Mapped out a solid cam while degreeing today

[My427stang]

I have always liked to try to figure out ways to compare knowns against unknowns, one of those things are comparing solid lifter cams to hydraulic profiles.

Solid lifter cams of course need to make up lash before a valve moves, some are rated at .015 tappet lift for adv duration, some are at .020, even Comp does some one way, some another.  Hyd cams are usually measured at .006 tappet lift and do not need to make lash up, so today I compared two cams.  The beauty here is I had both to measure and knew the performance of the 270H

The intake lobe on the solid cam from the cam card was 271 adv @ .020, 236 @ .050, 147 @ .200 and .333 lobe lift
The intake lobe on the hyd cam was measured, and from the cam card, 270 adv @ .006, 224 @ .050, 132 @ 200 and .300 lobe lift

To compare the 2 cams for DCR as well as general performance, I wanted to be able to compare the new cam's valve events to the 270H's on the same measurements.  That meant measuring duration and calculating lift after the lash was made up at tyhe lobe and .006 was added, this should  get closer to comparable duration measurements

So here is what I found, .016 lash / 1.76 rocker ratio = .009 lash at the tappet.  To compare the rated value of the hydraulic, I added .006 of rise Comp uses for the 270H.  So I measured duration at .015 to get comparable numbers at the tappet.  On the Bullet lobe, that measured 280.5 degrees at .006 tappet rise after lash makeup

Doing the same for the .050 (measured at .059) I got 230 degrees on the solid, compared to the hydraulic .050 of 224

Again at .209, to compare duration at .200, I got 140 degrees vice 132 for the hydraulic.

Finally, lift figures, when comparing .333 tappet lift less lash, I got .570 at the valve, vs .520 (The differences in rocker ratio are included in this)

So, in the end, Bullet claimed this was a Comp 282S copy, which indeed it is, however when you account for the lash, you actually get something much milder than you'd expect

Specs for the Bullet - 271 adv @ .020, 236 @ .050, 147 @ 200 and .333 lift  turns out to be much milder than you would expect

280.5 advertised at .006 tappet rise less lash, 230 @ .050, 140 @ .200 and .570 lift.

So here is the part to think about.  I measured all of these planning a .016 lash at the valve, Bullet actually specs out this lobe at .028 lash, and Comp 282S's are at .022.

If I were to lash it where Bullet wanted that intake lobe, that would require .016 lash at the tappet, plus the .006 to compare it to the hyd.  Which would have it under 270 degrees using this method,  .050 adjusted for lash would likely be very close to 224 degrees, and .200 duration would be very close to the 270's value.  In addition, that .333 lobe lift would be just barely over .550 at the valve

Something to think about, because although you'd have a bit more lift, and of course some benefit from solids at high RPM , essentially there isn't much difference in the hyd cam to the solid.

No surprise, because they say add 10 degrees for a similar solid to replace a hydraulic, but it's surprising when you do the measurement.  Essentially a 270H is closer to a 282S than you'd expect when you compensate for lash

[jayb]

I noticed the same thing when I swapped out the Performer RPM cam from my 428CJ, and put in a Comp 294S.  Duration at .050" numbers were 236/236 for the Performer RPM cam, and 248/249 for the Comp.  But on the dyno the numbers were nearly identical up to 5200 RPM, and the engine seemed to idle the same with both cams.  Of course the solid cam ran to a higher RPM than the hydraulic before it peaked in HP, but that was pretty much a function of the lifters.  So I'll bet you are right on comparing a 270H with a 282S...

[Mike Caruso]

Bullet/Ultra Dyne I have used cams designed by Harold B. since he was at General Kinetics, then Ultra Dyne, then Comp Cams. You can catch (Ultra Dyne Harold on Speed talk) these cams always are (act) bigger than the numbers. Check the lobe lifts on both cams @ .050", .100", .200" .300" it will give you a better picture since you don't have a Cam doctor.

I keep seeing people writing the hyd cams won't rpm? Puzzles me. Is anyone running Isky Anti-pump up hyd lifters? I used them for years BUT not for years LOL and would turn 7000 with out any problem at all. I would just call Richard @ Isky and ask him whats the deal on hi-rpm hyd lifters flat and rollers.

[My427stang]

Mike, I have talked to Harold quite a few times over the years, very helpful guy and certainly knowledgeable about power and valve train control.  I heard that he may be having health problems, he hasn't replied to any emails in quite a while.  I hope his is doing OK, may need to pick up the phone and see.

I generally map any cam I put in, and did here too.  Certainly no need for a Cam Doctor when we degree them any way, once set up is done, the measuring is the easy part. LOL  Honestly I doubt this is a UD/Harold lobe, despite being sold by Bullet, it just doesn't have his style on it.  It does accelerate a bit as it passes .200, but it's a pretty mellow lobe overall.

The key point was to show difference at the valve due to lash.  It can be significant in duration at the valve.  As far as the hyd comment, I have seen the same as Jay.  Although I have made them do OK with extra effort, running loose, fancy lifters, light components etc, anyone can slap 16 hunks of iron on a solid cam and do it easier.   So unless someone is class racing, or non-adjustable valve train, I don't see a reason to run hyd flat tappets if you want to spin it.

Hyd rollers, different story, they are popular and do well due to the threat of eating a lobe, but even then, if you want the big RPM, I'd go solid flat tappet or real big RPM solid roller

Now needless to say, this engine is not a high rpm machine, it may bump 5500 when I shift, but it's built to pull this truck around.

[jayb]

Mike, its not so much that hydraulic cams won't go to higher engine speeds, it is that you lose valvetrain control when you run them too high.  On the dyno you can see horsepower drop off significantly as a result.  The 428CJ dyno mule that I used for testing in my book was fitted with an Edelbrock Performer RPM hydraulic cam, and when the engine was installed in my Mach 1 I ran it to 6000+ RPM on a regular basis.  After I got my dyno, I pulled the engine and tested it, and found that horsepower peaked at 5300 RPM and then dropped off pretty dramatically afterwards.  I eventually got to the bottom of the problem by temporarily swapping in a set of solid lifters; then the engine ran with no horsepower drop-off up to 6000 RPM.

When I had that engine in the car nobody would have been able to convince me that it was losing power after 5300 RPM, because it seemed to run just fine to 6000 RPM.  But the dyno told the real story, and since it is not a good idea to lose control of the valvetrain, limiting the engine speed with hydraulics is probably a good idea.  With careful selection of components you can get more RPM out of a hydraulic cam; I've been able to get 6200 out of a hydraulic roller after some experimentation with spring rates and seat pressures, and I'm sure some people have done better than that.  But to me, the question is why bother; just going to solid lifters eliminates the problem.  Some people get concerned about having to adjust the lash on solid lifters, but with modern parts like a locking rocker adjuster it isn't required all that often; maybe once a year for a 4000 mile per year FE car.  Maybe not even that often.   

[Mike Caruso]

Guy's,
Thanks for the feed back and bringing me up to speed as to what you have been seeing. I hate driving a desk! But Dr's put a 4400 rpm chip in me LOL. I do know that it is the whole valve train that has to work happily or it will quit early like you two have found. New thought if you talk to HB please tell him I said hello.

Brothers of FE's

[blykins]

You can make them go, but it takes a good bit of effort and specialized parts....even more so with a hydraulic roller.