Making sense of old flow numbers.

[mag2555]

So I was going through old magazines that I have to toss or keep them.

One I was Thumbing through was from 1971.
It’s by Petersens and titled Basic cam’s valves and exh systems.

In it is a article on air flow testing.
One thing covered is the work that Warren Brownfield was doing on his flow bench that he made.

The article references numbers he was getting from the work he did on a SBC 327 head.

They posted before and after numbers and here they are, but even when you try to make sense of them in terms of percentages I can’t .

For example, at .250” lift the flow gain is 69.5%.

Now the article is not clear if these numbers where in reference to the intake or exh side, but to me either way they don’t seem 100% possible, especially in the low lift ranges.

Your thoughts?

[swampbuggy]

The reworked numbers are Impossible if the testing was done under the conditions commonly used today . Mark H.

[mag2555]

I wish there was a reference to a test depression being used.

[BOOT]

There must be some kind of typo error or other...

[dannobee]

If the referenced "327 FI head" is assumed to be a stock 461 or 462, we know that those flow ~210 cfm @ 28" H2O.

[hoffman900]

The type of flowbench, its design, leaks, construction, etc. all effect it.

We know you can’t compare numbers from a floating depression flow bench to a static bench like a Superflow. Different designs will calibrate / scale differently.

It’s like a dyno, and honestly you should only be comparing against your own.

[PRH]

It’s like a dyno, and honestly you should only be comparing against your own.

I agree.

Here are numbers from a head tested on two different benches.
It’s the same head, same port, same valve, tested on two of the same make & model bench(Saenz S-600).

Intake flow(same port, same head):
Lift———A———B
.200— 163—— 138
.300— 220—— 199
.400— 270—— 249
.500— 319—— 290
.600— 347—— 333
.650— 336—— 346
.700— 334—— 329

Exhaust:
Lift———A———B
.200— 124—— 101
.300— 169—— 139
.400— 210—— 177
.500— 242—— 211
.600— 265—— 237
.650— 273—— 244
.700— 275—— 253

[mag2555]

Ok fine I understand all that , but Brownfield’s results I have posted about here where on his very same bench’ just before and after the rework he did.

I’am comparing his numbers to his numbers.

I am leaning towards the fact that it must have been a floating depression bench.

[PRH]

I think you’ll be hard pressed to find any flow tests on a factory SBC double bump head from the last 20 years, done on modern equipment, where the improvement from the rework @.200 lift is 82%.
(Not to mention the 100%+ gain @.100)

Taken at face value, his numbers can be compared to his numbers.
Trying to correlate them to any other numbers is, imo, an exercise in futility.

[HQM383]

It’s like a dyno, and honestly you should only be comparing against your own.

I agree.

Here are numbers from a head tested on two different benches.
It’s the same head, same port, same valve, tested on two of the same make & model bench(Saenz S-600).

Intake flow(same port, same head):
Lift———A———B
.200— 163—— 138
.300— 220—— 199
.400— 270—— 249
.500— 319—— 290
.600— 347—— 333
.650— 336—— 346
.700— 334—— 329

Exhaust:
Lift———A———B
.200— 124—— 101
.300— 169—— 139
.400— 210—— 177
.500— 242—— 211
.600— 265—— 237
.650— 273—— 244
.700— 275—— 253

Wow.

Hypothetically if a diy guy took said head to person with bench A for baseline, went home and done a bit of rubbing, then bench A guy was busy so bench B guy is used to check progress then some grinding tools could be up for sale on marketplace.

[rebelrouser]

Ok fine I understand all that , but Brownfield’s results I have posted about here where on his very same bench’ just before and after the rework he did.

I’am comparing his numbers to his numbers.

I am leaning towards the fact that it must have been a floating depression bench.

In comparing his numbers he made a 22% increase in flow at .550 lift. That is not out of line. As mentioned, flow benches all read different. I have a homemade bench and it from looking at a lot of heads and numbers is pretty close on the exhaust side and a little generous on the intake side, I don't worry about it because I flow the heads before I start work for a baseline, and then go on from there. 15% to 25% improvement on a set of stock iron heads is a good port job from my experience. On newer aftermarket heads 10% to 15% is a good result. At least for me anyway, others may be more talented.