shaggy56

Here is something interesting to look at when looking at flow numbers. Lots of folks base buying heads on flow numbers and this is something to think about when looking at heads.

In the DM series they tested the E-Tec's and Air gap against the Brodix RR 180's and HVH. Both with a Hydraulic roller 234/238@.050 .574/.584 w/Comp 1.6 rockers. Every flow chart will show the Brodix heads outflowing the E-tecs but take a look at these dyno results.

E-Tecs RR 180

RPM TQ HP TQ HP
3000 403 231 373 213
4000 444 338 400 305
5000 458 436 424 404
6000 425 485 408 466

Peak 458 486 425 469

Air_Adam

Aren't E-Tecs 200cc?

It hardly seems fair to compare a 180cc head to a 200cc head.

grumpyvette

that test may be interesting....but far from valid unless all the components used are listed AND UNDERSTOOD as to their EFFECT on the total combo. you may also be forgetting that the other components like the engines displacement,compression ratio,intake manifold sellected,header primairy length and dia. ETC. DO effect the results.
its NOT only the port flow numbers but the above listed factors (and others)and the CROSS SECTIONAL AREA that effect the ports flow velocity,and volumetric efficiency.
both heads can EASILY be shown to be superior to the other useing dyno results,by varying the other factors in the combo

Dialed_In

iTrader: (3)

We had a 432 we were building and couldn't convince the customer to buy another set of heads. He had a set of Edelbrock Victor Jr's. We ended up going all the way through them, ported the intake and exhaust, went through the chambers, valve job, yadda yadda yadda. Ended up flowing something stupid like 280 but the motor made 658hp/690 tq and the car runs 8.80's. The bench is just like a dyno, it's a tool. People who use it otherwise have some learning to do. We use it mostly to see differences when we make a change to a head. Comparing different valve angles to see what will work and so on. Aslo don't forget that the charachteristics of air flow change drastically when you add fuel to the mix, and not too many people have a wet-flow bench.




Not to mention that everyone tests with different parameters and that every flow bench is different. There are lots of variables and no industry standard which means when you're looking at flow numbers there are a lot of things you have to ask yourself.

a.) on the intake side, what is on the entry? Is it clay, a radiused entry or an actual intake manifold? Example, lots of shops flow LS1 heads with a radiused entry. Well this is WRONG. When the head is on the motor and the intake is bolted up, the top part of the port is filled by the injector and injector boss on the intake. Now your 300 cfm head is now a 250 cfm head.

b.) Is the exhaust being flowed with a pipe? What size?

c.) What bore size is it being flowed on?

d.) What pressure are they flowing the head at? This is the only standard in the industry and is usually 28 in/h20 but it's not hard to crank it on up an inflate the flow numbers.

e.) Weather affects the results too. Just like the air going into a running motor the air going through a flow bench is affected by temperature and humidity and thus the results should be corrected. (unless you're comparing a number of heads on the same day with the same conditions).

f.) The person doing the test also needs to make sure that the pressure of the bench isn't sucking the valves open. See this all the time. When doing a flow test you use low tensions springs just enough to hold the valve in the head. Well this makes it very easy for the air flowing through the chamber to actually suck one of the valves open. If this happens it's very unlikely that you'll notice it during a flow test.

shaggy56

This test was with the 170's. It is in Super Chevy's "Danger Mouse" series. The issues were Nov 04, Dec 04, and Jan 05. They did the e-tec 200's first, then the e-tec 170's, and then the Brodix RR180's. All with the same cam but different intakes and the 170's beat them all. The motor was a 355. I think the point is to match components rather than look for the best possible flowing heads.

kdrolt

Who would have thought there would be that much of a difference between them (powerwise) given that they both used small-runner heads. There isn't any glaring mismatch of parts in the test, and the results were actually very good for both.... it's just that one looks much better than the other. Matching the components would be hard to do unless you had a lot of data to learn from.

This excludes avoiding obvious bad-matching parts, like 220 cc intake port heads with a stock factory cam.

That said, what was the ignition timing for both tests?

Without knowing the answer I'd guess that the heads that flowed less, but made more power, did it because they're more efficient & faster burners of fuel. The telltale would be less ignition timing. Say (I'm guessing) 30 deg for the Etecs and 36 deg for the Brodix.

AJ_92RS

A high flowing intake port doesn’t have to be big. A low flowing intake port doesn’t mean it’s small. The main goal is to get the most flow through the smallest port possible to increase efficiency. That's what the Vortec design accomplishes.

Other tests have been done to show that in some engines a smaller cam will make more HP and TQ throughout the entire RPM range including peak numbers. That doesn’t mean everyone is running too big of a cam, albeit a lot of people are.