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

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

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

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

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 ?

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.

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.

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.

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

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