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Cam comparisons

2K views 8 replies 5 participants last post by  zdld17 
#1 ·
Lets see if someone can tell me if they have seen the same trend I have been seeing here.
I am playing with the Desk Dyno and comparing hp and tq on a base 350 sbc.

One cam is a roller with 106 cl, 282/282 @ .50 & 510/520 lift,

Cam 2 is what the desktop dyno calls a Dual purpose flat tappet street, 109 cL, 282/282 @ .50 & 525/499 lift.

Cam one= 380 hp x 307 tq
Cam two= 438 x 354 tq

question is ,, why would the dual purpose street cam outperform the roller cam using the same engine components at 6500 rpm. This is a trend I see in several designs. I would think the roller with faster ramps would out perform the flat tappet. Even at lower rpm's the dual purpose is better . Is it the center lines?

Dave? JimM, Anyone?
 
#3 ·
pdq67 said:
First off, are you sure the numbers aren't advertised vs duration at .050" lift b/c 282 at .050" duration is one h-ll of a big cam!!

Then we can go from there.
OK,, thats 230/236 @ .050,, sorry bout dat. The 282/288 was at .006
DDyno will only let me input these only one way .
 
#4 ·
It has been proven that a solid lifter cam for the same lashed lift can knock a solid lifter open faster than darn near any of them EXCEPT for the full bore solid roller lifters!

Therefore your hy-roller/solid lifter cam comparo isn't quite as impressive as the soilid roller lifter cam should be, imho!!

I can see how a good aggressive solid lifter cam CAN out-power a hy-roller cam in this duration range easily, imho!!

Check my posts on I think here, Team Camaro AND Team Chevelle about me asking UDHarold to create a solid lifter equivanent to CC's GREAT 288AR solid street roller cam AND Harold did for me!!

(And btw, Harold designed the VooDoo cam line!!)...

AND, I'm gonna buy it off Harold for my 496 so I can make like 650 hp w/o using a solid roller cam and having to worry about the solid roller lifters going bad putzing around town....................

Here is Harold's e-mail back to me.

pdq67,

I've finally designed something, now I just have to make it......
A solid flat tappet replacement for the Comp Cams CB-288a-R10 their 11-692-8------
CB-288A-R10 288@.015 246@.050 158@.200 .622" valve lift 38-70-78-30
UDHarold's 285@.015 249@.050 161@.200 .618" valve lift 35-70-74-31

Their cam sells on their web site for $363.67, and the -8 in the part number means it IS NOT a steel billet. Lifters cost a good amount, too.
My cam will be a standard high-quality proferal cam--what solids have been made of for 30 years--and will cost around $168.75. Good Americian-made mechanical lifters are available at less than 25% the cost of solid roller lifters.
My cam stays .0176" away from the edge of the lifter, and I have had other cams that get closer to the edge go 100,000 miles on the street. The seating velocity is the same I have used on those 100,000 mile cams. Valve lash on mine is .018", on the Comp .020".
Because of changes in oil quality over the past 10 years, I would recommend using a lot of caution in breaking in ANY flat tappet solid or hydraulic cam.
The Comp Cams is symmetrical, mine, as always, is unsymmetrical. Look at the timing differences at .015"---My cam has a 4* longer power stroke, meaning more torque into your crank at ALL rpms, and a 3* later intake opening point, for less reversion and higher port velocities, again at ALL rpms.
At .050" and at .200", my cam is 3* fatter---Not only is it filling the cylinder faster, it has MORE time to do it.
The result---MORE POWER everywhere.
Now to get you guys some made......


Harold said it use’s Chevy solid lifters too!

UDHarold


pdq67
 
#5 ·
Don, way above my area of expertise...
but I could offer two observations.

First is I don't trust dyno programs worth a damn, garbage in garbage out and all that, it just seems they don't get enough info to properly spit out an accurate number. As in your example, 2 cams with near identical specs, but I bet if you saw a lobe off each and lay em on top of eachother they are VERY different.

My other observation is just the opposite, and more of a question. I've "shopped" a lot of cams, and it seems spec wise that hydro rollers seem very "tame" That is, even comparing a hydro roller to a hydro flat tappet, it seems that in a lot of cases, if the advertised duration is the same, the flat tappet cam will have a bigger number at .050, and pretty much the same lift.

Been really wondering about that. My pea brain would expect the roller to have both more duration at .050 and more lift that a flat tappet hydro with the same duration at .006. I don't really see that happening untill you get into some really BIG sticks.
 
#6 ·
First is I don't trust dyno programs worth a damn, garbage in garbage out and all that, it just seems they don't get enough info to properly spit out an accurate number
I agree...
Take 2 identical cams...the only diff being the rate of lift.
The one with the fast lift is great on the track and sucks on the street.
The one with a more gentle rate works great on the street and ok on the track.
Both in the same engine
There is far more to cams than just dialing basic specs into a program
 
#7 ·
OK ,, thanks to all , The comments pretty much sum up what trends I am seeing when comparing trash in / out methods. It also tells me you can spend more dollars on a cam that a $70 midnight special with data that inputs into desktop dyno or simuilar, and shows better hp / tq gains than the hi dollar cam does.
Jim I even compared your cam and on the desktop it seem to show better numbers. As for Harold,, he seems to want to improve much and I will certainly give him a chance on my next project. Appreciate the comments.
 
#8 · (Edited)
First in DD2k the "cam type" means NOTHING and has no effect on power numbers if you enter your own cam timing specs. HOWEVER, if you just change cam type it will put in generic cam timing for that type of typical cam profile (short duration for an "econo-street" grind, long duration for a "drag race" grind). If you do not go back and re-enter your duration specs you will be looking at power based a generic DD2k cam profile.

Second, lifter type is "code" for how agressive the lobes are. hydraulic flat tappet is least agressive and will show the least power for a given lift and duration, solid flat tappet in next in line and roller is max power regardless of whether the cam is a full on race grind solid roller or a mild street hydraulic roller It is dangerous to assume that this lifter type selection is a true representation of what would happen in an engine

For example: compare a state-of-the-art UD Harold hyd FT cam lobe with a comparable advertised duration old fashioned SSI solid FT. DD2k will have the old fashioned lazy solid ft cam making more power every time -- but we all know the truth ;)

Your results honestly look like there was a typo when you entered data. DD2k might have changed cam timing specs on you when you changed the "type" of cam and you didn't notice it.

Hope that helps!

Eric
 
#9 ·
No , No typo but I understand what your saying,, of course I have the older ddyno and all I do is change from my spec'd roller to the generic "dual purpose street" version and accept the .050 specs as generic as they look streetable . I think I have one other cam card on file some where on another motor, I will again enter it and I suspect el cheapo to our preform my hydra roller ,, on paper. These are just tools and best guesses IMO. I was just asking if others have seen the trend where the older versions of multipurpose or dual street cams out perform newer XE type cams. I do see some lobe center open up some by a 3 or 4 degrees, I did not think that it was a sole contributing factor. Thanks again.
 
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