Another "How much will it make?" Project "Special Needs"

[sjre]

cgt and randy , randy you suggested the cam on a 112 you chose a 110+ 4 what changed ?Also You like ivc @ 40-45 on this size engine what if it were a 496 bbc. Would it stay the same if it was to peak 6500 or would it be later like 50to 55.In other words does ivc or evo vary as cubes increase or stay basically in the same area ? Also what about the seat duration not just 050.I have seen cams that should have peaked higher but didnt,even with good flowing heads, was it the evo not the intake duration hurting?
thank you

[randy331]

There seems to be a lot of interest in the flowZ of the heads going on this "Special Needs" engine.

Intake
lift-----cfm
.050----36
.100----67
.150----76
.200---123
.300---184
.400---236
.500---267
.600---288
.650---291

EX.
.050----18
.100----38
.150----60
.200----97
.300---133
.400---176
.500---200
.600---209_W/pipe 230
.650---211_W/pipe 232

2.08" intake valve-1.55" ex valve 50* seats on both.

Been bust workin on my new shop/house and Ain't had much time for posting FlowZ.

Randy

[randy331]

I don't know if you plan on posting the flowz or not but do you happen to have the Cd at .100 for each valve?

FlowZ are posted!!

I show a window area of .426 sq in. for the intake at .100" lift.

The EX. is .315" sq in window area at .100" lift.

Randy

[RevTheory]

FlowZ!

If I've done my math right, I'm showing a Cd of 30.8% and 23.6%. Based on that, I'd be extremely inclined to have that cam on a 106 +4 or maybe even an earlier ICL.

I've never had to pick an exhaust lobe where most of the numbers were done without a pipe but a couple were done with a pipe. If the gains carry through the curve like they do at .600, I doubt if I'd have more than a 4* split but the low Cd makes me want to stretch those events out further than I normally would. I'm thinking about the exhaust blow-down phase and signal transfer across the chamber during overlap here.

I'd probably be looking for something along the lines of Comp QXI on the intake: 289/237 at .050, .632 valve lift and Comp QXX exhaust: 301/247 at .050, .581 valve lift.

IVO- 16.5 IVC- 40.5
EVO- 53.5 EVC- 13.5

I know that sounds like a lot of duration but the valves aren't really doing anything at low lift anyways.

Let the beatings begin...

[randy331]

FlowZ!

If I've done my math right, I'm showing a Cd of 30.8% and 23.6%.

30.8% and 23.6% of what?

Your saying the intake is at a 30.8% CD of the window area at .100" lift and the EX. is at 23.6% at .100" lift?

Randy

[RevTheory]

30.8% and 23.6% of what?

Your saying the intake is at a 30.8% CD of the window area at .100" lift and the EX. is at 23.6% at .100" lift?

Randy

Of what a perfect tube of that area should theoretically flow. If I've got my math or definition wrong, I'm all ears. We're all here to learn, right?

[randy331]

I guess I'm in the dark.

I come up with a .426 csa flowing 67 cfm as being 157 cfm per square inch of area, and your saying that's 30.8% of what's possible?

Randy

[RevTheory]

I guess I'm in the dark...


Randy

Probably not. I gave it some fresh eyes this morning and nothing looks right. Not the calculator, the input variables, the result... nothing. I'm going to sit on my hands until I get it straightened out.

Hey, you're the cylinder head guy. I should be able to ask you what the Cd is

[randy331]

Hey, you're the cylinder head guy. I should be able to ask you what the Cd is

I tend to just call out cfm/sq in, instead of using a DC. Everyone would need to be using the same ideal, or 100% before DC means anything.

At .100 lift the "DC" or CFM per sq inch of area will be high on most every head. At .100" lift the port isn't a restriction, nothing is too close in the chamber to limit flow through one side of the window, the top angle and valve margin achieve good pressure recovery all the way around the valve.

It's interesting to compare the actual window area (not diameter x pi. x lift) of a 50*/55* valve job VS a 45*. The steeper valve jobs always flow less down at .100-.200 lift, but it's almost always at a higher CFM/sq. in.

And who promoted me to cylinder head guy? I'm just a part time Hobbyist.

Randy

[RevTheory]

I talked to a buddy last night who's strong in The Force and we determined that whether or not the math was correct (and I don't believe it is), it was the wrong way to compare apples and oranges. It could be useful in comparing two seat designs on the same diameter valve but not a 2.02/45* vs a 2.08/50* combo.

He went through a bunch of printouts and figured there wasn't really a need to tighten up more than the 108 LSA I originally thought. He liked the intake lobe I picked but thought the exhaust was pretty excessive- I agree now.

Anyways, my bad...

[CGT]

Thanks Rev, for allowing "The Force" into my "Special Needs" project!

[RevTheory]

Good with flowZ and camZ, he is. Willing to help, he was.

[randy331]

May " The Force " and the flowZ be with "Special needs " in it'z quest for power!!

Randy

[CGT]

Maybe if dyno time and fundz permit. I will try a 2nd....very different cam?

[randy331]

It could be useful in comparing two seat designs on the same diameter valve but not a 2.02/45* vs a 2.08/50* combo.

I thought this an interesting comparison of a 2.02" 45* valve job vs a 2.08" 50* valve job.
I used a spread sheet done by rick360. It figures minimum window area, and includes the affects of valve back cuts, top cuts in the chamber etc.
Left column is lift, and under each valve/angle description is the actual window area in sq inches.

lift...2.08/50*---.2.02" 45*
.100---.426--------.459
.200---.928--------.975
.300---1.461------1.504
.400---2.046------2.075
.500---2.648------2.661
.600---3.258------3.254

At .550" lift both have the same window CSA, but by that lift the throat is going to become smaller than the window area, and on some ports there will be an even smaller minimum CSA up stream. ( like the pushrod )

So if DC is part of specing camz, shouldn't we know the true/actual window CSA?

Even if we completely ignore DC and just use flowz only, shouldn't we know what the flowz are with the intake on, with the actual header/ex system to be used?

Maybe if dyno time and fundz permit. I will try a 2nd....very different cam?

Like what?

May the flowZ be with all the ST members this holiday season.

Randy