desk top dyno
 

i would like to see the curve on hp and torque of these two cams.
crane 168731
val. lift int 587 ex 610
adv dur 288/298 @ .050 226/236
lc 112
isky 696275/284 grind#rr275/284
val. lift int 553 ex 578
adv dur 275/284 @ .050 228/238
lc 112
motor is a zz502 9.6:1 comp alum head oval 110 cc
air gap intake edelbrock dual plane
holley carb 4150/4781-5 850 cfm
hei ignition (gm) (deg adv ?)
exh lightning header
I enderstand it wil be only bal park result thank you.

Re: desk top dyno
 

I'll run it for you this afternoon when I get home from work.

Re: desk top dyno
 

apreciated,i'll check result sometime tonight.

Re: desk top dyno
 

How acurate is a desk top dyno ?

Re: desk top dyno
 

My desk top dyno was real close to my actual dyno #'s. However, you need real good data to get accurate results from the program. You really need the flow #'s.

Re: desk top dyno
 

I just saw the software for 49 dollars. Does this sound correct ? If so its worth it .

Re: desk top dyno
 

Sorry it's taken me this long to get back with you but I just got home.
Please list the cam card info if you have it. DD requires the input of the cam timing events. Thanks.

Re: desk top dyno
 

I'm sorry i don't have the cam timming card.
wonder if anyone does ?
I'll do some researche and see what i can find,sorry about this!

Re: desk top dyno
 

Awesomerott,
Here are the head flow #'s for the GM aluminum oval heads. The far right # are exhaust w/pipe
0.2 138 119 86% 122
0.3 193 145 75% 156
0.4 233 168 72% 178
0.5 272 189 69% 194
0.6 299 202 68% 207
0.7 318 210 66% 213

Re: desk top dyno
 

Cam timing @ .004 for Crane 168731. I believe DD2000 asks for timing @ .006
Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 33.0 BTDC 75.0 ABDC 288 °
Exhaust 82.0 BBDC 36.0 ATDC 298 °
Bob

Re: desk top dyno
 

thank's for the #s.
what do you think of this DD,just curios.

Re: desk top dyno
 

were can i learn how to read these #'s and what it mean.

Re: desk top dyno
 

Isky rates adv dur for Hyd roller @.007 so trying to DD this with adv #,s will be invalid as valve events will not be comparable. Thats what leads to false output with these programs. Your only apples to apples would be the .050" numbers.
Isky 228*/238* 112*LSA 112*ICL
IVO 2* BTDC
IVC 46* ABDC
EVO 51* BBDC
EVC 7* ATDC
Crane 731 226*/236* 112*LSA 107* ICL
IVO 6* BTDC
IVC 40* ABDC
EVO 55* BBDC
EVC 1* ATDC
Keep in mind the Isky is straight up while the Crane is 5* adv. Changing your center lines will alter the valve events so use these as a baseline
Bob

Re: desk top dyno
 

If you advance the Isky numbers 5* they are nearly identical with the Crane
IVO 7* BTDC
IVC 41* ABDC
EVO 56* BBDC
EVC 2* ATDC
As you can see this is where the output on the computer sims gets very skewed, very quickly, many times without the user even knowing. Its been said that they are useful in predicting "trends" like peak TQ/HP placement, VE, etc but, in my opinion, I would never seriously consider component selection, especially camshaft profiles, based on the output.
Bob

Re: desk top dyno
 

bob i think i enderstand wath you mean about DD.
is there a simple way to explain how this motor would perform with these two cam ?

Re: desk top dyno
 

To clarify my last statement re; cam selection. Because there is not a set uniform standard for rating seat duration (a very important number), lobe area, accurate duration ratings @ .020/.100/.150/.200 etc your sims is really just giving a guesstimate at the actual lobe profile. Your very (expensive) advanced computer modeling programs utilize sophisticated cam measurement specifications in units of measurement in/deg at multiple points of lifter rise.

Re: desk top dyno
 

DD is a nice program to use when comparing parts from a baseline model. I like to use it and see how close the actual dyno results are.
rmbuilder, thanks for the cam specs. I appreciate it.

