head flow vs cam choice

[UDHarold]

Guys,

Someone has several carts before the horse.
We change LSAs to affect the desired power curve.
Pro-Stocks run 114-120 LSAs because they are concerned with the shape of the power curve from 8000 to 10,500.
The old 1980s-era Super Stocker had a cylinder head that didn't flow much past ,550"(SBC), and to be competitive, you had to use a short cam with about .660"-.700" at the valve. The LSAs on 102-104 were to give a tremendous hole-shot at 5000 with those limited heads.
As porting rules change, and converters improve, LSAs have changed also. Now wider LSAs are in use, for the same engine as earlier.
LSAs change as what you want to accomplish with a cam changes.
Tighter LSA=more mid-range, or crutch a too-big port.
Wider LSA=wider power curve, and for high-velocity ports.

UDHarold

[CamKing]

LSAs change as what you want to accomplish with a cam changes.
Tighter LSA=more mid-range, or crutch a too-big port.
Wider LSA=wider power curve, and for high-velocity ports.

Harold, if we keep agreeing, what are we going to argue about?

[CamKing]

If someone knows him or his email address, maybe we could invite him here to explain his point of view? (I wouldn't mind learning)

Heck, I could just drop by his home for lunch.
I know David pretty well. He doesn't have any more crazy ideas then I do, I just don't print mine.

[Stan Weiss]

If someone knows him or his email address, maybe we could invite him here to explain his point of view? (I wouldn't mind learning)

I have his email address and I sent him an e-mail about this. But if this is like other e-mail I have sent him it will take sometime for him to get to it because of all the e-mail he gets. There are times I get the answer to my email when I call him on the phone. You can try asking him here. http://www.gofastnews.com/board/

[SStrokerAce]

You tighten up the lobe centers when you have too big of a port, and widen them when the port is too small.

So I guess a Pro Stock motors ports are too small with 118+LSA?

I'm suprised that not one person here has realized any link with LSA and the harmonic tuing aspects of the motors, along with RPM. Higher the amplitude of the tuing wave pressures the later you can close the valve... wonder what that does to LSA?

Might want to think about that relative to PS motors and SS motors and the relative LSA's and the ability for each of those motors to propigate strong wave amplitude in the induction system. I guess formulas developed in the 70's and 80's to design cams only care about port area, not length. That explains a lot right there.

Big Port, Small Port relative to LSA is bunk IMHO.

Bret

[EDC]

* subscribing *

[UDHarold]

Brett,

For 27 years I have had in print that my cams utilize Inertia Ram in filling the cylinder, and that I close the intake valve later, because of the cam's unsymmetricallness.
I seem to have been using this all along.
However, if you would like to buy a cam from CCC, I will be able to convince them to make you one for a 500 CID Pro-Stock on a 108 LSA.
Please let us all see the dyno-curve when you're through.
I think I should have called them "High-Velocity Ports" instead.

UDHarold

[jmarkaudio]

After all of this, I still come up with the following:
There is a perfect cam for every engine/vehicle/RPM range combination. If you change ANYTHING of significance in that combo, the cam requirements change. Maybe not much, or noticeable depending on the change, but a change none the less. Computers can get us close, but still not able to completely simulate real world conditions. Then you add the human factor...

[CamKing]

After all of this, I still come up with the following:
There is a perfect cam for every engine/vehicle/RPM range combination. If you change ANYTHING of significance in that combo, the cam requirements change. Maybe not much, or noticeable depending on the change, but a change none the less. Computers can get us close, but still not able to completely simulate real world conditions. Then you add the human factor...

You nailed it.
You may want to try and explain it to the SStrokers of the world.

[CamKing]

You tighten up the lobe centers when you have too big of a port, and widen them when the port is too small.

So I guess a Pro Stock motors ports are too small with 118+LSA?

The thing your mind doesn't grasp is that 118 may be a tight lobe center for a Pro Stock application.

There are many factors involved with calculating the correct lobe centers.
Changing the port velocity will only move it tighter or wider from that point.

BTW, I just did a Pro Stock cam for a new port design, and I tightened it up to 117.

I did cams for an Indy project a few years ago where they filled in the intake runners, and I was able to widen the lobe center all the way out to 104.

[Joe Mendelis]

I guess the guys who make power sell cams/heads to peoplen that will buy them again.
People who's stuff Doesn't run ends up on the shelf or in a pile on the dyno room floor

[SStrokerAce]

Actually I shouldn't have even used LSA in my first post it should have been centerlines and more appropriatly ICL. I have some odd thoughts on camshafts that differ with other guys out there. I'm much more intested in getting the valve events correct and the reasons WHY they work and don't, than I am about lobe designs. I give you guys a lot of credit in that area, but really think it is over emphisized to a point. I've seen more cams have the perfect lobe for the application, giving great valve control but falling short in terms of optimum average power output due to having the wrong valve events.

Brett,

For 27 years I have had in print that my cams utilize Inertia Ram in filling the cylinder, and that I close the intake valve later, because of the cam's unsymmetricallness.
I seem to have been using this all along.
However, if you would like to buy a cam from CCC, I will be able to convince them to make you one for a 500 CID Pro-Stock on a 108 LSA.
Please let us all see the dyno-curve when you're through.
I think I should have called them "High-Velocity Ports" instead.

UDHarold

Harold,

That wasn't aimed at you. From your posts it's obvious you grasp this concept, i'm just throwing my spin as to why something yu have done for years works.

As for the 108LSA PS cam, I think I will pass. Then again you probably wouldn't want to put your name on that either.


Mike Jones,

Some of the stuff you write on here is on the money, but it's too bad when someone differs or takes it up a notch to what you have said you get all hostile. Take that rocker arm arguement lately, jesus that one was bad.

I'm seriously wondering how close the motors are to optimum when you can decrease cross sectional areas of these heads so much that it helps. They must be some really dialed in motors

I reeeeaallly want to hear this explaination of how port velocity is the ONE thing that changes LSA. Are you keeping the CSA the same when you are doing this? Either way explain this one too me? Is it the velocity or the CSA that makes the difference? Is it both, is it one or the other? Also I'd like some explaination of WHY?

I'll tell you my opinion that it's grossly simple to think it is one thing at all, especially since you can't have velocity without flow, and without pressure differences you don't have flow. In the end it DOES come down to pressure no matter what you say, or even in this case you do agree you just don't get that you do. You just can't stand somone pointing out that how you think about it has some serious holes in your theory. That's what blows my mind about engines and those of us who work on them, panties get in a bunch in a big hurry when someone tells someone else that their theory as to WHY something does what it does is off. Maybe that's why we all work on something that at it's best is about 35% efficent.

Bret

[CamKing]

Mike Jones,

Some of the stuff you write on here is on the money, but it's too bad when someone differs or takes it up a notch to what you have said you get all hostile.

Harold and I differ on opinions all the time, but we both respect each others accomplishments.

I just have a problem with B.S.'ers.
You lost all credibility with me with your Daytona Prototype claims.

You're welcome to have all the theories you want, but until you actually prove them, they're just your opinion. Go out and design a cam, manufacture it, put it in an engine, dyno it, and go out and win a championship or two hundred.

[EDC]

Cripe... This got nasty fast!

[stumpy]

Interesting stuff!