter rides down on the closing side of the lobe.
With a sol lifter, once the lash is set, what you see is what you get in duration & lift....
It doesn't work like that. Do some testing and you will see what I'm talking about.
Geoff2 wrote:If it lost 0.015"at peak lift, then by the time the valve is close to seating, considerable duration has also been lost because the valve spring force continues to bleed the lifter down as the lifter rides down on the closing side of the lobe.
With a sol lifter, once the lash is set, what you see is what you get in duration & lift....
It doesn't work like that. Do some testing and you will see what I'm talking about.
What actually happens will depend greatly upon the particular hydraulic lifter and the amount of acting valve spring pressure.
Geoff2 wrote:If it lost 0.015"at peak lift, then by the time the valve is close to seating, considerable duration has also been lost because the valve spring force continues to bleed the lifter down as the lifter rides down on the closing side of the lobe.
With a sol lifter, once the lash is set, what you see is what you get in duration & lift....
It doesn't work like that. Do some testing and you will see what I'm talking about.
What actually happens will depend greatly upon the particular hydraulic lifter and the amount of acting valve spring pressure.
Right, and if all is well to begin with the dynamic trace will show (more or less) similar losses in similar areas compared to a solid lifter combination.
I think some of these guys have vivid imaginations that make them believe the hydraulic lifter is bleeding down or pumping up at some profuse rate/amount.....Unless something is big wrong that don't happen.
If the hyd lifter[ed] engine lost 0.015" lift at peak lift, the same forces causing the 0.015"lift loss will continue to cause lifter to bleed down, with the resultant loss of duration. Even if there was somehow no further bleed down after the loss of 0.015" at peak lift, there has already been significant duration loss. Nothing to do with a vivid imagination, just physics...
With a sol lifter, the only way lift could be lost would be valve train flexing, which would also affect hyd lifter valve trains.
You're assuming the loss of lift was due to the lifter bleeding down......It wasn't. Some times you see the same thing with a solid.
Geoff2 wrote:If the hyd lifter[ed] engine lost 0.015" lift at peak lift, the same forces causing the 0.015"lift loss will continue to cause lifter to bleed down, with the resultant loss of duration. Even if there was somehow no further bleed down after the loss of 0.015" at peak lift, there has already been significant duration loss. Nothing to do with a vivid imagination, just physics...
With a sol lifter, the only way lift could be lost would be valve train flexing, which would also affect hyd lifter valve trains.
What kind of rpms are we talking about here for hydraulic rollers? Lsx valvetrain is typically pretty light weight with the 8mm stems, some hollow valves.
Guys are turning 8k rpm with hyd rollers these days. And making good power. I dont see why solids are needed unless full on race car with super aggressive cam lobes.
Even boosted guys are goin fast. Think the record ultra street or something 76mm turbo lsx was mid 7's et with a hyd roller.
Orr89rocz wrote:What kind of rpms are we talking about here for hydraulic rollers? Lsx valvetrain is typically pretty light weight with the 8mm stems, some hollow valves.
Guys are turning 8k rpm with hyd rollers these days. And making good power. I dont see why solids are needed unless full on race car with super aggressive cam lobes.
Even boosted guys are goin fast. Think the record ultra street or something 76mm turbo lsx was mid 7's et with a hyd roller.
A properly designed cam lobe will run "clean" above 8,000 with all stock parts except the spring.
Orr89rocz wrote:What kind of rpms are we talking about here for hydraulic rollers? Lsx valvetrain is typically pretty light weight with the 8mm stems, some hollow valves.
Guys are turning 8k rpm with hyd rollers these days. And making good power. I dont see why solids are needed unless full on race car with super aggressive cam lobes.
Even boosted guys are goin fast. Think the record ultra street or something 76mm turbo lsx was mid 7's et with a hyd roller.
Don't mistake the Morel limited travel lifters, with true hydraulic lifters. They're actually just solid roller lifters with a little bit of movement. They were designed for racing applications that require hydr lifters. That small movement bleeds off under pressure, and they become solid rollers with a small amount of effective lash. in them.
I wasnt refering to those limited travel stuff. I used regular morel 4602's in a sbc with a heavy 2.10" valve to 7200 rpm under 30 psi boost and never had a control problem. I bet it would have gone to 7500 but it was well beyond powercurve at that point. Possibly not enough duration/lift/head/turbine etc. just been very impressed with hyd roller stuff, especially on the lsx oem type rocker system
CamKing wrote:...Don't mistake the Morel limited travel lifters, with true hydraulic lifters. They're actually just solid roller lifters with a little bit of movement. They were designed for racing applications that require hydr lifters. That small movement bleeds off under pressure, and they become solid rollers with a small amount of effective lash. in them.
If one accepts the theory that premature roller wear in street operation with aggressive high lift solid rollers is largely due to their stop/start/skidding at idle and low RPM, such a design could be a great fix by encouraging continuous contact while maintaining an appropriate operating lash.
CamKing wrote:...Don't mistake the Morel limited travel lifters, with true hydraulic lifters. They're actually just solid roller lifters with a little bit of movement. They were designed for racing applications that require hydr lifters. That small movement bleeds off under pressure, and they become solid rollers with a small amount of effective lash. in them.
If one accepts the theory that premature roller wear in street operation with aggressive high lift solid rollers is largely due to their stop/start/skidding at idle and low RPM, such a design could be a great fix by encouraging continuous contact while maintaining an appropriate operating lash.
That is what a rev kit is for, in my understanding
