Hypothetically speaking, there are two camshafts, one mechanical, the other hydraulic. The Duration at .050 , intake centerline, lobe separation angle, lobe profiles, and valve events are identical. The mechanical cam, however, does have an additional .019 lift to compensate for valve lash. As far as duration goes, are they truly equal? Numerous sources state that a mechanical cam needs an additional 8-10 degrees duration to equal a hydraulic cam. One source, however, says that the mechanical cam will make more power with the same duration as the hydraulic cam. I am aware that the advertised duration of a hydraulic cam is normally at 0.006 lift; whereas, the advertised duration of a mechanical cam is at 0.020 lift. Duration @ 0.050 lift is more reliable for both. Standing by for your two cents.
The mechanical flat tappet cam will perform the best. The low lift flow numbers are best with a solid lifter cam. With faster valve opening you have quicker cylinder filling. That is why most real high performance bad-boy engines were produced with solid lifter cams. Don't take my word for it, read some of the advanced engine development books out there by people like Dimitri Elgin and Alan Lockheed, Smokey Yunick,etc. You may begin to see the renewed interest in tight-lash (not monster-lift and duration) street rod cams. I have several small blocks running around in customer muscle cars with very good results.
I'm unaware of any cam profiles that were identical for hydraulic and solid lifters. From years ago, the ramps were more aggressive for solid lifters. Where are you going with this? What is your goal?
I'd question your amount of loss of valve lift on the hydraulic cam compairing the mechanical valve lash, I believe that it's more. I think the larger benefit of the mechanical cam is the weight of the lifter and valve float of the hydraulic cam. Your going to get a larger usable rpm sweep from a mechanical cam. I haven't used a hydraulic cam in a project car since 1983, and now there's problems with hydraulic lifters roller or flat tappet
I can use a C7 Corvette hydraulic roller cam as an example [don't flame me here] The LS series LT1 engine has that DOD [displacement on demand] lifters to cut 4 cylinders. The DOD lifters have lash so they can lock and unlock when they they are riding on the base circle. These lifters have a reputation of failing, so many owners make the mistake of simply swapping the lifters for non DOD variety. GM lengthened the duration on the ramps of the lobes an added a bit more cam lift to compensate for the lash [the lift and duration at the valve is identical] By adding normal hydraulic rollers to these 4 cylinders [with no lash] increases lift, AND in more importantly increases duration which bleeds off cylinder pressure on these cylinders. The engines then start idling rough and will throw a CEL So if GM increased the lift and the ramps on the lobes to compensate for lash. The opposite will happen if you used solid lifters on a hydraulic cam it would have less lift and duration [at the valve]
Obviously, I'm no cam expert. However, all else being equal, it seems to me that if lash is compensated by a like amount of lift, the mechanical flat-tappet's duration should be equal. Of course, solid lifters should be lighter, and less chance of valve float [sic] at higher rpm. Having a Ford Y-block, hydraulic flat-tappet and roller cams aren't an option.
To get the same valve duration on both cams the mechanical cam would need an earlier opening and later closing ramp. It needs to take up the lash before it starts to lift. [cam lift is valve lift divided by rocker ratio] Putting a hydraulic lifter on a mechanical cam is a cheat way to increase lift and duration. The lifter weight is secondary to valve weight due to rocker ratios [Valve float is easily controlled with valve springs.]
Hydraulic flat-tappets and roller cams aren't an option but running the valve lash at 0.010 will sure as heck make that sucker wind faster. Used to do it on my dirt track engines, worked great.
No doubt, a tighter/looser lash makes a difference. One manufacturer recommends .012-.015 cold; add .004 for hot.
I am not on here much, hence the reason for the late reply. I don't think your question was fully answered. You asked if the duration was equal on the different camshafts. The duration is a physical number and it doesn't end at .050 tappet lift. The actual cam profile design or a profile report would be necessary to compare the two camshafts. The duration at the common tappet lifts could then be compared. Usually .020, .050, .100, .200, .300, and so on. If the duration numbers are the same, then they are the same. If the duration numbers are different, then obviously they are not the same. The performance of the two camshafts is entirely different. They may perform the same even though the duration numbers are not the same. The profiles may have about the same area under the lift curve, this area is what the engine is actually responding to. One profile having lash and one profile having zero lash does not directly make one camshaft perform any better than the other.
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