AFR Heads

[273]

It will be awesome and flow like it told me it would on the flow bench.........

Please don't bring piston displacement, stroke and bore size not to mention piston speed into a discussion about head flow.

Depends what your trying to accomplish.

 

[Newbomb Turk]

What does that got to do with if cfm has much merit when it comes to performance, I started off saying I basically agree with but cfm has more merit then you seem to give it credit for.

CFM, velocity, port size are interrelated, if you know two of them you basically can figure out the third, you can't change one without at least effecting another. CFM obviously matters and for those that are not racing especially in a highly competitive race classes that has especially vague performance goals could do worse than shop by what a head flows.

CFM, velocity and port size are not akways interrelated.

I’ve said the before and I’ll say it again. More than once I flowed heads on my bench, fixed them and showed LESS flow and amazingly the engine made more power on the dyno and was quicker and faster in the car.

Don’t think I didn’t have a **** of a time trying to combine the guy his heads flowed less and made more power.

Now go ahead and explain that.

 

[Hysteric]

CFM, velocity and port size are not akways interrelated.

I’ve said the before and I’ll say it again. More than once I flowed heads on my bench, fixed them and showed LESS flow and amazingly the engine made more power on the dyno and was quicker and faster in the car.

Don’t think I didn’t have a **** of a time trying to combine the guy his heads flowed less and made more power.

Now go ahead and explain that.

Let me guess you made more power by improving the burn and used more of the air it actually ingested instead of just passing it through? Or better yet you improved cylinder fill increasing the trapped charge leading to greater BMEP?

Either way well done!

 

[273]

CFM, velocity and port size are not akways interrelated.


I’ve said the before and I’ll say it again. More than once I flowed heads on my bench, fixed them and showed LESS flow and amazingly the engine made more power on the dyno and was quicker and faster in the car.

Again not arguing it wouldn't

Don’t think I didn’t have a **** of a time trying to combine the guy his heads flowed less and made more power.

Now go ahead and explain that.

Still doesn't mean cfm has little/no merit.

 

[tvt59]

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.

Not trying to argue, and dynos are not a 100% accurate measurement of hp. The W5 engine we just finished. Before we ever put the engine together Brett said that it'd make more power than a AFR 245 SBC head. And he was right. From what I can gather most SBC with the AFR 245 head make 740-760 hp. The AFR 245 SBC head flows 350 CFM. My W5 heads don't quite flow 350 cfm. But the engine made 840 hp. Both of these heads flow about the same and the builds that I looked at with the SBC's were 14 to 15 to 1, solid rollers and good builds. But the W5 heads made more power. Some will say can't compare SBC to SBM but they are just air pumps.

 

[Hysteric]

Some will say can't compare SBC to SBM but they are just air pumps.

That's the problem they're not.

 

[273]

There partial air pumps.

 

[tvt59]

That's the problem they're not.

I know this. More air in , more exhaust out = More HP

 

[Newbomb Turk]

I know this. More air in , more exhaust out = More HP

Unless the mixture getting to the chamber is not good.

This is an example of more airflow making less power.

 

[tvt59]

Unless the mixture getting to the chamber is not good.

This is an example of more airflow making less power.

In my reference, I am assuming the tune is correct. But I also know what happens when you assume.

 

[ValiantRacing]

I have a friend and was helping him out with his small block chevy, the heads are AFR, and were ported many years ago, he thought they would flow over 300cfm, i flowed them on my bench at 260cfm, and when i told him, he thought i was crazy, put the car together its 350ci in a Nova, and it runs 9.80s, and i am sure he thought they flowed big numbers, he pulls the heads for a freshin, has them flowed buy someone else, and they go 265cfm, so i agree, big flow do not always mean fast ETs. or big HP.

 

[NC Engine Builder]

Well following up on this thread, I have a pair of the new AFR heads on my bench currently. They are not the speedmaster casting, they look nearly identical to the promaxx heads, although I do not know for certain which casting company does them. A few small differences I noticed is that they have 8mm guides, a better valve job and cnc blended bowls. That's all I see so far.

