rustylugnuts

What is considered aggressive cam ramping? I'm aware solid lifter cams have aggressive ramping, when compared to hydraulic lifter cams. If you take the advertised duration and subtract the .050 duration, this is considered your ramping number. Old school camshafts show higher numbers slower ramping easier on drive train, designed for longevity. Today ramping is very aggressive, faster ramping more power under the curve, also premature wear do to stress on valve train.

My question: Is there a cut off number?

rustylugnuts

65tripleblack

The old 30-30 cam has .050 duration of 254/254 and measured duration @ .006 (advertised/ SAE 1604D) of 346/346, for a difference of 92 degrees! The smallest difference I could find in Comp's catalog is 26 degrees. Other cam grinders may have faster ramps, but that is probably the limit for flat tappet lobes. I expect that a cam with ramps this aggressive would not last more than a few thousand miles if driven on the street. Most of Comps' Extreme Energy ramps are between 35-40.

rustylugnuts

That is a huge difference 92 degrees must look like a roller cam lobe...ha ha ha!!! On the other side 26 sounds like it will gouge the lifters, this must be full pro race. You have definitely found opposite sides of cam ramping. Comp cam is known for aggressive ramps 35-40 is great for strip/street, that is more strip then street use. So if 92 is extremely slow ramping, and 40 is aggressive ramping. Then a good starting average would be 66. So 53 to 65 would be considered moderate fast acting, and 67 to 79 moderate slow ramping. Got it!

Amazing how ramping of cam lobes matches horse power curve on dyno graphs. The steeper the cam lobe the more hp it makes but when it peaks out and drops like a led balloon.
On the other side slower ramps take a few more rpm's to produce the same hp, but holds on much longer with a much slower descend of the graph curve.

It's a trade off, quicker action (more aggressive ramps) quicker acceleration and torque at the expense of shorter life. Slower action (softer ramps) moderate acceleration and torque at the expense of longer life. My search is for a camshaft that has a happy in between ramp, if there is such a thing..... Thanks!

rustylugnuts

427Hotrod

This is VERY difficult stuff to compare. A huge factor is the point it is checked at for the advertised duration and if lash was involved. The GM one listed is using .006" tappet rise which is what is giving the insane duration number. It's a relatively slow and soft ramp so it takes a lot of rotation to move the lifter much. You'll find Comp rates some cams at .015" and some at .020" depending on lobe...so again...you will get vastly different ADV duration numbers.

Even in solid roller cam territory...you will see 28*-31* as being pretty serious stuff but will live at least a decent life.

I often use a little Crower circle track flat tappet in milder small blocks that shows 236*@.050 and 268* adv. That's a pretty *quick* lobe for a flat tappet...but runs killer...and lives.

Using lifters with EDM oiling helps keep things alive on all of them.

JIM

65tripleblack

Tight lash cam, that Crower?

EDM oiling is not as important in a SBC as in a BBC. Not needed in a SBC, especially with today's piddle valve lifters which send plenty of oil through the pushrods and down into the lifter valley to bathe the cam. If you can find edge orifice lifters (which are used for roller lifters, and which were once used for flat tappet lifters) then you might consider EDM oiling with a SBC. That is just my humble opinion. More important than the amount of oil reaching the cam lobes, at least in a SBC, is the zinc/phosphorous content of the oil, as well as the dispersant levels contained in it which helps keep the oil attached to metal surfaces.

As far as lifters are concerned, I just bought a set of these, which come highly recommended:

http://www.lyonsperformance.com/valv...0bbda9f570aa99

Inspection reveals a larger convex "hump" on the flats, a very highly polished surface on the flats, and the inscription "Johnson Lifter, Romulus MI, USA" within the oil relief. They are advertised as containing a higher amount of acicular carbides on the cam face, than most other lifters. This last fact means nothing to me as I'm not a metallurgist...........it's probably their way of saying that the lifter is made out of a harder grade of cast iron.

rustylugnuts

How can one tell if the lifters are the piddle valve type? I have a old never used set of TRW VL43 just below that number is SP AT-992 solid lifters. I see nothing mentioning piddle valve. Also am looking into custom cam grinding. This is what I'm going to suggest for 283cid/315hp fuelie. But will first be installed on a rat rod 283.

1961 Corvette Suggested Profile Solid Lifter Camshaft

.454 Int lift… .464 exh lift... Dur@ .050 lift… 229 Int... 234 Exh... Adv Dur… 285 Int... 290 Exh... LSA 110… 108 ICL /112 ECL… Overlap 67.5.… Int lobe Ramp 56…… Exh lobe Ramp 56…… Int Opens BTDC 7.5…. Int Closes ABDC 41.5…. Exh Opens BBDC 52.5…. Exh Closes ATDC 1.5
RPM Range 1600 – 6200 - 1.5 rocker arm ratio. Valve lash (Hot Int .012 Exh .018)… (Cold .014/.020)

Any thoughts? rustylugnuts

65tripleblack

Here are both types of solid lifter:


Edge Orifice


Piddle Valve

The edge orifice type has the oil feed hole outside of the oil groove, so it is only exposed to oil pressure during part of its stroke. The piddle valve type has the oil feed hole within the oil groove, so it is always exposed to oil pressure. Flow is metered by means of an orifice plate just below the pushrod seat.

rustylugnuts

I opened up a box to check. it has the oil feed hole within the oil groove, it's the piddle valve type. Appreciate the definition and the detailed cross sectional views. Well back to the garage.

rustylugnuts

rustylugnuts

That can be deceiving when comparing camshafts. The cam manufactures should agree on another measuring standard, but then I guess it also can be to their advantage not to, or they would have already done so .

rustylugnuts