Yet another 273 build advice thread!
249/ 254 201/206 432 lift 112 in at 107 (+5) uses .858 of the .904 lifter face so it's not out to the edge and should wear well Hyd (or ask about a solid)
that's one size smaller than the 256 Lunati or Howards
how's that look AJ?
well I have to trust you that the time from advertised closing to actually closed is faster than most, because the advertised to .050 is not indicating it. 48* is a long ramp, am I right? So this could be another one of those; Yabut from .050 on, it is opening exponentially faster than so-and-so's cam, IDK, I'm not privy to that knowledge.
The thing I see, and am not fond of, is the 112 LSA that, in at 110 installed, generates a 55* Ica, and that is what I was trying to avoid. But again it all depends on what the Scr comes in at. If it was me tho, I would tighten up the LSA to something like 104, and let the meager overlap get lost in the logs. This has the double whammy effect of making 6* more pressure(perhaps 6 psi) with the same Scr, and 6*more more power extraction. This costs you nothing except the cost to move the centerline, if any.
This cam has a split of only 5degrees so you can't move it around much as a tuning tool without negatively affecting the other two durations, namely; the compression and power.
But the 249/254 numbers I think are right in the ballpark.
Your thoughts?
But personally,I wouldn't even bother with a hydro.
I'd shop for a tight-lash solid, and slam the intake closed as fast as possible still with as much .050 intake duration as I could get for this 250/255 net duration size of cam, adjusted for Scr and octane. Boy that's a mouthful of qualifiers.
The point is solids ain't everything and you can still get a crummy solid if yur not careful.
If you have a pair of
[email protected] cams, one a hydro and the other a solid, installed in a streeter, chances are they will make similar absolute power. The difference is in the power curves below the peak, and how they will perform in daily running. And that goes straight back to when exactly that pesky intake closes; the solid's actual after lashing, compared to the hydro's gentle landing.
I suppose it would theoretically be possible to find or more likely, have built, a really fast ramp hydraulic cam in this modest size....and
I suppose you could bad luck pick a terrible long-ramp, loose-lash solid from out of a catalog, and
in the end the hydro would run better, stronger,quieter,and be faster.
I suppose. .......But I ain't taking bets.
Cuz
to get a 249/255 solid tight lash, you might have to order a 254/260, which after lashing gets you the 249/255. But with this solid, you know EXACTLY when the intake is closed. Whereas with the hydro,that 249 is probably a .006 or .008 spec..... which means the dog-gone valve could still be off-seat for another 7 to 15 degrees(guessing).
Ok but you say, so what!. And you'd be right once the engine is wound up it matters not one iota. But when you put it into drive and the rpm comes down to 500rpm.... now it matters, to the guy with a DD/cruiser,or small engine. If your pistons are now pushing fuel-charge back into the intake, for 15 extra degrees you hadn't counted on, what is that doing to your cylinder pressure, and how is the engine gonna respond when you hit the throttle? Now it matters.
But here is the bigger picture, with that solid; since you can know the exact closing angle, and it is far less than the hydro, you can get a cam of at least one size bigger at .050, with no low-rpm penalty compared to the hydro.What's one size bigger worth?
IDK, it depends on the pressure, but it's not just about the absolute power, it's about the fatter than the smaller hydro, midrange. The more low-rpm pressure comes in awful handy too, especially with a modest sized engine, and modest rear gears.