 

[PRH]

What are those going on?

Bought as bare or assembled heads?

If bare, and you’re going to use other than AFR valves, you should do a little build-up thread.

Do the valve seats look like they were done on a Newen CNC single point machine?

 

[NC Engine Builder]

What are those going on?

Bought as bare or assembled heads?

If bare, and you’re going to use other than AFR valves, you should do a little build-up thread.

Do the valve seats look like they were done on a Newen CNC single point machine?

They are not earmarked for any particular build yet, my supplier sent them to me because there new of course. As far as valve job, I'm not sure? I use goodson 3d cutters in a TCM25 machine, but I cant really determine how these were done, but the bowl blend is obviously CNC, not by hand or bowl cut. Supposed to use LS 8mm valves

 

[PRH]

If you look at the seats with a magnifying glass, the single point valve jobs look like really really fine threads.

AFR uses that type of machine on the non-budget line of heads…….but I’m not sure if the budget line gets the same treatment.
The TF Mopar heads(and probably all the others as well) also now get done on one of those machines.

 

[NC Engine Builder]

If you look at the seats with a magnifying glass, the single point valve jobs look like really really fine threads.

AFR uses that type of machine on the non-budget line of heads…….but I’m not sure if the budget line gets the same treatment.
The TF Mopar heads(and probably all the others as well) also now get done on one of those machines.

Interesting, I'll check that out closer.

 

[PRH]

I’ll be interested to see what you determine is correct for valves.
The reason I say that is all the AFR SBC and SBF heads use 8mm valves with radius lock grooves, but the groove isn’t located on the stem the way they are on LS valves.
They’re in the more traditional location, instead of right near the top.

 

[NC Engine Builder]

I’ll be interested to see what you determine is correct for valves.
The reason I say that is all the AFR SBC and SBF heads use 8mm valves with radius lock grooves, but the groove isn’t located on the stem the way they are on LS valves.
They’re in the more traditional location, instead of right near the top.

I dont have valves yet, but some are on the way, I'll let you know what I end up with.

 

[gzig5]

I'm sure you'll get to it later when you assemble them, but I'm interested whether they corrected the geometry at all by moving the shaft location. My ProMaxx didn't have a chance to get the PRW 1.6 SS rockers bolted down without moving up and away from the valves. Also be interesting to see how they flow on your bench vs. the PM 171s. I don't need another set of heads at the moment but nice to see another vendor with a hopefully competent SBM head option.

 

[NC Engine Builder]

I'm sure you'll get to it later when you assemble them, but I'm interested whether they corrected the geometry at all by moving the shaft location. My ProMaxx didn't have a chance to get the PRW 1.6 SS rockers bolted down without moving up and away from the valves. Also be interesting to see how they flow on your bench vs. the PM 171s. I don't need another set of heads at the moment but nice to see another vendor with a hopefully competent SBM head option.

I dont have high hope for the geometry to be any different, or the flow as cast to be much different than any other available china cast SBM head

 

[ValiantRacing]

They say heads are 175cc, does the extra 4cc look like it was takin out of the bowl?

 

[NC Engine Builder]

They say heads are 175cc, does the extra 4cc look like it was takin out of the bowl?

I haven't measured anything, but I will say the cnc bowl work looks much better than the SM. It could be a 4cc difference, it goes deeper and is more correctly shaped

 

[skrews]

From those pics they look nicer OOTB than the SM heads I started on. You got any pics of the exh bowl and chamber?

 

[NC Engine Builder]

From those pics they look nicer OOTB than the SM heads I started on. You got any pics of the exh bowl and chamber?

Yes sir

 

[NC Engine Builder]

Geometry with the liberty performance valves, is pretty much the same as all the other china heads. It will DEFINITELY require a correction kit to be optimal.