Hi folks

I wonder if some guys that are strong on evaluating the relative merits of flow numbers could give me some feedback.

I have bought some AFR heads and I want to sell my current heads. I know very little on analysing head work and need help establish a value.

.200 128/121
.300 166/146
.400 211/168
.500 241/177
.550 244/181
.600 248/186

Barometer reading was 30.2 degrees. (whatever impact that has)

These are LT1 heads with LT4 valves. (2.00 hollow stem and 1.55 Sodium filled). They also have Crane dual springs.

Basically I'm trying to establish a value as "worked head" values seem to vary widely.

 

I'll catch you on the flipside of this... being that I'm notoriously long winded and have to run. This will at least bump ya to the top.

Take care,
Chuck Riddeck
Progressive Race Engine Development

 

TY Chuck

I was hoping you and SkadoroM could give me seme feed back

 

What's up Shaun? Check this link for some basic info.

http://www.fierolt1.com/lt1_lt4_headflow.htm

 

Was your sig performance done with those heads?

 

This is a tricky subject for sure. Simply due to the fact that there are so many variables at work here... test to test. Let me outline some of this before we get into our comparisons.

1) Flowbench calibration: Data is only useful for comparison when performed on an accurately calibrated flowbench.

2) Geometry: Alignment of the head with the bore-fixture must simulate the realationship the bore sees in the head when it is installed on it's dowels. This is an easy way to fluff up flow #s on a big valve high-lift head running on a small cylinder bore... move the intake valve away from the bore and you have a little less shrouding. Seen guys do it on purpose.

3) Need atmospheric conditions for data interpretation.

4) Need accurate lift readings

5) Was the head flown with the valves it will be using. You can also fluff up the numbers with a specially prepared valve. So you ask, "Why not run a valve with that geometry?" Because it wouldn't last a day under real operating conditions.

6) The head should be flown on a bore-fixture similiar to the actual bore of the application. This will have a greater affect on the big-valve high-lift heads than the smaller ones. Either way, look at the bore fixture diameter when making comparisons.

7) The head should be flown with a radiused inlet and an exhaust extension approximately 6" long. This will simulate flow more accurately thwarting shear effects.

That sums the biggest part of it up pretty well... I'm sure I'll want to add more to this the more I think on it but this should cover the bulk.

Now to comparisons... I haven't really studied this "Flow index" theory much... everyone has there little way of doing this. I was taught a method by David Reher when I worked at RMRE which I really like to use... it's somewhat quick and easy and gives a good idea of what we're looking for in a cylinder head.... area under the curve. Peak is nice but AUC is what wins races guys. So, let's cut to the chase.

I'll use two examples of similiar heads and keep it very simple for now...

The Brodix -10 (210 cc) in full port form #'s according to Brodix. 2.08/1.6 valves. (I'm only going to work the intake #'s here so we all get the basic idea)

Intake
@.200 --- 147
@.300 --- 205
@.400 --- 254
@.500 --- 287
@.600 --- 303
@.650 --- 305
@.700 --- 307

The AFR 210 cc "Racing Head", Competition Package (2.08/1.6 valves)

Intake
@.200 --- 138
@.300 --- 201
@.400 --- 247
@.500 --- 276
@.600 --- 288
@.650 --- 293
@.700 --- 297

Notice we used the same number of lift points. In practice, and in considering the application to be a daily driven street car, I wouldn't really use lift figures beyond the cam's maximum lift. We all know by now that the valve spends more time at low to mid lift... Reher use to say, "One time to peak and twice through mid lift".
For this example we'll use every lift point.
Now, here's the formula for calculating area under the curve (AUC):

AUC = .050 x (LP1 + LP1 + LP2 + LP2 + LP3 + LP3 + LP4 + LP4 + LP5 + LP5 + LP6 + LP6 + LP7 + LP7 + LP8)

May not make much sense in terms of the order of operations but it is easier for people to understane when written like so:

AUC = .050 x (LP1 + (LP1 + LP2) + (LP2 + LP3) + (LP3 + LP4) + (LP4 + LP5) + (LP5 + LP6) + (LP6 + LP7) + (LP7 + LP8))

So, work through the lift points of the Brodix -10 and you get a AUC value of 166, do the same for the AFR and we get 159

Brod -10 = 166
AFR 210 = 159

Notice we used all the lift points in this example. Now let's look at the Brodix Smokey Yunick head as prepared by Weld Tech. For this example we're only going to look at #'s to .500 lift. Our comparison will be to the AFR 210. Important to remember here is that the AFR 210 is cast to 210 ccs, it is then worked to flow what it does in it's "Competition Package" form... in other words, the port volume is greater than 210 ccs in finished form.
The Brodix SY head on the other hand is finished by Weld Tech to 187 ccs and uses a smaller 2.02/1.6 valve combination. Now let's look at the numbers...

Brodix SY Intake:
@.200 --- 142
@.300 --- 204
@.400 --- 251
@.500 --- 254

AFR 210 Intake:
@.200 --- 138
@.300 --- 201
@.400 --- 247
@.500 --- 276

Well the AFR won, it's got the bigger peak # right? Do the math....

Brodix SY:
AUC = 72.4

AFR 210:
AUC = 72.4

(BTW- I went through the math real quick so please double check)

A little more to flow numbers than peak. The SY appears to be at a disadvantage, it has a smaller port volume and smaller valves, yet it would walk off and leave the AFR 210 in similiar applications.... In this case let's say a 3 speed auto car that weight 3700 lbs, using a mild cam and using a numerically low rear cog ratio.

This is only a smidge, but it should broaden your understanding of what really matters when looking at cylinder heads. Didn't directly answer your question but hopefully you got a little more bang for your buck with this explanation.

Take care,
Chuck Riddeck
Progressive Race Engine Development

 

Yes they were. However, the HP numbers in my sig were restricted by a restricted fuel system. i was running extremely lean as fuel was not getting to the rail. i'm currently installing a new dual pump intank system and have bought dome AFRS's

Chuck: WOW. That is fabulous info. I should add that i have a whole bunch of other info on the results sheet I got whch meant nothing to me but I think they is some of the info you allude too, angles etc. there is also another column of numbers but I did not know what they meant.

It seems to me that I have a "stage 1" port job. Does that sound right?

 

Chuck,

that's a really cool way to do that!

On engines I have done and I had 4 sets of heads to choose from I did some other math. I don't have the spreadsheet any more but it was basically a comparison between the Brodix Weld Tech Track 1's, the AFR 215cc CNC ported ones, the Edelbrock #61209 CNC ported Chapmans and another CNC set, I think the 220cc Pro CNC heads.

Anyways these heads were the choices due to the flow numbers they produced and the runner volume range.

The Brodix was the smallest @ 215, The AFR was actually 235cc, the Edelbrock was 236cc's and the Pro's were alot larger. Basically it took the flow at lifts from .200 to .600 and divided that average by the cc's to give me a average flow per cc. That came up with the Brodix with the smallest port and 2nd or 3rd best flow as the winner due to the fact that it had the best combo of size and flow for the engine displacement and the rpm range is was to be run in, along with the HP level. I think i'll use your formula in that now to add a better way to do it. Race engines and street engines need the right port sizes for better power in the RPM curve.


Your right about those SY heads, for the size they are killer heads. Port velocity of them over the larger heads will make them a much better head. If you were going to 8000rpm they would probably have too small of a cross sectional area and get choked off.

I like what you do down there. You don't need anyone else do you?

Bret

 

Could some one pitch in with their thoughts on the value of these heads to sell?

 

can't tell you there. The value would have to be less than a better flowing one.

here is a link to TEA's LT1 heads

That is $1500 so you are not up to that so I would say $1000 would be good.

Just my thought.

Seems like with $300 heads and parts $600 is not worth it in work to me.

Bret