Re: desk top dyno
 

By examining 10 different intake lobes with the same duration in detail (example 280* seat duration intake lobe) with a CamDoctor program at multiple lifter rise points, it illustrates that single point references can be very generic, and that the 10 examined lobes can be very different from each other.
Bob

Re: desk top dyno
 

So unless you have extensive knowledge(like you and other) or expensive hardware,software it's very tuff to say wich one would work best when two cam profile are close.

Re: desk top dyno
 

Experience and knowledge base are important. In the case of the 2 very similar(duration) appearing lobe profiles you have inquired about the next step is to compare the lift figures(and requirements) which vary by about 10%, lobe intensity (rate of lifter rise), duration at .200", and lobe placement. Establish your valve events around your mechanical parameters, find the lobe that best fits within those events and you are much closer to an accurate choice.
Hope this helps
Bob

Re: desk top dyno
 

Sutphen30
They aren't especially forthcoming with that info (especially design information like lobe area). The end user doesn't ask for them and they aren't as "glamorous" as the head companies flow numbers.
Bob

Re: desk top dyno
 

Ok, here are some DD results.
Isky at 0 cam advance

rpm hp tq
3000 362 633
3500 422 633
4000 475 623
4500 519 606
5000 539 566
5500 531 507

Crane 731, installed at 0
3000 371 649
3500 430 644
4000 478 627
4500 510 595
5000 512 538
5500 494 472
I entered the cam timing event data as published by rmbuilder. Thanks, Bob.
If the cams are timed similarly (the 0 vs. 5 degree difference that rmbuilder pointed out) the numbers become virtually the same. Hope this helps you. Dave

Re: desk top dyno
 

By the way, I was fairly conservative on cylinder head selection in the Desktop Dyno program.

Re: desk top dyno
 

Dave,
Thanks for the good work you did on this! Post #9 has some accurate flow #s on those(390) heads if you want to enter them into your data base.
Bob

Re: desk top dyno
 

thank's guys, realy appreciate your inputs and work.
Dave what do you mean by numbers become virtualy the same ? outcome on DD the same ?

Bob, post #14,if you retard the crane of 5*,will it do the same,bring the crane #'s close to the isky #'s ?

Re: desk top dyno
 

Well,read the thread again and still have a hard time to pick between the two.
i don't have the knowledge to analyze all those theories and #'s.

Re: desk top dyno
 

I think what's confusing you is "the same"
What they mean is the HP/TQ curve are more down in the rpm range when a cam is advanced and up when it's retarded(backed off).One mfg quotes the "straight up"
figures one quotes the advanced. Since you can adjust these when installing it doesn't really matter which they use,just that you know and compare them with the same advance.Look at how the Crane makes more power down low on rpm. If you installed the Isky advanced like the crane its power would move down the rpm scale. It's ALL a compromise, like everything.

Re: desk top dyno
 

The other thing is,,if they are close you don't have to worry about picking because you will never be able to tell the diff between 520HP and 530HP.

Re: desk top dyno
 

thank's for the explanation Cooltoys.
something must happen today, some post missing from this morning.

Re: desk top dyno
 

I wonder if someone could answer my question on thread HP500 valve springs checked ok/engine builder did not changed ? post #18

Re: desk top dyno
 

If you want to compute the timing events based on duration and lobe center, it is quite simple.

Let's try a single pattern cam first. For a number lets try 250 degrees duration on 112 degree lobe separation installed with 112 intake centerline(meaning straight up,no advance or retard).

Divide 250 by 2 and subtract the lobe center(125-112) which equals 13. 13 is the intake opening event. Add 180 to that number and subtract the duration number again.(180+13-250) which equals 57. So intake opens at 13 btdc and closes at 57 abdc. Since it is a single pattern cam with no advance the cam specs will be as below.
Lets try a dual pattern camshaft of 250 intake and 260 exhaust on 112 LC "straight up"

To check your math, add the opening event and closing event then add 180 and it will equal the duration number.

Hope this helps :)

Re: desk top dyno
 

thank's Richard,it is simple.