Intake/Exhaust headflow Ratio

igotyofire · Jun 16, 2005

Ok i can obviously see how this is somewhat important, but i want to know what it means in technical terms as far as how the engine is going to react. I would begin to think this would also be important in cam selection?

Im comparing afr165s, and the twisted wedge heads,

According to this the twisted wedges flow more , but the Afr's have the better ratio. Now i know more air = more power, but if you cant get rid of it in time wouldn't that affect the incomming air and also possibly not all of the exhaust gases escaping at once and there by limiting possible hp? So between the two what kind of cam design would one look for , for each application?

Im curious to understand this to see how possibly piecing the right pieces together to ensure more hp is extracted from motor

final5-0 · Jun 16, 2005

Hey Hey Hey

A tech Q with some substance to it!

We just might get a good discussion from this one and be able to learn a thing or two.

I can say I did not strain my brain on my current combo with the Q's your asking. I went with a custom cam so I'm not a lot of help with cam specs.

Hope you get a lot of replies.

Later
Grady

4Jenna · Jun 16, 2005

Sometimes you can have to much head also (to much flow for your combo) loosing low end. What are your plans for the car, when comparing heads cc, valve size and many other things come into play. The AFR165s are a 1.90 head with a nice CNC port on them outta the box, the TW are a 2.02 head box stock ports. What rpm range do you plan to shift this car, we still need much info.
As for the comparison in those 2 heads, the opinions will vary...I would hands down choose the TF if you are dead set on one of those heads. The TF have alotta meat on um (can port the snot outta um) and already come with a nice 2.02 valve.
One thing i also shoot for when building a combo that "matches"..i get my intake to flow what my heads do.

igotyofire · Jun 16, 2005

eades5.0 said:
Sometimes you can have to much head also (to much flow for your combo) loosing low end. What are your plans for the car, when comparing heads cc, valve size and many other things come into play. The AFR165s are a 1.90 head with a nice CNC port on them outta the box, the TW are a 2.02 head box stock ports. What rpm range do you plan to shift this car, we still need much info.
As for the comparison in those 2 heads, the opinions will vary...I would hands down choose the TF if you are dead set on one of those heads. The TF have alotta meat on um (can port the snot outta um) and already come with a nice 2.02 valve.
One thing i also shoot for when building a combo that "matches"..i get my intake to flow what my heads do.

definately makes sense. I ask these questions because i want to decide on a setup. Im finally saving up alot of money and will have funds for some decent work to be done. Well for my own personal goals i plan on piecing something together that i can daily drive reliably and i would like it to rev to 6000 probably (or as high and reliably as i can on a daily driven combo with stock block) and have more of a upper rpm pull. I plan on running it with my stock Cobra Intake. and probably shorty headers with offroad pipe.

Now i know when i ask for somthing like that its more of what i would want from the cam, and also i do know the lower cobra is restrictive. and for the time being i will be using the stock 3.08s somthing else which will be changed later and also affect the cam selection. This is why 1st i would like to choose a head. Not trying to have a afr vrs. trickflow thread but i would like to discuss the advantages in both heads

WhiteDevil · Jun 16, 2005

I also believe that those numbers with the Edelbrocks are the old castings. The new ones run right with AFR 165s very similar.

igotyofire · Jun 16, 2005

WhiteDevil said:
I also believe that those numbers with the Edelbrocks are the old castings. The new ones run right with AFR 165s very similar.

which heads? they have alot,heh

zenboy99 · Jun 16, 2005

I know that if you're running NOS or a turbo you want to have a head with a nice exhaust port. A bigger exhaust port for a turbo helps with spooling, and with NOS pumping through the intake you want to open up and favor the exhaust.

One reason besides price that I choose TW heads over AFR-165 is because they can be hogged out to flow well over 300cfm. If you ask a porter to do that to a AFR-165 head, he'll tell you to go out and buy some 205 or 225's.

As for a NA engine, I'm not sure what Intake/exhaust ratio is optimal. I suppose every porter/head company has their own theory.

igotyofire · Jun 16, 2005

zenboy99 said:
I know that if you're running NOS or a turbo you want to have a head with a nice exhaust port. A bigger exhaust port for a turbo helps with spooling, and with NOS pumping through the intake you want to open up and favor the exhaust.

One reason besides price that I choose TW heads over AFR-165 is because they can be hogged out to flow well over 300cfm. If you ask a porter to do that to a AFR-165 head, he'll tell you to go out and buy some 205 or 225's.

As for a NA engine, I'm not sure what Intake/exhaust ratio is optimal. I suppose every porter/head company has their own theory.

well i heard that with trickflows u need longer pushrods is that true? and that the afrs didn't, i do not know how much pushrods cost but i figured it will up the price a bit and they will both pretty much cost the same

wytstang · Jun 16, 2005

Also those Brodix flow rates are off on the intake side. They are also rated at @28" cfm and I think the other heads are being rated at @50" cfm.

bimmertech · Jun 16, 2005

as a general figure your exhaust flow for a n/a setup should be at least 75% of the intake flow. that doesn't mean that the better ratio will make more power. you can get the afr's with a smaller comb chamb which means more compression, which means more torque throughout the entire rpm range. as far as cam goes, custom is always better if your budget supports it, and if you are able to supply your cylinder head flow data to the cam grinder it is even better. with the head flow data they are able to dtermine the point at which the intake valve should close which is the single most important event in the entire process.

CManT1914 · Jun 16, 2005

Subscribing....

I am trying to figure out what a good cam selection would be with these heads (as well as Edelbrock). I started a thread about cams, but didn't get a lot of replies.

tmoss · Jun 17, 2005

I made that graphic a few years ago, and yes that is an older Eddy head test. The more recent ones show the Eddies (most street heads) flowing in the 225-230cfm range which is close to the AFR 165's flow. The big difference in the AFR/TW heads is in the runner length and cross section. The TW runner is shorter.

igotyofire · Jun 17, 2005

tmoss said:
I made that graphic a few years ago, and yes that is an older Eddy head test. The more recent ones show the Eddies (most street heads) flowing in the 225-230cfm range which is close to the AFR 165's flow. The big difference in the AFR/TW heads is in the runner length and cross section. The TW runner is shorter.

so which head in out of the box form has the more potential to flow better at upper rpms without any headwork and without taking a cam into consideration?

tmoss · Jun 18, 2005

Browse around this site, it has head flow data and other informative stuff....

http://www.jason.fletcher.net/tech/tech.htm

Intake/Exhaust headflow Ratio

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