Flow vs hp

[Diodedog]

..
There's zero relationship between the 2 CFMs.

So flow benches are a complete waste of money?

Not a complete waste of money but they do not predict the future. Kaase had a nice article a while back on Hemi vs. Wedge heads. It is worth a read or two. Basically his two heads flow roughly the same on the flow bench but the Hemi head makes a lot more power on an engine. So the flow number tells you part of the story, but it doesn't tell you the whole story. There is a quality of the flow which is important. Also the location of the flow, and the velocity of the flow. I'm sure there are other things such as turbulence and swirl and who knows what else.

All of the info is in the Superflow owners manual.

[mag2555]

By flow testing even putting cfm totally aside and just velocity mapping the whole port top to bottom and end to end at .050" lift steps WITH the Manifold attached is where flow bench testing shines!!

[swampbuggy]

X2 Mag

[Newold1]

The old saying comes to mind: "A LITTLE KNOWLEDGE IS A DANGEROUS THING!"

The tech article by Darin Morgan in a previous post should be required reading as a start for all those of us on Speedtalk except for a few cylinder head experts before we start throwing around the single concept of CFM air flow as tested in various cylinder heads.

The more we learn and realize about induction path performance in an engine the more we see that all internal combustion engines produce power as a system and single determination factors can not and should not be the single determiner of how an engine is equipped or specific parts are chosen and modified. iT'S JUST A PART OF THE PLAN.

We all are guilty sometimes of just putting to much importance on a single factor like a CFM flow number and making a blanket determination that this can be equated to a specific horsepower number out of a particular build. As the experts show and tell us "IT AIN'T THAT EASY"

[Steve.k]

Ok has anyone got flow on these over 400? Is that doable?My flow bench guy says he thinks it be a stretch. One local shop has a set of gliddens old heads may see if he would like to flow.

[rustbucket79]

Sure. I know I cam make over 1000hp with 380 cfm, like 1020, and its not a basic build. To find 80hp, it would be tough, but not without more head work. Like Andy said, a lot more to making horsepower than flow numbers. The other thing, people get funny when I bring this up, but there ABSOLUTELY are happy dyno's out there, period, end of story, I don't care what anyone says. I know shops f%ck with the numbers, lots of stories. The engine above, take it off the dyno I use, that performance more than matches the numbers, take it 40 miles to the east, just across the border, and it would absolutely be an 1100hp engine. On average, the 10-12 examples, that have been run at both shops that I know of, make a bit over 10% more everytime. So which is it, 1000hp or 1100hp? Its on a sheet of paper after all.

I know all to well what you're saying. Put two different well known American engine shops SR20 engines on our dyno, they were supposed to make 1200+, both made in the area of 1070 in our shop, guess it's from the conversion from imperial to metric.

[MadBill]

..
There's zero relationship between the 2 CFMs.

So flow benches are a complete waste of money?

Not a complete waste of money but they do not predict the future. Kaase had a nice article a while back on Hemi vs. Wedge heads. It is worth a read or two. Basically his two heads flow roughly the same on the flow bench but the Hemi head makes a lot more power on an engine. So the flow number tells you part of the story, but it doesn't tell you the whole story. There is a quality of the flow which is important. Also the location of the flow, and the velocity of the flow. I'm sure there are other things such as turbulence and swirl and who knows what else.

Quite so. Also, it's pretty hard on a flow bench to simulate flow at TDC +/- 40°, where the flow in a high dome parallel valve engine would surely suffer vs. that of a Hemi with a trench-style dome relief...

[Steve.k]

Very interesting articl of Morgan's to say the least. That added a whole new dimension to this project. I guess we do more research,collect some parts and see how close we get.

[Newold1]

Steve.K glad you read Darin's article as Darin as many know has forgotten more about cylinder head design, flows and performance than most of us even know combined! It is really important to look at a lot of areas and information before we just focus on a limited number of engine build specifics. It becomes more apparent as one studies the math, science and the interaction between all the systems involved that carefully putting together a great engine build that it is really a moving target and most of the time a sometimes difficult result to predict or deliver. For those of us who do it more often we know, if we are humble, that its' PRACTICE, PRACTICE, PRACTICE!

[digger]

..
There's zero relationship between the 2 CFMs.

So flow benches are a complete waste of money?

Not a complete waste of money but they do not predict the future. Kaase had a nice article a while back on Hemi vs. Wedge heads. It is worth a read or two. Basically his two heads flow roughly the same on the flow bench but the Hemi head makes a lot more power on an engine. So the flow number tells you part of the story, but it doesn't tell you the whole story. There is a quality of the flow which is important. Also the location of the flow, and the velocity of the flow. I'm sure there are other things such as turbulence and swirl and who knows what else.

The two heads tested would need vastly different exhaust cam characteristics so it's hard to get much from that test imo

[GARY C]

This would be along the lines of Australian Pro Stock small blocks, they are 435 cfm and over 1100 at 400 ci.
viewtopic.php?f=1&t=28533
viewtopic.php?f=15&t=31234

[Steve.k]

At the very least we will shoot for the highest hp iron cleveland.

[Mark O'Neal]

The problem is that it's a shifting number. At the turn of the century, the rule was that it took 410 cfm to make 900+. Then cams changed, pistons changed, rings changed, valvetrain changed, and we have to come up with a whole new set of rules.

I hate it when my cat helps me type.

[Mark O'Neal]

And, it would be nice if everyone flowed at a standard bore size.

[andyf]

Here is a 514 inch Mopar big block with Indy EZ heads. The EZ heads are the bottom of the list at Indy, basically a street head. They flow in the 350 to 360 range depending on what bench and what bore size you test them on. Engine makes right at 900 hp with EFI on a cast single 4bbl intake. Cam isn't huge, 282/288 duration. 2 inch dyno headers. So not exactly a Pro Stock engine. You can see the data on the dyno console, correction factor was 1.02 so this isn't one of the dyno tests where the correction factor is 20% or something like that.

https://www.youtube.com/watch?v=LZcFl7fy6FI