AFR Heads

Newbomb Turk said
Nope. You know, if you go to the Reher-Morrison website you’ll find a number of tech articles written by Reher. He covers this in one of those articles.

There may be more than one in which he covers flow numbers.

I’ll give you an example. You have two “identical” heads that both flow 300 CFM. One makes more power. Why is that?

Because there are things that bulk flow don’t tell you.

You can blindfold me and do a flow test and I’ll tell you the instant the port goes chaotic. You don’t see that on a piece of paper with flow numbers on it.

You can’t tell by flow numbers which port will deliver the best quality air flow.

Unless you are standing there, doing the test you have no idea what the port sounds like. Sound is critical. Darin Morgan has talked about this.

Never trust flow numbers when you do the math like PRH did and the flow numbers are impossible.

Same for dyno numbers. If you aren’t looking at fuel flow you have no idea if the numbers are correct or not.

When the rpm rule in Pro Stock came down and the Dodge couldn’t get out of it own way, Chris McGaha put a Dodge on his pump.

He knew by looking at the fuel flow numbers it wouldn’t make the power it needed to at the rpm NHRA mandated.

NHRA knew it when they made the rule and did it anyway.

I got kicked off yellowbullet for calling out a Pro Stock engine builder who couldn’t make a Dodge run with a gun to his head.

He said the rpm rule would save big money and save Pro Stock. I called him an idiot. He was wrong. It killed the Dodge and the Ford guys knew it did them in too. Once again, GM bought the rule book and pencil shipped the competition right out of the game.

And McGaha did an interview or maybe an op-ed and he said a year or so later what I knew when the rule came out.

It wasn’t rpm that was killing the class. It was the cost of crew travel and missed time back at the shop.

Sponsorship money was next to nothing. Payouts are a joke. Flying in a crew, housing and feeding them plus the lost time at the shop is the real killer.

The idiot engine builder should have known that since he had a front row seat to the whole **** show.

TLDR; flow numbers will lie to you. Don’t buy a head based on flow numbers.

I get what your saying and agree with the premise but when you look at builds of certain levels cam, cr, etc.. and look at the hp and head flow the hp per cfm is generally in close range of one another somethimes you'll see one that surprises you. When you hear Darin Morgan talk about hp per cfm I hear him generally give is 2.4-2.5 hp per cfm causes that's the world he lives in. Most street/strip engines don't seem to make even 2 hp per cfm from what I've notice they seem to fall in the 1.7-1.9 hp per cfm, does that mean your guaranteed to make that no but generally you should be able with the right build some may need a little more help then others. And yes an engine that makes 1.7 vs 1.9 or more can be a huge power difference I'm just saying there is a general correlation between cfm and hp or we wouldn't use it at all.